Printer and Photocopier Troubleshooting and Repair Collection

Version 2.79 (13-Feb-13

Copyright © 1996-2013
Samuel M. Goldwasser
--- All Rights Reserved ---

For contact info, please see the
Sci.Electronics.Repair FAQ Email Links Page.


Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied:
  1. This notice is included in its entirety at the beginning.
  2. There is no charge except to cover the costs of copying.



Table of Contents



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    Preface

    Author and Copyright

    Author: Samuel M. Goldwasser

    For contact info, please see the Sci.Electronics.Repair FAQ Email Links Page.

    Copyright © 1994-2013
    All Rights Reserved

    Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied:

    1. This notice is included in its entirety at the beginning.
    2. There is no charge except to cover the costs of copying.

    DISCLAIMER

    Some of the procedures described in this document require access to dangerous voltages, hazardous laser radiation, moving mechanical parts, and other potential risks to personal safety and damage to equipment and property. The authors and contributors to this document will not be held responsible for any direct or collateral damage which might result from following the suggestions or recommendations contained herein including but not limited to: shock, burns, electrocution, vaporization, meltdowns, torn flesh, destruction of the equipment, and local or planetary wide power disruptions or implosions.



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    Introduction

    Most of the articles in this document have been compiled over the last few years from postings on the USENET newsgroup sci.electronics.repair. I cannot vouch for the accuracy of all of the recommendations they contain but have edited out anything I felt was totally bogus. I apologize if your response is not here - it could have been that I missed the posting and will welcome contributions.

    Note that many of the problems and solutions are listed with respect to specific models. Even though your model and problem may not be included, there is a good chance your problem is covered but with respect to some other model printer or copier. Therefore, search for a generic description of the symptoms and you may get lucky.

    Since the operation of laser printers and photocopiers is very similar, check both chapters to see if your problem is covered when dealing with either type equipment.

    There is also a chapter on fax machine problems though it is pretty sparse at the moment.

    Eventually, this document may be expanded into a full "Notes on the Troubleshooting and Repair of Printers and Photocopiers". For now, be happy that it exists at all! :-)

    As always, comments, suggestions, and corrections are welcome.

    Portions of this document also appear at PrinterCartridgesInk.com under "Printer Advice". As far as I know, this was done without my permission but since he included the appropriate attribution and copyright notices, I'm not complaining. The formatting may even be a bit better. :)

    See the document: Troubleshooting and Repair of Consumer Electronics Equipment for general information on tools, test equipment, tips, techniques, and much more.

    SAFETY

    Also see the document: Safety Guidelines for High Voltage and/or Line Powered Equipment.

    While printers are not generally considered dangerous pieces of equipment (compared to TV, monitors, and microwave ovens, at least), some types - laser printers in particular - present a variety of hazards that should not be underestimated. In addition, photocopiers - particularly larger high speed machines - need to be treated with great respect while servicing.

    There are minimal dangers in servicing most printers. However, there may be exposed line voltage near the line cord and long hair or neck-ties may be sucked in along with paper! Laser printers have their lasers but these are generally located such that accidental exposure to the beam is minimized. The toner in copiers, plain paper faxes, and laser printers may be harmful if inhaled and is a potential fire/explosion risk if carelessly vacuumed. Each of these possible safety issues is discussed below with additional specific information in the chapters for the equipment to which it applies. All in all, working on printers is relatively low risk.

    The first set of items applies to all line operated printers:

    The following apply to laser printers and photocopiers:

    And finally, for laser printers and laser photocopiers:



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    Printer and Photocopier Technology

    Dot matrix printer operation

    These are the only type of impact printers still in wide use. A set of steel pins - typically between 9 and 24 - strikes the paper through a fabric or carbon film ribbon. The pins are activated by solenoids which are controlled by the printer's control logic. Multiple passes may be used to increase the effective number of pins and improve print quality (letter versus draft mode).

    For text, an internal character generator (ROM) converts ASCII codes to pin firing patterns. For arbitrary graphics, the actual bit map is read out and used to control the pin drive.

    The paper, carriage, and sometimes ribbon movement use stepper motors. These, their drivers, or interconnect cables, are common problem areas.

    Daisy wheel printer operation

    These may still turn up at yard sales and flea markets but have virtually disappeared due to slow speed and limited flexibility with respect to graphics. In their defense, for basic text, their quality is superb for a low cost printer.

    Instead of pins, these use a wheel with all the possible characters molded on 'leaves' around the perimeter. The wheel spins to the correct character position and a hammer than taps the leaf to impress the character (via a ribbon) on the paper. Carriage and printhead movement is similar to that of dot matrix printers.

    (From: Peter (hedgieus@yahoo.com).)

    Some history/trivia:

    The daisy wheel printer (interestingly) was patented before World War II! It was GE or a GE engineer, but only commercialized by Diablo, which was later bought by Xerox in its expansion to California. Later spinoff was Qume, and then lot of companies got into it, some Japanese, some local (California). Daisy wheel technology was killed by the laser printer becoming cheap and having better quality. Original impetus for it was speed: IBM Selectric was able to print at 10 char/s (good for 110 baud modems!). It moved the whole ball (big inertia). Daisy wheel only moves one spoke, (to print one character) and got 30 chars/s.

    Near the end of the era, 'on the fly' printers got as fast as 80 char/sec.

    Ink-jet printer basics

    (From: Tony Hardman (AHED_CIJ@f54x19.demon.co.uk).)

    There is a US publication called 'The Hard Copy OBSERVER' from Lyra Research Inc. Tel: (617) 322-0708.

    This discusses the latest technologies and who does what. It may not cover the print head technology very much but is a good read if you are into print technology in general.

    There are many companies that sell variable print processes. One I have heard of is RALFLATAC. They do a brochure that does an excellent brief of most technologies available for printing. They have UK (and many other sites in europe) and US sites. UK Tel 01732-583661, US Tel (704) 684-3931.

    I have no idea if you can easily get copies of either publication from them so here goes a very very brief description.

    Ink jet printing has two main types, continuous ink jet (CIJ) and impulse printing (DOD) (drop on demand). Each of these can be a single jet, or an array of jets.

    A primer on priming

    The priming station of a typical ink-jet printer (e.g., HP DeskJet 500C) includes a rubber seal ('boot') and small pump to actually suck on the end of the print cartridge to free up nozzles (there are 50 or more in a typical print cartridge) that have dried up or become clogged. It may fire all the nozzles at some point during this process as well. It also includes rubber 'flappers' which the end of the cartridge pass over to wipe off excess ink.

    Priming and cleaning are normally done automatically upon power-on and possibly between pages. However, additional cycles may be needed at times.

    With the water based ink, even if the printer is powered off properly which seats the cartridge(s) on a rubber seal, some evaporation occurs so priming will often be needed after it sits idle for a while. Note: Don't kill power to an ink-jet printer as soon as your printout pops free - it needs to position the printhead and cartridge(s) on the rubber boots. Wait until the printhead stops moving and clunking. Some (older) printers don't even have a seal in which case letting it sit idle is even more likely to result in problems.

    If there has been ink spilled into the priming area, it may clog up the little hose connecting the priming station to the pump - I have used a wooden toothpick to clear the hole though this may be risky if it should break off. With care, a wire rounded off at the end so as not to puncture the tubing can also be used. Complete disassembly and washing of the parts is probably the best but is probably a pain.

    A bit of ink-jet history?

    (From: John Nagle (nagle@netcom.com).)

    The original ink jet printer of this type was the Teletype Inktronic, which introduced the concept of video-type distortions to printing. It appeared around 1970, and was so bad nobody tried again for years.

    (From: Tony Hardman (AHED_CIJ@f54x19.demon.co.uk).)

    I guess that is why it was used in industrial applications I guess. Were the 'video-type distortions' a deliberate feature or just a coincidence of how they turned out?

    Who are/were Inktronic???(apologies to anyone connected with them) I guess that may have been spin off development from some work contracted out by IBM, but it was so....?? (costly/low res/unreliable - choose one) they lost interest. Although one of the very early machines still runs well on a textile mill. It had a large number of jets side by side, and may be multi color too. I've only seen the patents so don't know exactly what it looks like.

    I thought original ink jet printer was a chart recorder developed in the last century. It was just a nozzle on deflection mechanism, and was not modulated so it was always printing. It was a lighter mechanism than actually trying to move a pen and so had some performance advantages over other technology available at the time...

    The same reason CIJ still sells world wide, even when high resolution DOD is biting at its heals.

    Inkjet types (at least from a Xerox perspective)

    (From: Peter (hedgieus@yahoo.com).)

    Here are history/trivia. (I used to work at Xerox marking technology group, working on ink-jets and daisy printers.)

    Response times of resistance heater elements in ink jet printers

    The ink drops that make up the 'image' on the paper from an ink jet printer are expelled by microscopic resistance (thin film or the like) heaters with response times in the 10s of microseconds if I recall correctly. When living in the macro world, it is often counterintuitive to realize that a resistance element can have such a fast thermal response.

    (From: John Eaton (johne@vcd.hp.com).)

    The trick is that a lot of the energy that you pump into the resistor leaves the printhead with the fired dot. One way to detect Out_of_Ink is to mount a thermistor on the printhead and watch for a sudden rise in temperature as you are firing.

    How many colors can an ink-jet printer can produce?

    "I use a HP680C in the office, and it have two cartridges, one for black and one for color (yellow/cian/magenta?). If the printer fire one drop of each ink at a given point, we can have only 6 different colors (ignoring white and black). If it can fire two or more drops at a given point, maybe we can have more colors, but I suspect that the printer use this to control quality of the presentation, not the number of colors. Anybody knows for sure? With dithering it can make more colors, with reduced resolution."

    Like most print processes you only have a limited selection of inks to use. Full colour can be derived from three primary colors, just like a monitor. For monitors, these are Red, Green, and Blue because monitors emit light resulting in an additive color process. Inks, on the other hand, absorb light so printing is a subtractive process. The resulting inks should then be cyan (blue+green or -red), magenta (red+blue or -green), and yellow (red+green or -blue).

    Therefore, the colors used in common ink-jet printers are not really capable of producing true full spectrum photorealistic quality results since they are red (not magenta), blue (not cyan), and yellow. These are optimized for nice saturated primary colors when used independently. Also see the section: Why are red, blue, and yellow inkjet primaries?.

    In addition, the combination of the three primary colors should be capable of being combined to produce black but due to misregistration and the pigments used, this black would be somewhat muddy and brown. Therefore, a separate black ink cartridge is normally used for black printing.

    (From: Tony Hardman (AHED_CIJ@f54x19.demon.co.uk).)

    With printing there are more problems than solutions and I do not know which method HP use in their printing.

    If you can vary the drop size, you can change the drop spread on the paper. This can be done by firing bigger slugs of ink, or multiples of the drop at the same position. As you can figure the ink will either spread and make a bigger drop, or stay the same size and become denser. Depending on the resolution you want these could both improve colour density. This depends on two key components.. The ink, and the paper.

    The problems with laying down multiple drops on paper is that if you do a large block the paper will curl up and the overall image becomes worse. This is why you can pay 1$ a sheet for 'quality' paper.

    Another problem with this is speed. Firing two drops in the exact same place is difficult... Unless the head is stationary but that is not good either. You may notice that most DOD printers in high resolution mode do a number of passes over the same place. This does allow dithering and other techniques for resolution / colour enhancement. They usually only print while going in one direction for improved mechanical control.

    In the 1600 printer there is a heater to assist with the drying times and reduce the curling problem.

    Inks are a problem too. They can dry at different times because of the different dyes used, or they may not mix how you expect if you place two colours on top of each other. Its only ink ... but to get the best balance of surface tension, drying time, viscosity, colour, stability.... and more is not as straight forward as it might seam. I have noticed that the water based inks are improving, and there are some that do not run if they get wet (after drying on the paper).

    I think the spec in your manual may suggest what method they use.. The printer resolution (best) is 600dpi (I guess), and I recon the best full colour resolution is lower. Also the print head is only 300dpi so you must do two passes to get 600dpi black (single black ink cartridge). This suggests a partial step of 1/600 inch between the passes. What happens when you print black using the colour head? How many passes, how much slower? The resolutions quoted may also be 600 * 300, or what ever. If they make blocks of colour from a potential 600dpi machine, the resultant image is probably only 75dpi (possibly less). This still might be called 600dpi, because the drop placement uses this resolution, but it is not 600dpi at full colour. The resolution of quality picturers / poster is several thousand dpi, but not a variable image (not ink jet).

    In the Lyra publications they did publish the real print head specifications for the machines they review. They also include some of the methods of colour printing.

    After all this I have noticed that I have not answered the question of how do HP et all get their colour resolutions. All I have mentioned is a few of the parameters that the designers have to deal with.

    Why are red, blue, and yellow inkjet primaries?

    For a subtractive printing process, the 'optimum' primary colors for a 3-ink system would be closer to magenta, cyan, and yellow. However, these are not generally used. Why?

    I don't know the precise answer but it is no doubt a tradeoff between cost and which colors are used most often. For non-photo printing, the straight red, blue, and yellow are far more useful since they can be use by themselves or in simple combination to produce a wide range of vibrant, if not realistic colors. For example, pure red is far more likely to be used for simple graphics than magenta. To make something that looks like pure red using magenta and yellow requires a precise combination - not easy to do with an inkjet printer!

    About inkjet printer ink

    No, you can't refill your HP DeskJet cartridges with fountain pen ink!

    (The following is from someone who also sells inkjet refill kits so this may not be an entirely unbiased writeup.)

    (From: John Connolly (toner@idirect.com).)

    There are at least 10 ingredients in inkjet ink, starting with triple distilled, de-ionized water, dye or pigment color of a known particle size, humectants such as glycol to minimize evaporation (and head clogging), surfactants to balance the surface tension and paper wetting, resins to get good paper adhesion, biocides and fungicides and buffering agents for the correct pH. These considerations ensure that properly reverse engineered inks not only work, but produce a print comparable to the OEM. For printers like Epson, with fixed permanent print heads in the printer, expensive repairs are also avoided.

    To make matters worse HP has rigged their most popular black cartridges for the Deskjet 500 & 600 series to curb refilling, with air bladders, constantly changing maze/ venting assemblies at the bottom, and logic to change the signals to the micro-resistor jets on the 3rd or subsequent reinstallation of the cartridge. The color cartridges for these MUST be refilled before air locks occur, particularly in the yellow chamber.

    Some people still manage to get an acceptable refilling success rate with these Deskjets, but we feel it is a bad introduction to refilling for the first time refiller. Deskjet series 700, 800 & 900 are better bets to refill.

    But, the current Lexmark, Canon, Xerox and Epson cartridges are by far the easiest to refill.

    Image Control's refill kits for the Canon 4000 series refill the BCI-21 black 40 times, or the BCI-21, 12 times EACH color.

    More details on inkjet inks, a description of our refill kits which are larger than most offered, references and printer/cartridge tips are available at Image Control's Web Site.

    Laser printer and photocopier operation

    Copiers and laser printers have a lot in common. The major difference is in how the image is formed on a photosensitive drum:

    Beyond this, copiers and laser printers are nearly identical (at least in principle) except that copiers use a positive process (dark areas in the original result in marks on the paper) and laser printers commonly use a negative process (a spot of light results in a dark mark on the paper).

    The most sophisticated machines are now actually scanner-laser printer combinations with buffer memory so that multiple copies can be made without rescanning the original, sorting and collating is more flexible, scaling and rotation can be done digitally, and other features not possible with simple copiers.

    (Portions from: Copenhagen Cowboy (cowboy@fastlane.net).)

    The photosensitive drum is the heart of the laser printer or copier. In larger machines, it may be a separately replaceable unit. In most laser printers and smaller copiers, it is part of the 'toner cartridge' and is a throw-away (or may be recycled).

    The drum is coated with a photosensitive material which has an extremely high resistance when in darkness. It's resistance drops to a low value when illuminated.

    All of the following takes place as a continuous process as the drum rotates. Note that the actual photosensitive drum in most copiers and laser printers has a circumference that is much smaller than the length of the printed page. Therefore, only a portion fits at any given time and the charging, exposure, transfer to the paper, cleaning, and erasing is a continuous process:

    That is the basic process. Many variations are possible and depending upon the machine and manufacturer, some of this may be a little different. Where a (disposable) toner cartridge is used, many of these components are replaced with the cartridge - typically the drum, toner itself and developer (usually combined into a single powder), developer magnet (really neat!), cleaning blades, some of the corona wires.

    There is also some photocopier information at:

    Laser printer operation summary

    (Portions from: Zaki (zg@ix.netcom.com).)

    In general the principle of electrostatic laser printing is as follows:

    1. Charging a photoconductive selenium (or other) coated drum.

    2. Discharging the drum with the laser steering engine in accordance with the input image rasterized pattern. (the laser is modulated to generate a predefined pixel pattern on the face of the drum - the focal plane).

    3. The rotating drum attracts toner to the charged pattern (latent image) generated by the laser.

    4. The toner is transfered from the drum to the moving papaer to generate a full image.

    5. The paper carrying the toner moves through the heater to fuse the toner to a fine non-erasable image.

    The laser steering engine is combined of the following components:

    Cleaning and Handling of Photosensitive Drums

    Where the drum is located inside a replaceable toner cartridge, there is no need for special handling. However, where the drum is a separate unit, the following applies. Or, if for some reason, you need to disassemble (gasp!) a cartridge:

    (From: David Kuhajda (dkuhajda@locl.net).)

    Whatever you do, do NOT use alcohol on an organically based drum, it will ruin it. The alcohol causes the material to crystalize. I use to do copier service and this was stressed a lot by the manufacture as they switched from the old selenium drums to the new opc drums. Direct sunlight will immediately destroy the drum. A couple of minutes under normal lighting is no problem, just place it in a dark area and put a black cloth over the top of the drum while it is out. If you are replacing the drum cleaning blade or cleaning the crud off the blade, make sure you powder up the drum completely and the blade before reapplying power. The toner actually is a slight lubricant and the rubber cleaning blade directly on the drum will also ruin it. Just print a few low text copies after reassembling to allow the blade to reseat properly.

    (From: hapticz@email.msn.com.)

    Short periods (less than 5 min) under fluorescent lighting is safe.

    Direct sunlight kills them immediately.

    Just have a clean brown paper bag to shove it into while it sits on the table outside the machine.

    Often more damage is done to them physically during insertion/removal. just be careful.

    Xerox used to clean the 10" diameter drums with 90% isopropyl alcohol and some kind of "Kim Wipes" in our office, that was years ago though.

    Book on laser printer maintenance and rapair

    (From: Michael (ncacaver@aol.com).)

    Get the book: "Easy Laser Printer Maintenance and Repair by Stephen J. Bigelow".

    Your local library should have it or be able to get it. Stephen J. Bigelow has several other books on printer repair, both laser and non laser types. All are very good.

    Discussion on laser diodes in laser printers

    "I just acquired the optics from a dead laser printer and have been trying to understand it. There are two functions I have yet to grasp. One is something which it has but for which I see no need. There seems to be a heater (Contains mica) and a thermometer, with PCB markings like "T1" and H2" or something similar. If these the laser is temperature controlled, why? There seems to be a control photodetector to monitor the laser diode so temperature control appears like overkill unless the photodiode itself has too much temperature dependence and the drum exposure is very critical."

    (From: Jonathan M. Elson (jmelson@artsci.wustl.edu).)

    There is a heater inside the fuser roller. This is what melts the toner into the paper. It is thermostatically controlled, and then has a safety thermostat in case the control fails.

    There are two photodetectors for the laser. One compensates for dimming of the laser over years of use, the other picks up the beam at a particular angle of the polygon mirror, and synchronizes the raster electronics to the polygon rotation.

    "The other thing is something I cannot find, the aperture defining the nice well-formed pixel. So far I must admit the study has been a bit superficial but the aperture ought to be pretty obvious if there is one!"

    The laser is the aperture. With an optical path of 0.5 m or so, the laser is a pretty good approximation of a true point source. A simple lens makes it look like a very good point source.

    "Finally, how are the correction lens made? They look like slices out of the middle of some fair sized lenses, but that would be a very wasteful way to make them. Can they be diamond formed to nearly the final shape and with such good finish so only a simple polish completes them. Grinding the old-fashioned way on a sliver of glass looks doomed to generating all sorts of defective approximations to a sphere. (As far as I can tell they are glass, or some wonderfully hard plastic I would like to know more about!) Can they be molded to sufficient precision? (The sides are ground or sawn.) Thanks to anyone who can bring me up to date on lens fabrication technique."

    I think they mold these lenses to near correct shape, then grind and polish to the desired aspheric shape with specialty machines for that purpose. (Note that almost all eyeglasses are aspheric for astigmatism correction.) Yes, these lenses are glass, I've had a few printers apart myself.

    Types of toner

    (From: Lionel Wagner (ck508@FreeNet.Carleton.CA).)

    There are two basic kinds of toner: magnetic and non-magnetic. If your laser printer has a Cannon 'engine' it most likely uses magnetic. NEVER use the wrong type. The imaging process is extremely delicate and specific toners are important. Use of toner that is slightly different could result in all black or all white copies.

    So you put in the wrong type of toner?

    "I have a 3M Model 6312 copier. I believe it is a re-badged Lanier. I didn't pay much for it but it worked well. When the toner warning light came on, I made the mistake of adding the wrong kind of toner. I removed the wrong toner as much as I could by vacuum. Is there anything I should do before adding the right type of toner? Did I do serious damage to the system? What to do if the warning light remained on even with the right type of toner added? Any suggestion will be greatly appreciated."

    (From: Lionel Wagner (ck508@FreeNet.Carleton.CA).)

    If your copier uses non-magnetic toner, it is mixed with iron powder, called the Developer. Both have to be removed and all residue vacuumed out. If the copier uses magnetic toner, less of it will remain in the machine. Try to get as much as possible out. Do not scratch the roller on which the toner sits.

    WARNING: See the section: Warnings about vacuuming laser printer toner before using a household vacuum cleaner to do this!



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    Dot Matrix and Daisy-Wheel Printers

    So you took your printer apart....

    "I stupidly took apart my Panasonic KX-P1123 to attempt a head swap (the cable was too short!), now that it's back together it just beeps when I try to print. The only things I touched were the rod that the head assembly slides on and the toothed belt also had to come off (I don't think it's a timing belt.. there's no clear markings suggesting that). When I try to print, the head moves to the center, there's no pin action and it starts beeping at two second intervals (and won't stop). It's not the paper sensors because they seem to work properly...any ideas?"

    (From: Filip M. Gieszczykiewicz (filipg@repairfaq.org).)

    Greetings. A few:

    1. Make sure you didn't trap and crimp any wires .. there SHOULD be a 'Column 0' sensor - either a photo-interrupter or a switch. The print head will activate it during the self-init.

    BTW, move the carriage all the way to the right, close the cover and turn it on - does the print head move or does it just sit there and beep?

    1. Ensure that you have the ribbon cable correctly hooked up between the printer & head .. some [smarter] printers can tell... I am not sure about that one, but some printer have an optical (IR) sensor that detects ribbon presence (or am I spoiled with fixing $$$ printers? :-)

    2. This should be obvious - but does the print head move FREELY all the way from the left to right and back? Don't forget to oil (not too much!) the rails!

    3. Did you reconnect all the cables? Is the front-panel (display+buttons) attached?

    More depends on the answers and results of the above. BTW, most newer dot-patrix printers just need 2 screws to be removed to release the head. I know the Epson LQ-1050 works like that (and many of that Stars as well). Anyones needs parts from the former? I have one with a dead head (and it's not economical to repair).

    Print head repair

    "I have a few Epson dot matrix print heads with stuck or sunken pins. Does anyone have experience with disassembling these things for cleaning/repairs? It looks like you just have to pop a few clips to get them apart."

    (From: Chris Serrano (brace@loop.com).)

    I resurrected one by hanging it pins downs in an ultrasonic cleaner. A lot of old dried up ink floated right out and the stuck pin became obedient again.

    (From: Filip M. Gieszczykiewicz (filipg@repairfaq.org).)

    Greetings. If one does not have the use of an ultrasonic cleaner, I have found a different way to get these suckers working again.

    Go to your local plumbing store and look in the chemicals department for 'CPVC-PVC-ABS CLEANER' (used to clean plastic pipes). This stuff is a combination of groovy chemicals Methyl Ethyl Ketone and Acetone. It will 'melt' most plastics so be sure the print-head's any plastic parts are safely taken off.

    Pour some of this stuff into a GLASS container and put the print head, business-end first, in it and leave it there for a few minutes. When the stuff turns dark-purple (all the ink and goo from the print head) you are done. Let it dry (few minutes) and then oil it with LIGHT OIL. Note: Do NOT use WD40 - we're interested with something that sticks around for a few months... WD40 just leaves a 'protective layer' with almost zilch lubricating properties (it's a Water Displacer (WD), after all).

    I have done this for a few DataSouth DS-180, Infoscribe 1000s, and Xerox [monster] printers that see a box of 132 column paper a month (each) for a number of years with excellent results. Note: YMMV... these printers have rugged print heads (7/9 pin)... I don't know how a 24-pin Made-in-China feather will respond.

    Ribbon does not advance after replacing flex-cable

    Have you actually confirmed that your 'new' ribbon cables are making proper contact - with an ohmmeter? Assuming that the thing worked better before the cables were cut, then there are only two possibilities: your replacements aren't quite right or something was damaged by the 'event' or through later actions.

    Print head stepper

    Confirm that you simply don't have bad solder connections around the plug to the motor. This is common in printers and will result in erratic or incorrect motor movement.

    (From: Ralph Wade Phillips (ralphp@gcstation.net).)

    What's common in some older Okidata 32x's and 39x's is that the lithium battery *above* the stepper driver will spring a leak, and drop the lithium compound onto the legs of the stepper. I do not know for sure if it's corrosive, conductive, or just plain nasty, but it kills the stepper deader'n'snot.

    I'd LOVE to find a replacement - I've got a service customer that has about 2,500(!!!) 320's and 321's in the field, and I am not looking forward to having to exchange all those boards over the next several years.

    Motor driver blows fuses

    The following was in response to a dot matrix printer blowing the power fuse whenever the paper advance motor was driven. A 74LS273 was getting hot as well:

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    I'm going to guess (based on what I've seen in other printers) that there's a set of power transistors (either H-bridge drivers or 1 per coil, depending on the motor) that drive the stepper. These transistors are driven from the printer's microcontroller via an output port - in this case the '273.

    Now, if a TTL chips is getting very hot, then either something is drawing too much current from it, or something is overvoltaging one of the pins. A particularly unpleasant failure mode is when a PNP power transistor, with the emitter tied to the V++ rail (the 20V + rail that supplies the motors) decides to short and apply said voltage to the output of whatever device is driving it. If you're unlucky, the next stage is that the output port device breaks down as well, and the CPU data bus gets 20V or more on it. The result is blown chips all over the printer. Please don't ask how I found that out ;-)

    My guess is that there's at least one shorted transistor in the stepper motor drive circuit. If the system uses an H-bridge driver (an equal number of NPN and PNP transistors) then if one transistor shorts, its companion is connected across the power rails. When it turns on, the supply is effectively shorted.

    I think you'll have to trace out the driver circuit for the stepper motor. Figure out what drives what. Test the transistors, and then replace the defective ones _and_ that '273, which is probably now blown.

    Ribbon on electronic typewriter does not advance

    "My wife has a "Smith Corona" Model SD800 electronic typewriter that will not advance the ribbon. Everything else seems to work fine. We have been unable to find a local repair for this unit. I think I can fix it with some advice from someone familiar with these machines."

    Can you determine if it is a mechanical or electronic problem? For example, with the ribbon removed, does the gear or post that drives it appear to try to turn or not at all?

    Modern electronic typewriters are a combination of keyboard, microprocessor, and printer. Therefore, the same sort of troubleshooting approachs can be used as for computer printers.

    Common electronic problems include bad connections to the motor that advances the ribbon (cold solder joints, cracks in traces on flex cable to carriage), bad motor driver chip, or bad motor.

    Mechanical problems include stripped or broken gears, misalignment preventing advance mechanism from engaging, and defective ribbon cartridge.

    (From: Roger D. Waddell (rwaddell@peachnet.campus.mci.net).)

    This problem is usually caused by a broken 'E' clip on the bottom of the print hammer solenoid. The clip holds on a lever that works in conjunction with the ribbon/correction feed solenoid near the right front of the print carrier.

    When the clip breaks, the lever falls out of position and never trips the lever that assists in feeding the ribbon.

    I have seen this problem many times!!

    Apple Imagewriter II squeal

    "My Imagewriter II, after many years of faithful service (~8), is starting to squeal. It squeals when the carriage moves. It still prints perfectly fine, but....a new noise can only mean trouble. Does anyone have any experience with this problem and his solution? I imagine it would take only a drop or two of lubricant. But where?"

    (From: Chris Jardine (cjardine@wctc.net).)

    I would suggest that you might have a problem with the ribbon mask. A few years ago I was the service manager at an Apple dealership. I can't tell you how many ribbon masks I replaced for many different problems, including wierd noises. It could also be a problem with the carriage drive motor. I can't remember which side of the printer it is on, but, it is below the gear/pulley that drives the toothed belt. You might try some very fine (maybe silicone) oil there and you might want to clean and then re-oil the carriage guide bar (the shiny round bar) and the bushings on the carriage that ride on the bar. The only other possibility would be a problem in the gears below the ribbon that are responsible for driving the ribbon.

    Compaq Pagemarq 15 printer service mode

    (From: Darren Mckillop (Darren.Mckillop@gecm.com).)

    Try powering on while holding escape, this will put you into service mode. Press the up arrow to start the engine test, if this works you may have a problem with the xerox controller board.

    Try disconnecting all the n/w cables and reseating the cables on the system board. Remove this by the two thumbscrews at the back and slide out as far as you can then pull the cable off.

    I have a Compaq Pagemarq 15/20 service manual that I am selling, but I am in the UK, where are you?

    Epson FX-286e printer problems

    "I just received the above printer in a non-working condition. It exhibits the following symptoms:

    When power is applied, the head appears to try and move, but will not unless you manually get it started. Then it goes to its home position. You then hear three beeps, and nothing else can be done to elicit any response from the printer. The power LED comes on, but the paper-out will not, regardless if there is paper installed or not. The paper detect switch is working properly (checked with ohmmeter by inserting/removing paper while across switch). Also, I hooked up a resistor and +5 V to the paper-out LED, and it lit up ok. I have also mapped out the stepper motor leads, and resistance checks show that it appears to be ok.

    MY question is if perhaps I lost one of the outputs for one of the stepper phases. The controller seems to be one large power-ic from what I've traced out."

    Could be. Do you have a scope? You could check the phases.

    "I know if you keep voltage across one phase, you can lock a stepper. If you lose power to one phase, will the other phases keep it going provided you manually start it like I'm doing?"

    Also check for bad connections to the stepper from the logic board - I have seen these on printers.

    It doesn't explain your other problems, however. Once initialized, even though the print head doesn't move properly, I would expect the printer to work in other respects.

    (From: Joe Wagg (jwagg@fs.cei.net).)

    The 3 beeps tell you there's a carriage error, probably from an incorrect number of steps needed to reach the home position. Since you've already checked the motor, the next step is to check the motor drivers. Using a meter with a diode check function, put the red lead on ground and the black lead on each phase coming from the board (disconnect the motor first). The readings should be within 20 percent of each other, not open or shorted. Also make sure the motor, pulleys, and carriage are all relatively clean and move freely. The other symptoms are caused by the carriage error, which halts the cpu to prevent damage. Clear up the carriage error and the other problems should go away. You should also make sure that all socketed chips are properly seated and don't have dirty contacts.

    Paper debris clogging Epson LQ-570

    "I have an Epson LQ-570 series dot-matrix printer that has developed an intermittent paper feed problem over the past year or so. It uses a push tractor for sprocket-feed paper, and paper tends to bunch up under the platen. There doesn't seem to be an obvious way to remove the platen to see what the paper's catching on, indeed the FAQ on Epson's website says it can't be removed, and to bring it in to the dealer for repair."

    (From: Asimov (Asimov@juxta.mn.pubnix.net).)

    Remove everything that is normally accessible. Then flip the printer on its back and play a vigorous drum roll all over it. This should dislodge a huge amount of "holes". Didn't you always wonder where those perforations went? Well, some of them make it into clogging up under the platten.

    Flip the printer on its side and with a thin brush dust the remaining grime away. If the jam didn't clear up you might try manually inserting a stiffer paper (postcard, greeting card, etc) a few times before dismantling the platen assembly any further.

    IBM X-24 Proprinter print head jumps around

    "Got a problem with a real nice 24 pin dot matrix printer I bought used. Was working fine for awhile then all of a sudden it will be printing fine an the printhead intermittently will jump to the center of the carriage and start printing from there. Also, when you turn it on, many times the printhead jams over to the right side of the carriage and the gears grind and you have to cycle it on and off to get it to start up right. Then you now almost for sure it will have problems printing. Help, any ideas? Do I just change a control chip? How do you scope out something like that? Can I get a manual somewhere? I want to keep the printer."

    Also check for bad connections. If the printhead motor is a servo (DC instead of stepper), you have an intermittent feedback problem, again could be bad connections or bad parts.

    (From: Ralph Wade Phillips (ralphp@gcstation.net).)

    First off, have you changed the RIBBON? Second, clean the print head carriage rails. They need a VERY LIGHT coat of VERY LIGHT oil, then wiped clean.

    Usually, when I see this, either the printer is just plain wore out, or the ribbon is snagging. Since the ProPrinter family drive the ribbon off of the carriage drive, if it ever snags, you'll get these symptoms.

    NEC P5200 Printer problem

    "I have a NEC printer that has an intermittent CE (ribbon cartridge empty) problem, only the cartridge is new and good. Anyone knows what senses this condition and what part could be affecting this? NEC wants $20.00 just to talk to me. Thanks for any help."

    (From: Paul Weber (webpa@aol.com).)

    Look at the old ribbon. Does it have a short piece of transparent tape at the end of the ribbon? If so, the printer probably has an optical end-of-ribbon sensor; a LED/phototransistor pair that looks through the ribbon. Does it have a short patch of aluminum foil tape (probably on the back side of the ribbon) ? If so, there is probably a pair of contact fingers that rub the back of the ribbon as it feeds. Look for bent contacts or debris in the ribbon holder mechanism.

    Look at the ribbon holder mechanism in the printer. Is there switch or contact pair that could sense the motion of the ribbon cartridge's feed reel? If so, check for free movement and cleanliness. Does the ribbon holder move with the printhead on this machine? If so, check that the ribbon cable connecting the carriage with the remainder isn't damaged and is connected properly at both ends.

    OKI Microline 391 Elite Problem/Error

    "I am having a problem with a OKI Microline 391 Elite. I opened it up and cleaned out the dust and paper from inside. On putting it back together and powering up, The SEL light, the COURIER font light, LW and 10 cp light are all flashing and the stepper motor for the platen is jigging back and fore about once every 3 secs."

    (From: Glenn Allen (pclogic@xtra.co.nz).)

    These printers generally need just a clean out and put back together.

    I would try to reseat the main logic board first, also try cleaning the edge connectors. There is a plastic joining bracket between the print head cable and the main logic board.

    If you are getting bad carriage movement then check that the carriage can move freely back and forth, also check the black teethed guide lying on the bottom for clogged teeth. The print head ribbon can be removed for better testing. if the carriage doesn't move freely then you may need to adjust it's position by loosening the two screws on either side of the print head carriage and then adjusting back and forth until good movement is achieved.

    Star SD15 printer self-test problem

    "This printer has a problem I am lost with. When I power it up and attempt to have it perform the self-test printout (FF on power up), the print head moves back and forth, the paper feeds, but the pins don't actually fire. However, if I connect the printer to a computer, the printing is just fine."

    You are complaining? :-) Usually, it is the other way around!

    (From: Ralph Wade Phillips (ralphp@gcstation.net).)

    Eh? On the SD-15, the FF SelfTest is for checking HEAD MOVEMENT only. It sounds like it passes just fine!

    Try holding down LINEFEED button instead. :-)



  • Back to Printer/Copier/Fax Repair FAQ Table of Contents.

    Ink-Jet Printers

    HP DeskJet problems

    This of course also applies to other HP printers as well!

    Hewlett Packard has on-line information and documentation at:

    Types of HP ink-jet technology printers

    (From: Paul Grohe (grohe@galaxy.nsc.com).)

    The PaintJet printers are 180 DPI and the DeskJet printers are 300 DPI. The resolution of the PaintJet is about that of a poor 24 pin printer. The PaintJet and ThinkJet printers are also PCL, so you can use a HP laser printer driver set to 150 DPI.

    There seem to be currently four levels of HP ink-jet printers:

    1. ThinkJet/QuietJet: The original. Small see-through bladder cartridges. These are small, compact, quiet, form-feed printers. Text quality was about that of a 9 pin (I still love the little ThinkJet printer; damn near indestructible, small, and built-in Epson emulation). (BTW, look in the 1989 HP Optoelectronics handbook for the datasheet of the miniature ThinkJet cartridge). Original cartridges needed special paper for best printing. Replacement cartridges that print on plain paper are now available.

    2. PaintJet: The first color printers. Cartridges are bigger, 'squarish' and usually are mounted horizontally. Resolution is the same as their 'little brothers', the Thinkjets (180 DPI). There are black, combined color and separate color cartridges (and sizes) available for the different printers. Printers were generally form-feed.

    3. DeskJet/DeskWriter: 300 DPI. BIG improvement. Cartridges mount vertically. Black and combined color cartridges are available. Printers are sheet feed and plain paper printing.

    4. DeskJet 800 series: 600x300 DPI B&W, 300x300 DPI color. Cartridges are tall and narrow and mount vertically. Damn near laser quality w/special paper.

    Dissertation on HP DeskJet repair

    These comments are in response to: "Repair Brief #49 - Part 1: HP DeskJet Professional Printer - Dead" and its followups. My text is indented. See those articles for details. The quick summary is that I picked up this printer at a garage sale and first had to dry it out and repair some cold solder joints before it would print at all.

    (From: Paul Grohe (grohe@galaxy.nsc.com).)

    I've dealt with a few of these buggers before! ;^)

    Is yours a DeskJet, DeskJet Plus, or any of the DeskJet 500 or 600 series?

    If not, then ...well....then I may as well tell you this anyways because you will probably run into these some day....(some of the below can apply to other ink-jet printers).

    Try holding down 'FF' during power-up, you may get a different test page. One of the pages should have a jet-test pattern (A slanted diagonal line separated by 11 vertical marker lines and little jet ID numbers).

    The first page of the standard self test results in that pattern.

    I first tried the cartridge that looks exactly the same as the one that came with the printer (though the part number is different). Then, I tried another somewhat larger one that apparently has identical connections.

    The different part numbers are the 'standard capacity' and the 'high capacity' cartridges. They're interchangeable.

    I assume you have cleaned the contacts (with a Q-tip, on both cartridge and socket). Use a magnifying glass and check *each* of the gold 'bump' contacts. Repeated cartridge swapping, or improper insertion, can cause a crack to form around the base of the 'bump' and the pad (or the pad and the trace). The 'bumps' can also be 'flattened' by cartridges that were forced in at too much of an angle. There should also be some 'give' or 'sponginess' to the contact area to assure even contact with the cartridge.

    Check for broken/bad traces in the flex-cable that goes from the driver board to the cartridge. Ohm out the cable between the supply commons and the individual driver lines (at the PCB) with the cartridge in place. I think the jet resistance was about 50 ohms (It's been a while). There were four separate jet sections (commons). All four commons were tied to the +20V supply through four separate (12 ohm?) series current limiting resistors. The driver outputs seemed to be grounded emitter, open collector (w/clamp diode?). The jets themselves are driven individually and are not multiplexed.

    To test, I printed an all-black page (with an empty, but installed cartridge) and watched for activity on each of the lines at the PCB end. Good pulses are 'bi-levelish'. Normally negative going 20V, with pulses down around 15 V, and going all the way near ground for that particular jet. The commons 'bounce' because of the shared series current limiting resistor, causing the numerous smaller pulses around 15 V (caused by the firing of other jets sharing that common). A bad connection will show up as a weak or distorted pulse. An open or broken line will show up as 0 V. I theorize that a bad driver would show just the smaller 'line bounce' 15 V pulses and a shorted driver would show 'GND' (and also would blow out that jet!).

    The current involved to drive the 'jets' is a pulse of short duration and pretty high current. Any poor connections will cause excessive I/R drop and the jet may not fire hard enough. A sign of this is drops (dribbles) of ink that form on the head during printing.

    While you are in there, check and clean the rectangular rubber seat that the cartridge rests on in the 'parked' position. Dry ink can cake up on it, causing a faulty seal and resulting in dried-up cartridges ($$$!). The rubber seat pulls off and is easily cleaned with a wet paper towel (wear gloves, or you will suffer the dreaded 'black finger syndrome'). Also clean the 'nose wiper' that sticks up about a centimeter to the left of the cartridge seat. This always cakes up and can cause printing problems.

    To manually prime an uncooperative cartridge, you do not have to suck on the business end. You can gently blow into the top vent (located on the top of the cartridge, inside the green arrow) to prime it. But be careful!; If the jets are severely plugged, ink may blow out the check-valve on the bottom (under the plastic 'flap' with the 'maze-like' area). Very messy! Have a towel ready!

    The old DeskJets were (and still are) notorious for paper feed problems as they age. This is caused by the three big paper pick-up rollers drying out and becoming hard and smooth. Roughen them up with some rough sandpaper. The HP FTP site has a article about this in the DeskJet DOC directory. A free kit is available from HP (to qualifying S/N#'s) that 'dresses' the rollers (basically forces the rollers to turn and sandpapers them).

    OH! Biggie! Another big 'failure mode' of the early printers is that the paper sensor lever will jump out of position and jam if the printer has suffered some rough handling (especially if it was turned upside-down or on it's side). The paper sensor lever (pivot) is located on top above the middle roller. The other end breaks the beam of a photosensor. The 'interrupter' end will move over just enough to wedge itself above the photosensor. This is cured by simply raising the lid and wiggling it until it drops back into position (I have 'fixed' many an alleged 'broken' printer this way). The 'interrupter' end seems to have been made larger on the later printers to prevent this.

    From time-to-time, the cartridge's nose should be wiped clean with a soft, moderately damp cloth (~ every 100 pages). Keep the 'business' end pointed down when handling/cleaning the cartridge (Yes, this means hold it above you and clean it from the bottom!). This keeps the galleys and jets primed.

    I concur. If just *one* jet is not firing, then it is on the driver/flex- cable/connector/cartridge side. All the nozzle decoding is done on the driver board, so the 20 pin interconnect cable is okay. The DC (well..really 20VAC) power connector does take some abuse in normal service, this could have aggravated the cold joint.

    Don't forget to check the buttons for water damage/contamination.

    I also have a color PaintJet 300 with a possible "dead" driver line, but I focused my attention to the ailing DJ500, so I did not have a chance to "buzz-out" the PaintJet cartridge. From looking at it, it looks like the PaintJets are multiplexed in some way (there are more jets/contacts than wires in the flex-cable). I never got around to fixing/looking into it (it's still sitting there).

    BTW 1; The DeskJet, DeskJet Plus and DeskJet 500 (non 'C' models) are basically the same (except for some internal fonts). The DeskJets speak PCL, so if a driver for a DeskJet is not available, you can use a basic HP LaserJet driver (but the margins may be cut off, as the DeskJets print area is not as big).

    These things are so damn simple that not much can happen to them. I have yet to run across one with a severe electrical problem. They are always minor mechanical failures (or missing power bricks...$35 from HP).

    All the DeskJet/DeskWriter printers, up to and including the 6X0 series, use the same B&W cartridge as the original DeskJet. Those cartridges will still be available for some time. Your printers life is not over any time soon!

    The DeskJets are good, sturdy and reliable printers (as long as they are well maintained) You did clean the rubber cartridge seat and flap. Right?.

    BTW 2: For maximum cartridge life, make liberal use of the "draft" setting for "not-so-important" printouts (or, er, um, drafts!). It also prints faster because it "swipes" once per line instead of twice.

    BTW 3: Use the cheap 'Shark' brand inkjet paper for best results. Pretty near laser quality! Regular copy paper tends to bleed, but is fine for general use.

    Can you tell I have a 'few' of these printers around???? ;^)

    Is the cartridge full? As you get down to the last 20% or so of the cartridges capacity, it tends to start doing this. I guess there is not enough pressure "from above" to force the ink down. If you can start seeing through the cartridge, you are probably near this point.

    In troubleshooting the printer, you tend to "burn up" cartridges a *lot* faster than in normal use.

    This can be a symptom of the print head not seating firmly when in the "parked" position. Use a dental mirror and make sure the seat presses firmly against the head. One cause of this can be turning off the printer before it has a chance to run through all of it's "housekeeping" cycles at power-up, reset (re-boot), or after printing. During certain parts of the cycle, the head is moved slightly, or the cover is moved. Turning off the printer too soon may leave the head exposed. Always let it finish, then turn it off (warn others about this).

    If you haven't already, just pull the thing apart and give it a good overhaul (get your favorite pair of Torx bits ready!). Clean all the rubber tires, seals and "nose wipers". Wipe off the slider bar to remove any old lubrication. If there was a serious ink leak and the printer was involved in some "circus acrobatics", some of the ink can get on the slider bar and contaminate the factory lubrication, causing it to become "pasty". I wipe the slider bar clean with a cloth then apply a *light* coating of a light, teflon-type machine oil with a cloth (I use "Tri-Flow", a spray-on type usually found in bike shops).

    BTW 4: In the winter months, with it's low humidity, the rollers will shrink even more, causing even more paper feed problems. This is also compounded by the fact that the paper sometimes develops a static charge and tends to "stick" together. Sometimes it pulls two or three sheets in at once, or the paper sticks firmly together in the tray and the weak, dry rollers cannot pull the paper in. Just remove the stack of paper and "fan" it out to loosen it (especially if it has been sitting there unused for a couple of weeks).

    These printers are, like some other things we won't mention, 'Use `em or loose `em'! They work best with frequent use. They do not like sitting around for months unused. Three months seems to be the limit before a 'good' printer will start to dry up from no use.

    I never really investigated the timing of the pulses. I'm not sure how they vary the pulse width. I looked at the pulses when it was doing the first page of the self test, which is mostly text, and all the pulses seemed to be the same width.

    Happy printing!

    HP ThinkJet printer repair 1

    (From: Paul Grohe (grohe@galaxy.nsc.com).)

    The ThinkJet is VERY simple. The ThinkJet printers (and clones) do not employ any type of printhead covers or 'priming stations', so the cartridges are prone to drying out if not used for a while. A quick 'priming' is usually required, even after only a week or two of non-use.

    The cartridges also tend to leak if placed in odd positions or subjected to rapid temperature changes. Make sure the cartridge has not drooled on itself and caused ink to cake down on the contacts in the holder. Clean the gold contacts *gently* with a cotton swab moistened with rubbing alcohol.

    BTW: Like motor oil, fresh ink is great for cleaning up old, dried-up ink.

    The ink is contained in a rubber bladder inside the plastic shell. There is a hole in the 'butt-end' of the cartridge. *Gently* stick a bent paper clip in and push on the bladder to prime it. A drop of ink should form on the printhead. Use a piece of tissue to wipe the drop off and re-install the cartridge.

    Note that there are two types of HP ThinkJet printheads. One is the older, original type meant for printing on special 'ThinkJet' paper, and the newer 'Plain Paper' ones meant for, well, plain paper! ('PLAIN' will be printed on the side of the cartridge).

    The older cartridges printing will appear very light if printed on plain paper. Make sure you have the 'Plain' type. Note that even with a 'plain' paper cartridge, the printing is lighter than a Laserjet or DeskJet, especially in draft or single pass modes. Don't expect razor sharp printouts. This was the first Inkjet printer!

    As for the missing jets, eyeball the cartridge contacts and see if they appear straight and aligned correctly. The contact area could have slipped and may be out of alignment (although rare).

    The flex cable/connector assembly is held in place with a pair of plastic bars. The "bars" have two pins that snap into the 'carriage' (they also provide alignment).

    If the contacts appear to be out of alignment, carefully pull out the plastic bars to release the contact pad, realign the holes and press them back into position. Make sure the rubber 'bumps' behind the contacts are clean and undamaged.

    (This makes more sense when you actually see it :^))

    Be careful! Nothing needs to be forced.

    HP ThinkJet Printer repair 2

    "I have an HP ThinkJet 2225C printer. I just replaced the print cartridge. It still doesn't print dark enough, and even after I primed the cartridge a few times, it still also misses a dot at the top and the second one from the bottom.

    I'm wondering, could the voltage to the cartridge be too low?"

    (From: Kevin).

    I have seen on rare occaisions the cartridge bad out of the box! Try wiping down the cartridge head & contact points on the printer with a Q-tip & alcohol. Sometimes blowing in the vent holes will force ink out the head, wipe off excess and try it. You may have to repeat the procedure a few times. If this doesn't work get another cartridge. You may want to try swopping the bad cartridge into a working unit or taking a working cartridge and putting it in the suspect printer.

    (From: Frank Reid (reid@indiana.edu).)

    I agree with all Kevin said. I use blue window-cleaner (e.g. Windex) instead of alcohol; the ink is very soluble in that stuff, and it penetrates the tiny holes in the printhead. After cleaning, hold a rag over the printhead and sling it downward a few times (as if throwing, but don't let go), such that centrifugal force pushes some ink out. If that doesn't work, try blowing on the upper vent.

    On a few rare occasions I've encountered bad connections at the fixed end of the printhead cable, fixed by reseating the connectors. Also, if the cartridge has leaked, there may be ink on the gold pads in the moving end of the printhead connector, causing bad contact. Clean as above.

    Some of the later models, including the type which takes two cartridges (3-color and black), have screws at the end of the carriage rod which allow adjusting the clearance between printhead and paper. Those may need adjusting if the ink is smearing. If too light, it's probably a printhead problem.

    (From: Richard M. (Digitech@bogus.net).)

    It is a water based ink. There is no need for any solvent other than water. Warm water works well. Use it all the time on my 1200C and DJ750C... BTW, I never have to touch my Epson. Use lint free cloths to tamp dry. NEVER wipe.

    (From: R. Wagner (rwagner@ncn.net).)

    I found the cable from the computer to the print head had some open places close to the head. The want 35 dollars for a new one. I went to the auto parts store and got some a rear window defroster repare kit. I got it working but for how long I dont know.

    HP DeskJet paper feed problems

    (From: John T. Black (cz667@cleveland.Freenet.Edu).)

    The paper feed problem afflicts the HP DeskJet 550C and 560C, DeskJet 520 and DeskWriter 520 printers produced between June 1993 and March 1994. The affected units have serial numbers beginning with 'US3' through 'US43.'

    The problem seems to be that the rubber rollers become slick over time and then the paper doesn't always feed properly. Last year HP offered a free paper-feed cleaning kit to fix the problem. Try contacting HP at 800/656-2324 or 510/657-1473 (FAX) to find out if the free kits are still available.

    (From: Allen E. Amey (a_amey@ix.netcom.com).)

    Try contacting the manufacturer. I have heard that HP has a free kit for the 500 series printers. The kit dresses the rollers and is supposed to be a fix for the type of problem that you are experiencing. BTW, using alcohol can actually compound the problem by prematurely drying out the rollers.

    (From: FaxRepair (faxrepair@aol.com).)

    I believe the only replacement part would be the entire paper pickup assembly which may need to be replaced because the gear train is damaged from ink having dripped onto it. Once the gear train is out of timing there is no known cure. Clean the rollers with rubbing alcohol and a soft cloth. If it doesn't pick up the paper after cleaning the rollers, then remove the entire print assembly and look for signs of ink on the gears at a location directly below the ink cartridge's home position. On a few occasions I have had success by flushing the gear mechanism with warm water to wash away dried ink.

    (From: James E. Burke, Jr. (jeburke@ibm.net).)

    I fixed one for a friend a couple of months ago. Parts are not available (well, you can get them, but they're too expensive).

    In the one I fixed, it was a broken plastic part that caused the misfeeds. To get to the part, I had to disassemble the whole printer.

    If you decide to to this, check the two 'fingers' that are behind the print head when it's in the parked position. The hook on the tip of one of them was broken off. I found the broken part inside the printer and glued it back on with JB Weld (twice--first time backwards). The pair of 'fingers' are identical so you could probably swap parts from one of the other machines instead of attempting the repair of the "fingers".

    (From: Paul Grohe (grohe@galaxy.nsc.com).)

    I have the same problem.

    The rollers dry up and become glazed-over and smooth. You need to 'rough' them up.

    Try sandpapering the wheels with coarse sandpaper (100 to 200 grit).

    You'll need to trick the paper sensor. Take the cover off and lift-up on the black paper sensor lever. Then hold the piece of sandpaper firmly against the wheel and hit 'FF'. You'll need to do this repeatedly, as the wheels will only spin a sheets' worth each time.

    Do this until the wheels feel 'sticky' again.

    It also helps to keep the paper tray full at all times (but not overloaded).

    Unfortunately, they'll never be like new.

    (From: Frank Reid (reid@indiana.edu).)

    I've had very good results cleaning the rollers with naphtha or mineral spirits, no sanding. It removes the glaze from the clay content of the paper, and makes the rollers softer.

    (From: (Egiglious Giggles" (chsoccer@prodigy.net).)

    The thing I have come across, is the spring which is directly under the roller itself. The purpose is to allow tension on the roller for pulling the paper in one sheet at a time. If you look directly in the middle under the roller from the front there is a guide that is spring tensioned. You have to take the roller assembly apart to get to it. But, if cleaning the rollers doesn't do the job, this is probably the culprit.

    (From: Tony Dunlap (tdunlap@odot.dot.ohio.gov).)

    The "Glaze" that gets on the rollers is often due to the rag content of many cheaper papers (especially "Recycled"). To clean the rollers:

    1. Remove the paper and paper tray.

    2. Send a short test page to the printer with the paper out. This will cause the form-feed light to blink.

    3. Wet the rollers one at a time with a cloth (not a paper towel) dipped in alcohol, while pressing the paper feed button.

    4. While it is wet, rub it with something rough and non-porous (I modified a toothed chip extractor that came with a pentium upgrade kit), again while pressing the paper feed.

    5. Wet it again with a fresh part of the cloth dipped in alcohol.

    6. Dry it with a fresh part of the cloth.

    7. Put it back together and let it print the test page.

    Cartridges drying out on early HP DeskJets

    Note that unless the cartridge is almost empty anyhow, it can usually be revived by patting off the caked ink with a damp lint-free cloth and then gently blowing in the vent hole on top until a drop of ink appears at the print head. Sometimes this may have to be done more than once. NEVER poke anything into that vent hole or you will have a mess!

    (From: Paul Weber (webpa@aol.com).)

    HP had a free upgrade kit for the 560 to solve this, maybe for the 500 as well. It was a replacement for the silicone rubber park-position nozzle seal. Also remember that the 500 came with a cartridge storage box with an elaborate rubber seal in the bottom; they encouraged you to remove the cartridge from the printer and put in the box whenever it wasn't in active use to prevent dry-outs. Finally, HP cartridges have expiration dates - and they mean what they say: If they're out dated, they work poorly or not at all.

    HP DJ340 shuts off during printing

    (This may also apply to other battery powered printers.

    "Whenever I send a heavily formatted print job to a DJ340 printer, it prints 1/3 to 1/2 a page and then power shuts off! This so far has happened in TTAX97 and Netscape 4.03. OS is Win95 and I'm using the latest driver for this printer. The printer otherwise prints test pages and simple jobs OK."

    (From: Paul Grohe (grohe@galaxy.nsc.com).)

    I know this sounds silly, but how old are the batteries?

    My guess is that the battery is probably getting weak. Heavy graphic content and "fancy" fonts users (of which TTax and Netscape qualify) will "swipe" the head more per line than the "text and lines" of the test pages. Moving that print head uses a lot of power!

    Does the unit work on the adapter - without the battery? If not, then it relies mainly on the battery for power, and the adapter just charges the battery in between jobs. A weak battery could be drained after a short time.

    If it works without the battery, then the battery could be going bad, causing the charger to dump too much current into the battery and "rob" some of the power from the printer.

    There is a "Troubleshooting" note in the printers "FAQ" on HP's site.

    It basically says to check the batteries and make sure you are using the correct power supply.

    Try replacing the battery. If you bought it at a local store, take it back and see if they have another battery to check it with.

    HP DeskJet 520 - Crunch!

    "I just picked up an HP DeskJet 520 printer that doesn't work. On startup, the print head moves right an inch, then all the way left, where it slams into the left side of the carriage and grinds away for about a tenth of a second before stopping."

    (From: Tech Guy (patrickmcardle@sprintmail.com).)

    You may wish to check the undercarriage (no pun intended).

    The printhead location sensor microswitch may be on the fritz The printer uses this switch to determine the starting point of the printhead after which it uses assumed location by how far the data has sent the head every time the unit gets a reset code, it checks this switch and if the signal is not detected, it may slam the head to either rail end or not move at all. If this is the case you can make sure that the platen is not clogged with label or paper debris. Gently move the head by hand to the right. If you shine a bright light into the area where the printhead usually calls "home" you may be able to see this switch (it may however be located under a cover triggered by the belt) if the switch is defective, replace it. If in fact it is jammed by debris, simply clear it and you may have solved the problem. Beyond this, you may have a logic problem (bad chip or other component) I make a good practice of doing a thorough cleaning of all machines that have left my shop to reduce the possibility of other problems during my warranty period. (it also makes the customer think that they have gotten something for their money)

    I have replace a switch or a fuse on many machines, charged my base fee and heard the response upon their pick-up by customers that, "I can tell right away that you have found and fixed the problem" without even so much as a demo.

    (From: michae98@ix.netcom.com).

    There is a clear plastic strip strung between the both ends of the printhead pathway. This strip of plastic has microscopic vertical bars which the printhead can read and sense what position its in the pathway. The strip may be contaminated with excess ink which may confused the printhead. Take a soft cloth or Q-tip dampened with water and wipe of the strip (the ink is water soluble) and the printer should work.

    (From: Raymond Carlsen (rrcc@u.washington.edu).)

    Closely examine the toothed belt that drives the printhead. Look for a few missing teeth at one end. I managed to make one work again by shifting the belt over a bit (past the bad teeth). If that's it, the belt should of course be replaced.

    HP DeskJet 560C Detailed problem description and possible solutions

    "I have a HP DeskJet 560C, Model C2168A that is behaving badly. When I power it on initially, it appears to run through a diagnostic self-test (as evidenced by the sequence of LEDs on the control panel). It gets to the point where it moves the print head and that is where things go bad. I think it is attempting to report some sort of error code because it then flashes some of the LEDs in a repeating pattern (more on that later).

    First let me describe mechanically what it is doing. When it gets to the point in the power-up routine where it moves the print head, it should do the following:

    1. Move print head to the extreme right.

    2. Prime the print head (???), a stepper motor on the right raises a mechanism to contact the print head.

    3. Position the print head in a ready position.

    OK, here is what it is doing (please forgive my feeble attempts to describe in words what is happening):

    1. I hear three distinct sounds (whirring of various stepper motors I think) before the print head moves.

    2. The first two sounds seem normal from what I can remember when the printer used to work.

    3. The third sound is the loudest and doesn't sound at all normal. It sounds as if the stepper motor that does the priming is oscillating back and forth between two "steps" (the sound is like a stripping gear).

    4. The print head moves approx. 1" to the right.

    5. The print head immediately moves approx. 1.5" to the left (note, this sequence of print head movements happens bang-bang (no delays between movements).

    The end result is that the print head winds up about 0.5" to left of the position it was in when the unit was powered on. If I continue the power on sequences enough times it will end up at the extreme left and will be accompanied by a much uglier, more sinister sound of the print head slapping against the leftmost guard (as if the printer is attempting to throw the print head through the case).

    Now let me describe the sequence that happens with the LEDs. The control panel has 9 LEDs arranged in three columns of three LEDs each. The leftmost column of LEDs lies between the "CLEAN" button at the top and the "Font" button at the bottom. The middle column of LEDs lies between the "Alignment Test" button and the "Status" button. Finally, the rightmost column of LEDs lies between the "Install Print Cartridge" button and the "Quality" button. Here is some ASCII art:

    
                                  CONTROL PANEL
     ===========================================================================
     ||                                                                       ||
     ||                                  Alignment         Install Print      ||
     ||  RESET          CLEAN            Test              Cartridge          ||
     ||                                                                       ||
     ||                 ,--,              ,--,              ,--,              ||
     ||                ( #1 )            ( #4 )            ( #7 ) o o o       ||
     ||                 '--'              '--'              '--'              ||
     ||                                                                       ||
     ||                 ,--,              ,--,              ,--,              ||
     ||                ( #2 )            ( #5 )Busy        ( #8 ) o           ||
     ||                 '--'              '--'              '--'              ||
     ||                                                                       ||
     ||                 ,--,              ,--,              ,--,              ||
     ||                ( #3 )Condensed   ( #6 )Ready       ( #9 )Econo Mode   ||
     ||                 '--'              '--'              '--'              ||
     ||                                                                       ||
     ||  Load/Eject      Font             Status            Quality           ||
     ||  Paper                                                                ||
     ||                                                                       ||
     ===========================================================================
    
    
    I have numbered the LEDs (using my own numbering scheme) so that I can reference them below.

    Here is the sequence that the LEDs progress through each time the unit>is powered on. The sequence is always the same.

          LEDs On       Duration                   Description
        -----------    ----------     --------------------------------------- 
      1. 123456789      2.5 secs       Happens immediately when I switch the
                                       power on.  Then LEDs 234789 turn off.
    
      2. 1   56         0.5 secs       This is a flash (longer than a blink).
                                       Then LED 5 turns off.
    
      3. 1    6         2   secs       Then LED 7 flashes on.
    
      4. 1    67        0.5 secs       This is a flash.  Then LED 7 turns off,
                                       LED 5 blinks on.
    
    **5. 1   56         ----           Here LED 5 just blinks on then off.
    
      6.  234  789                     This starts the alternating sequence
                                       where I believe the printer is trying
                                       to report an error code.
    
      7. 1    6                        This is the rest of the alternating
                                       sequence.  The printer then repeats
                                       these two patterns forever (LEDs 234789,
                                       followed by 16).
    

    ** Step 5 is the point where the printer starts moving the print head."

    (From: Jason D. Pero (JDP6640@ritvax.isc.rit.edu).)

    The grinding sound from priming area is the jammed lever black stick that is pushed towards a bit towards right. If it good, it should be in upright position. If stuck too very right, unstick it by pushing it back to upright position towards left. This stick can be seen between the carriage rod and the printhead's purging rubber nipples and wipers. Also clean (gently!) the clear plastic strip with that fine black lines on it. First the clear strip must be removed first before doing this operation: The sensor is behind the printhead riding the clear strip, remove it by unengaging two triangular fingers inwards from outside and pull the sensor unit outwards towards back. Dust off inside that sensor gap and snap it back in.

    Finally clean and oil both carriage rod and the angled underside area where the bearing block contacts upward onto it. Oil that carriage motor carefully and all stepper motors.

    That should solve everything. This have happened to my 520, and my friends' 540 and 560C. Pretty common problem! Usual action when misbehaving is slamming either stops or do a "rushed start/stop" and some odd scary noises. All complains with pretty, interesting alterating flashes from the LED's on the control panel.

    Pure or almost pure alcohol stuff is best as it does not melt anything or rub marks off and some 2 in 1 heavy duty oil "blue band" can. Top and bottom white shells comes apart easily after unengaging four snaps, doing one at a time and pulling gently and with a small flat screwdriver. Top off, the engine is free. disconnect with care to both ribbon cables one for carriage motor, and the flat white ribbon, or in some models that uses dual printheads, unplug another stepper motor. All connections you need to worry about is only from the mainboard side. Then the print engine lifts out without any fastening hardware.

    WELL DESIGNED 5xx series compared to many printers past and now! I have a 520 chugging away after this fix and real cheap for that printer from a owner who does not want it.

    Only problem is cost of cartridges. :( $50 of two versus $13 can of toner powder for an Okidata 400 that will last thousands of papers. Only problem is Oki. 400 LED laser thinks (processing graphics) very slowly. Is there a hack to swap the proper circuit boards from other similar Oki 400/800 series to make it work faster and more useful than a pokey 186 cpu equipped Oki 400???

    Your comments and suggestions on which brand of refill inks that is perfect for those cartridges. I know how to refill it right after experimenting on a bad cartridge and successfully refilling one good cartridge from a bad cartridge (dead jet out of 48 jets I think).

    (From: Glenn Allen (glenn@manawatu.gen.nz).)

    It is not a stripped gear is it?

    The old DJ500 used to have 2 levers on the right hand side at the back that went up and down. Sometimes these got stuck and noises could be heard. Normal paper feed problems here.

    A problem with a DJ850 was that paper got stuck and to get it out I had to remove the paper feed motor on the drive shaft, when put back it would bang the left hand side of the case. Needles to say it needed the cog setup back to right place it expects when powered on.

    Those printers have an index strip that the printhead follows doesn't it? Is this clean, i.e. Not ink all over the place.?

    Lastly if you are repairing and turning your printer up and down, check you do not lose the rubber cap where the printhead sits, and clears the guns, If you do your cartridges will become clogged in no time.

    Also clean the print head shaft, any gunk on it will cause the printhead head to stick thus giving error light or worst powers down the printer.

    Cartridge detection on HP DeskJets

    (From: Fred Keen (fkeen@repeatotype.com).)

    The HP printers test for the presence of a cartridge by checking the electrical voltages on the contacts between the cartridge and the cable. The slightest amount of dirt on the contacts can give a false reading making the printer think that no cartridge is present. If cleaning the contacts does not work you will have to buy a new cartridge.

    HP Deskwriter 660 printer problems

    "My HP Deskwriter is just over the warranty of one year and when I print text instead of white lines through the type which would indicate to clean cartridges or replace them, I get black thin lines almost smearing slightly the text."

    (From: Dennis Bathory-Kitsz (bathory@maltedmedia.com).)

    1. Take out the cartridges and clean their sides, which pick up hair.

    2. Clean the cartridge-cleaning mechanism itself on the right, especially the foam pad.

    3. Take out the cartridges and clean the bottom of their carriers.

    For this last, there may be some diagrams accessible via the HP Support Page.

    Little plastic parts in HP DeskJet printers and HP service policies

    (From: Wayne Van Beelen (wbvanb@nbnet.nb.ca).)

    The bad news is that the plastic these parts are made of seem to be a Teflon hybrid and even the best epoxy doesn't last real well.

    The even worse news is that DeskJets are disposable, just like Bic lighters.

    HP will NOT sell you any internal parts.

    They will not sell them to your dealer.

    They will not even sell then to a so called HP service center.

    All DeskJet service takes place in Corvallis, Oregon. A second possible location is Mississauga, Ontario but I think they just forward printers to Corvallis.

    Here's the deal as I've been told; you pack up your printer and courier it to Mississauga, ($40 Cdn.), pay $175 Cdn. for a refurbished version of your Deskjet, and then pay another $40 Cdn. to ship the refurb back to you. That's $255 Cdn for a used printer when there are any number of new printers that can be had for a comparable price (and would also have a warranty).

    That, to me, means DeskJets must be disposable because nobody in their right mind would pay that much for a three or four year old printer. It's bad enough when you consider 540's, which back then had a 3 year warranty, think about all the poor suckers buying newer HP's with only a 1 year warranty...

    That's got to be enough harping on my part, the short of it would be that if you've got it working and your cartridge parks okay, it might be best to leave it alone. You won't get any worthwhile out-of-warranty help from HP. Check on parts availability on any future new printers you might ever buy. You can't assume that they won't forget you the day your warranty expires.

    HP DeskJet 500 repair notes

    (From: kmlee (kmlee@email.com).)

    For a printer made in 1992, it can sure last a long time. I must have opened it up about 20 times though.

    The most serious problem happened recently when the printer switch was turned on. The LEDs would flash, and the printer would go off. A quick search on the Net confirms (albeit a 1200C) that it was some kind of power supply protection thing. Opening up the print, to my horror, I saw a familiar oily look around the power supply PCB. Capacitor leakage-again! The Nichicon 1,800 uF as well as the 2,700 uF had the oily acid seeping from it and some of the components had green and/or rust on it. First thing - remove the PCB and washed it under running water, using a toothbrush to remove all acid and flakes of solder resist from the solder side. Some copper tracks had completely been eaten through. Others had dark spots underneath the green solder resist. I removed them as much as I could, knowing that these would be the source of future corrosion.

    I soldered back those points which were meant to be connected and used insulating varnish on the exposed copper. I got suitable capacitor replacements. Before connecting back and powering up, I measured the voltages just to make sure all's OK

        Pins:    1      2      3      4      5      6      7     8      9
       Volts:    0   21.2      0    19.76   0.17 -10.56  10.7   5.27  26.8
    

    (Voltages were confirmed to be correct by checking on the Gnd/Vcc and other pins of chips with known part numbers on the mainboard.)

    Good repairing!

    HP DeskJet 560C - stripping gear sounds and more

    "Does anyone know where the problem might lie with my HP printer? The problem is that when it is turned on, it goes through the reset sequence until it reaches the park zone, then it seems to miss a gear or something by the sound of stripping gears, then the lights flash alternately. My workaround to this is to turn it on, let it start across on it's reset sequence, turn it off, then right back on, and it will initiate just fine. Another anomoly is that when printing large color graphic files, occasionally, it will make it part way through the page and just stop with the same flashing error. After resetting it, it of course will print garbage unless I resend the data to the printer all over again. Any ideas? I've left a message on the HP site, but there has been no response."

    Call HP - After much hassle they finally admitted it was a defect and replaced it with a new 600 series. I had the same problem - but had to call Idaho to get results.

    HP600C DeskJet produces too much black ink

    In addition to cleaning the cartridge, replacing the cartridge, cleaning the ink "well" and rubber wiper used for wiping cartridge head, using "approved" paper, printing in econofast mode (less ink), and setting up "transparency" print mode (gives more time for drying), one thing is often overlooked:

    (From: Ralph Wade Phillips (ralphp@techie.com).)

    Did you also clean the cartridge HOLDER? See HP's web page for more details, but I've seen SEVERAL of the 600 family that have "dust" collected under the cartridge holder. Since the black hits at a different angle than the tricolor cartridge, it is more prone to hitting the dust buildup, causing excessive smearing.

    BTW, beware of flipping the entire printer over to unlatch the top - you may get a shower of the last n years excess ink from the holding tank!

    HP DJ power supplies/wall adapters

    It seems that this is one part that HP may not totally gouge you on!

    (From: Paul Grohe (grohe@galaxy.nsc.com).)

    Go to this page below, scroll down to the "power module options" section, and pick the correct adapter part number for the UK.

    Then do a net search for that part number, or, contact HP directly. Last time we ordered some, they were about $35US from HP.

    HP 600 series DeskJet printer smears even with new cartridge

    (From: Bill Rothanburg (william.rothanburg@worldnet.att.net).)

    I had a similar problem with a HP 693C. The problem was the spacing between the paper and the carriage. A suggestion: if you're not mechanically adept, don't tackle this, get someone who works on printers to lend a hand.

    I have not taken my 600C apart, and will not do so unless it fails, so the following information is based on the 693C, a similar printer.

    The top cover is held in place by some latches, and a couple of screws under the paper tray. Be careful while tipping the printer, there is a catch-basin for the ink, and if this spills you will have ink dripping inside the printer. Remove the upper cover. Be careful with the thin cable to the electronics board. At this point you should be able to check for any gobs of ink that have turned to paste. Clean the dried ink off of everything, especially the bottom of the carriage, and print a test page. If it still smears, it's time to try adjusting the carriage height.

    On the 693C the carriage slides on a rod that runs the width of the printer. The anchors consist of a screw through a slotted hole. On the one I fixed, the screws had obviously been loosened (they're torx screws, and it was obvious that something such as a jeweler's screwdriver had been used on them). Anyway, loosen the screw at one end, lift the rod slightly, and retighten. Print a test page, and repeat if it still smears. Of course, if it now smears only at the other end, it's time to switch ends.

    I'm sure at the factory they use a gauge to adjust this to within a micron but the empirical approach worked for me.

    HP DeskJet 692C - Random lockups

    (From: Jess Askey (jess@magenta.com).)

    I did a search when BOTH of my HP692C DeskJet printers started getting flaky. I didn't find much except for a post mentioning that cleaning the small plastic 'barcode' may solve most problems. While this is exactly what HP customer service suggested as well, it didn't solve my problems.

    What the printers were doing, were randomly locking up. They also started making a 'knock' sound while they were printing. But, the 'knock' sound was more prevalent than the actual 'locking up' problems. But they would still lock up more than twice a day.

    What I found was happening was that the stepper motor belt was skipping a tooth when the print head was changing directions. There is a black plastic tensioner arm on the left side of the printer that holds the belt tight and this was getting yanked in enough to let the stepper belt have some slack.

    What I did to fix this was to take the spring out from behind the black tensioner arm and stretch it out to put more tension onto the stepper motor belt.

    Both of these printers have had heavy use, they both are just over 1 year old right now too. I only moderately stretched the first spring and it still made the 'clicking' noise every so often. On the second one, I probably stretched it about 1/2" to 3/4" in it's fully relaxed position, but I think when putting it back into place it probably bent back a small amount. This worked well, the belt did not feel overly tight and I have not had ANY problems whatsoever. :-)

    HP 820Cxi DeskJet Problems

    (From: Vic Zane (vic@webworks2000.net).)

    I've been having a problem with the black cartridge in my HP 820Cxi printer getting all gummed up with ink on the bottom, making lousy print. Clean it off, and it comes right back. It also was missing a horizontal line or two - thin but noticeable. The "clean" instructions with HP troubleshooting didn't help at all. Interesting that they say there is another thing you can try, but don't do it except with NEW ink cartridges! At $30 or so each, I wasn't interested in trying that except as a last resort.

    The other day, after cleaning and refilling, I got an error message telling me that my black cartridge was no longer usable, and that continued use would possibly damage the printer. I purchased a new cartridge, and replaced. The old cartridge again had the buildup of ink on the bottom. So now I got the same "unusable" message, with recommendation that the cartridge be returned for replacement. And again, the bottom was loaded with ink. Obviously this was not just leakage from a faulty cartridge.

    Information found on the web indicated that HP has only one repair location, and will not sell repair parts to even their dealers. Probable repair costs, added to shipping two ways, lead me to believe that I would be money ahead by either repairing it myself, or junking the printer. It has been in service (I am a retiree using it at home) for just over three years.

    There should be information on this printer accessible on-line which is not included with their on-screen maintenance information:

    I also referred to this document at a Sci.Electronics.Repair FAQ site.

    I removed the cartridges, and stood them upright on a multi-thickness pad of paper towel that was moistened with distilled water (from dehumidifier), figuring that this might open any ink jets with dried ink in them. A flashlight helped to see the area at the far right of the printer, where the cartridges park. Those wipers were a real mess. The Q-tip swab technique proved quite unhandy, but with a larger wad of cotton on the tip of a long and narrow needle nose pliers, I was able to clean them. There is a well to the left of the wipers that appears to have a spongy material in it - well soaked with black ink. When I tried to clean it, it just depressed down into the well and stayed that way. The pads that rest against the cartridge bottoms when in the park position were inaccessible, as they retract when the carrier moves away.

    The paper toweling soaked up a little ink (I had some plastic under it). I wiped the cartridge bottoms, then replaced them in the printer. Alignment worked well - no skips or smudges. But I kept getting the error message telling me to cancel printing and align whenever I started printing, until the computer had been shut down and restarted.

    The printouts are now first class, and there are no more error messages. The "unusable" cartridges both work fine. Of course it has only been one day so far though!

    (From: Someone who wishes to remain anonymous.)

    I can only add that the cover comes off quite nicely by unscrewing the two screws found on the top of the printer toward the back and by wedging back with wads of folded paper the four plastic clips on the printer's bottom. With the cover off you have good access to the area that needs cleaning. Also, I used rubbing alcohol rather than water. The ink well is just that. There is no spongy material there. Mine was just full of waxy ink that had accumulated there over time. Needless to say, I dug that all out. Hopefully the printer should work well for another two or three years.

    HP DeskJet 1200C power supply repair story

    (From: Marc Geyskens mgeysken@innet.be).)

    A while back, I got this broken down printer, most of the time the power supply wouldn't kick in after pressing the standby switch. After checking elementary things, I got stuck on the PCB that holds the standby switch, on it reside passive components, a few LM431 and a UN3854 all of the components where ok except for the LM and UN chips. Since I had no schematic and no sheet on the UN3854 I turned to the chip directory which led, via a few stops, to the Unitrode site and yes, a data sheet for the UN3851. Plugged my scope (power supply on isolation transformer) onto the ucc line for the UNxxxx, noticed that the voltage was almost 0 raising slowly to 12 V and then fast to 20V after that time the PS worked normal. So I traced the supply back to a FET 2SK537 on the power supply mainboard which is part of a protection, its gate pulled up by a zener ZD1 and a resistor of 680k from 400V and pulled down by a transistor in case of the transformer's output voltage gets to high. Well, it was the 680k resistor, infinitive resistance yet not a scratch on it.

    Thanks to the Chipdir site, and the Unitrode people.

    HP PaintJet problems

    "My HP PaintJet printer has a problem! When I turn the printer on, the print head moves as if it's cleaning the head but thats it! The "on" light stays on but the "SET TOF", "LF", and "FF" buttons don't work. I've tried a test page by holding down the "FF" button and turning on the printer but it won't print. It just goes through the head cleaning stage again and then stops. If I turn the printer off and manually move the print head to the other end of the carriage and then turn it back on again the print head will move back to it's home position."

    (Responses from: Paul Grohe (grohe@galaxy.nsc.com))

    I am assuming you have the original tractor-feed "PaintJet", and not the sheet-feed 300XL.

    It sounds like you have a problem with the "paper out" detector.

    Is the second lamp on, even when there is paper loaded?

    Here's a clue: If the other light is *on* after you do the self-test key sequence, then it thinks there is no paper loaded, so it does not print. The buttons are useless at this point, too. I have confirmed this with my PaintJet by removing the paper, and it does exactly what you describe. During normal "self test" printing, the paper out lamp is off.

    It is very common with DeskJets and PaintJets to have their "paper out" detectors jam after rough handling.

    Looking down into where the paper goes in, there is a little black lever sticking up (about 8cm to the right of the left end of the platen). This is the paper detect lever. The other end is a "flap" that goes between a photodetector.

    Make sure this lever moves freely.

    Open up the case (don't worry, it is very simple). Pull the big platen knob off. Then there are two rubber "wedges" stuck in two oval-ish latch holes on the bottom under the front "lip". Pull out the wedges and squeeze the latches. The cover then lifts right off (nothing is connected to it).

    With the cover removed and viewing the printer from the front, look at the bottom left corner of the circuit board. You can see the "flap" end of the paper detect lever and photosensor, right above the "made in USA" sticker. Make sure it moves freely and that it is situated between the two detector "blocks" (I have seen these levers "wedge" themselves against the outside edge of the detector).

    My guess is that you will either find paper jamming the lever, the lever itself mechanically jammed, or a piece of paper wedged in the sensor.

    While you have the top off, notice that there is a long, plastic strip with fine lines on it running along the front. This is used for sensing the head position. Move the head over and make sure that strip is clean and that no ink has spilled anywhere on it. Also clean out any paper dust or spilled ink.

    Don't be afraid to plug in the printer to test it with the cover off. The input voltage is only 20VAC, so you will not get shocked. Just be careful of the orientation of the power plug and watch out for the moving parts.

    BTW1: The PaintJet printer is very stupid. It will 'print even with the cartridges removed or the platen motor unplugged, so there are no other sensors that could be causing a problem.

    "The symptoms are that first the color cartridge got weak and stopped working and now the same has happened to the black cartridge. It's not out of ink or clogged and the contacts are all clean."

    The 3630 (aka: "PaintJet") was one of, if not *the* first, color ink jet printer. As such, it was plagued by the usual "first-of-it's-kind" problems. HP learned from their mistakes on this one!

    We have a few of them around here, and your experience is not unusual. They tend to "dry up" more often than the newer printers. I seriously doubt it is an electrical failure.

    Even though the cartridge appears "full", the ink gallies will clog if not used after a certain amount of time. After a week or two, you will need to clean and prime the cartridges.

    This printer does not have the automatic "priming" that the DeskJets have. Instead, you have to remove the cartridges and manually prime them with the "plunger" located under the "flap" on the top-left. Then "wipe" them with the rubber "nose-wiper" located on the underside of the cartridge access door.

    There is (supposed to be) a slide-out card located on the bottom of the printer with the "cleaning and priming" instructions (The little tab with the "i" on it).

    The PaintJet also lacks a rubber-sealed "cover" for the cartridge head when it is in the "park" position. This greatly adds to the "dry-out" problem.

    The head connector also creates some problems. The 3930 uses two rows of individual long, gold-plated "fingers" to make contact with the cartridge. These "contacts" can bend back, or become mis-aligned, due to improper cartridge insertion or wear.

    Take a look at these "fingers", and just make sure they are even and straight. Don't bend them too much, as they are brittle. Also make sure there is no leftover ink on the contacts. Don't press

    It should be easy to fix. However, you may go bankrupt replacing the cartridges.

    There are ink "refill" kits available, however, the problem is usually with the clogging of the internal passageways and jets. So new ink won't help much.

    My suggestions:

    Check the contact "fingers".

    Try "priming" and "cleaning" the cartridges.

    Try replacing the cartridges with known good ones (or new).

    If you will not be using the cartridges for a while, remove them and place them in a sealed container or baggie for storage (place them in the same position as they are in the printer).

    "What other printers are compatible with the PaintJet if I cannot get mine working and I need to use existing software"?

    The "PaintJet" is a 180 DPI, "PCL" language printer. Just like the "newer" DeskJets.

    If your unit has a parallel or serial interface, you can use any one of the older DeskJet printers (500/600 "C" series, DJ plus) - any that use the "PCL" language) or almost any laser printer (HPII compatible - B&W only). However, the newer printers are 300DPI printers, so the printouts will be 30-40% smaller.

    If it is a HPIB interface, look for a HPIB ThinkJet.

    Unclogging non-HP inkjet printers

    These printers have the printhead separate from the ink supply.

    (From: John Hudak (jhudak@sei.cmu.edu).)

    Here are a few suggestions:

  • Do a Google search on inkjet printer repair. You should find companies that make 'cleaner cartridges' that replace the ink cartridges. Invoke the clean cycle on the printer with the cleaning cartridges (follow both the printer manufacturer and the cleaning cartridge manufacturer instructions. This should remove the blockage. You may have to cycle it many times and/or let it sit overnight and then do cycles in the morning.

  • Some companies also sell a syringe kit in which you fill a syringe with cleaner and flush out the print head. In my opinion, this is the best approach.

  • Buy a HP in which the print head is integral to the ink cartridge. This eliminates the problem, and a side benefit is that the print quality is always good.

    (From: Richard J. Scott (rjscott@telus.net).)

    I have a Cannon BJC400 inkjet printer which I only use when I get home every week or so. Of course the ink clogs up the cartridge as always.

    In my frustration, when I couldn't even blow the ink through this time, I took about 4 ounces of windshield washer fluid added about 1 ounce of isopropyl alcohol got it near boiling in the microwave and set the cartridge into it for about 1 hour. Bingo it came clean on blowing through the breather hole and printed beautifully. Nice cheap fix!!!

    Intermittent light/no print from Canon BJ330

    "I have a canon BJ330 that starts printing light and prints nothing. This only happens approx once every 2 months. The unit has ink and it still thinks it's printing but there is no ink on the paper. This has happened a couple of times and so far I haven't figured out what it is that I do to 'correct' the problem.

    I was thinking that there must be a way to clean the printhead that is not in the service manual. Which I do not have, anyway."

    On my DeskJet, I just blow gently into the vent hole on the ink cartridge. I then wipe off blob of ink that forms on on the head and it works like a charm - if you don't get ink all over everything. Perhaps, try the following first:

    (From: russrite@magmacom.com).

    Remove the sponge from the purge cap carefully, try washing in water carefully, and reinstall it:

    Canon BubbleJet information

    Parts Now! has a set of articles mostly on laser printer engines, but there is one for Canon BubbleJets. These can be found at:

    Cleaning Canon BubbleJet printheads

    (From: William Harris.)

    Cannon printers using a printhead often get clogged. The Cannon solution is to clean using the cleaning or deep cleaning selection. If the cleaning does not do the job, you will use a lot of ink in the deep cleaning cycle and it still may not work. The clogged print head can usually be cleaned with a jet of air. I found the best way to do this is with a plastic syringe with the needle insert drilled out. This leaves the outer circular part of the syringe that fits nicely around the raised ink receptors. Then just inject some air through the clogged nozzle. If there is dried ink inside, you may want to add a drop of special solvent for the ink which can be purchased where you buy replacement ink. I like the clear ink cartridges so you can see how full they are. I drill a small hole about one half inch from the top on a clear side, cover the bottom hole, fill the cartridge and put a piece of clear plastic tape over the hole. Then remove the bottom cover and insert. William E.

    Canon BubbleJet printers not printing after cleaning

    (From: Handy (handy@redshift.com).)

    Take out the cartridge that you want cleaned. Find that hole that ink comes out of, squeeze the cartridge until ink comes out of that hole - actually drips. Put it back in the machine, clean it at least FOUR times. Usually on the fourth time for some reason, it works. Just clean the one that you think needs cleaning.

    Canon BJC 600 problems

    (From: Rob Connelly (connelly@ix.netcom.com).)

    I have found that sometimes the BJC 600 series gets confused and needs to be reinitialized. If you haven't already done so, unplug it from the wall, wait 60 seconds for the internal supply capacitors to completely discharge, then plug it back in and try again. When you remove it from the AC line it goes through a complete warm up cycle and resets itself.

    Also, the contacts that mate with the print head are notorious for oxidizing. You might want to carefully clean them (lightly) with a pencil eraser and some isopropyl.

    If these remedies don't work, the Canon 1-800 number will put you in touch with their tech department, and they are really quite good at determining what the problem is over the phone.

    (From: Al Savage (asavage@iname.com).)

    When I was working on printers, we'd see a few of the 600s in with corrosion on the ribbon cable end under the printhead. NewKote apparently had a venting problem with their copykat ink cartridges, where in some situations ink would spurt (leak? drip?) and somehow corrode the ribbon cable.

    I never tried to replace one and see if it could actually be repaired with just the cable, but I did try vigorously cleaning the cable end: no conclusive repair.

    BJC 600 print head error - lights flashing

    "Upon powering up the printer the two lights flash indicating a print head error. However by cleaning the electrical contacts (with alcohol) on both the print head and the printer the printer works,,, temporarily. Within a day or two the problem resurfaces. When the printer does print it prints excellent quality. The nozzles seem to be is good working order."

    (From: Al Savage (asavage@iname.com).)

    Although printhead failures are common on the 600 series, so is failure of the ribbon cable to the printhead. This is an acknowledged problem from Canon, when aftermarket ink reservoirs are used (i.e. Pirana or NewKote). Somehow the ink gets up to the cable/printhead interface and corrodes it. When I was working on them (about 18 months ago) Canon and NewKote were pointing fingers at each other. It appeared to be a reservoir venting problem.

    Epson Stylus Color IIS error light problems

    "The error light on the Epson Stylus color IIs keeps blinking. The color cartridge is new. The black and white prints perfect."

    (From: Robert J. Brancatelli (bronco@mkol2.dseg.ti.com).)

    Most likely, the new color cartridge is not seating all the way. Move the print head to where you normally do to swap the heads. Now, without removing the color print head, lift the most forward lever up as far as it will go, then bring it down to reseat the ink cartridge.

    Cleaning Epson inkjet print heads

    (From: Mike Harrison

    The symptom is missing horizontal lines through text or graphics -- or no print at all. This occurs when the water based inks dry at the print heads in amounts that the head cleaning routine cannot dislodge.

    The newer Epson Stylus Color series print heads are particularly affected.

    It can happen whether you refill your inkjet cartridges or not.

    One contributing factor is turning off the printer from a power bar. This prevents a complete shutdown and docking of the heads at their docking stations. You will notice some activity even after turning the printer off by its switch, as it continues to take a trickle charge.

    To unclog the heads:

    1. Run 3 cleaning cycles from the Epson Utility.

    2. Turn off printer, and restart in Test Print mode.

    3. When cartridges/ print heads are at extreme left of carriage, quickly spray 3 shots of Windex or Ammonia onto docking station(s) affected, and turn off printer for 5 minutes.

    4. Repeat process as needed until perfect test prints are restored - usually 2 procedures.

    We've saved 14 printers this way.

    Cleaning totally clogged colour head in Epson Stylus Color 500

    (From: Colin Guillas (rguillas@nrn1.nrcan.gc.ca).)

    I have an Epson Stylus Colour II printer which had similar problems- this time, which the magenta head.

    After running about 50 cleaning cycles, and having no improvement, I disassembled the unit (I am WAY out of warranty already ;-) and manually mopped out the cleaning apparatus- the rubber heads were VERY gummed up, so I wipe them off... the suction tubes were clogged, so I squeezed them out, the sponges were full, so I mopped them up with a kleenex. I then put on a pair of elbow length kleenex gloves, and pulled the cotton cleaning tray/absorbent reservoir out of the base of the unit, and rung it out into the toilet. There was a three year accumulation of wasted ink in there- this printer gets extremely heavy use, but it was amazing at the amount of ink that gets wasted, compared to what goes on paper! I would guess that it's about 30/70, 70% ending up on paper. Incredible wastage. I just don't buy cheap refills. I buy better ones with guarantees on them. I also replace the cartridges that I am refilling every four to six refills. There will be an accumulation of 'junk' if you don't.

    The cure to my problem? Pay the price for the genuine epson cartridge and do another fifty cleaning cycles. It worked for me. I had to wring out that @#$%liner again....

    (BTW, If anyone else has an epson inkjet, I recommend that they get the liner replaced or at least wrung out. It's a horrible mess which can overflow if you use an awful lot of ink... mine was saturated... you may have a nasty surprise next time you decide to move the printer- all down the front of your shirt. ;-)

    Epson Stylus 800 print quality

    "I have an Epson Stylus 800 printer which is only used infrequently. I seem to have a problem with some of the jets clogging up after a while producing a banding effect and/or a blurring of text.

    The built in cleaning cycle does not clear the problem. Running the head over a pad soaked in Isopropyl Alcohol clears the problem, but after a week or so things start getting bad again.

    The user manual does not mention the need to change any cleaning pads. How does the cleaning cycle work and are there any checks or adjustments which might improve things?"

    (From: Paul Grohe (grohe@galaxy.nsc.com).)

    Inkjet printers do not like 'infrequent' use. They need to be 'exercised' every once and a while. Use 'em or loose 'em!

    I'm not familiar with the Epson products, but on the HP DeskJets, there is a little rubber "seat" that the cartridge sits on when it is 'parked'. If it is gummed-up or damaged, it can cause the cartridge to slowly dry out.

    The HP's have a little oval-shaped rubber 'do-hikey' that seals the area around the ink jets. It generally gets gummed up with dry ink, and does not seal completely anymore.

    Check and see if there is something similar that covers the print head when it is not in use.

    The "banding" can also occur as the cartridge starts getting towards the end of it's life. Also try cleaning the contact areas with a soft cloth. Poor contacts can cause similar problems.

    If large ink droplets are forming on the head during printing, this is a sign of poor contacts or a physically damaged head.

    However, most of the time it is caused by "clots" in the areas supplying the jets, or in the jets themselves. Sometimes soaking the jets in a tray of alcohol or water for a while can dissolve these "clots", but the success rate is not that great. Better to fix the root of the problem.

    BTW: Avoid turning the cartridge upside-down. Always hold it so gravity pulls the ink down to the jets and keeps them primed. Turning it upside-down can allow air to be drawn back into the jets.

    Then again, it may be time for a new cartridge!

    Epson Stylus Color 800 printer seems to operate but no printing

    (From: Al Savage (asavage@iname.com).)

    Sorry to be the bearer of bad news, but the both the purge pump and the printhead in the Stylus series (300, 400, 800, ColorII) are very trouble prone. I've scrapped a couple dozen of them. The cost of a replacement printhead is more than the printer on sale.

    They do print nicely when they're working, though. My experience is that they don't work for very long.

    Epson Stylus Color 800 clogged print head

    (From: Alan G. Pope (agpope@phonetech.com).)

    PROBLEM: Dryed black ink clog-up in the tube leading from the black ink cartridge to the print head. Black ink flow totally halted. New cartridges won't work.

    BACKGROUND: Epson uses very fast-drying, water-soluble, inks in this printer, and if the printer sits idle for some length of time the ink feed tubes and the print heads become clogged with dry ink. Epson issues dire warnings about potential damage to the printer if attempts are made to flush these parts with any solvent, and recommends factory repair only.

    On the advice of someone who has vast experience with such problems, I successfully used the following repair. procedure.

    REPAIR PROCEDURE: Use a clean small hypodermic syringe with NO needle. Press on to the syringe nozzle, a 3/4 inch long piece of model airplane gas engine fuel tubing. This tubing is available cheaply from your local model hobby shop. It is a pale light blue colored plastic tubing. The MEDIUM size is the right one. The bore (ID) of the tubing is less than 1/16 of an inch. It makes a very tight fit when pushed onto the syringe nozzle.

    Remove the cartridge from the printer, and pull the power plug immediately to prevent any further printer movement.

    Load the syringe with 2-3 CC's of scalding hot water, preferably distilled water available at your grocery store. Then press the other end of the tubing down over the little black nozzle in the bottom of the cartridge holder. It must be a very tight fit.

    Forcibly inject the hot water into the printer. If the clogging is really severe, you may have to press the syringe plunger very hard. Continue injecting until the syringe is empty, while making sure that the tubing does not slip off the syringe or the printer nozzle. Repeat this injection procedure 1-2 more times with more hot water if necessary.

    Once the hot water goes through easily, the clog has been dissolved. It may be necessary to wait 24 hours for the water to evaporate, but in my case it was not. I simply replaced the black ink cartridge, and ran the Epson's head-cleaning utility several times until the black ink started coming through. Running the nozzle-check utility, to make a test pattern print, will let you know when the ink flow is OK.

    This same procedure should work equally well for the colored inks of this printer. I suspect that the procedure will also probably work for some other Epson inkjet printers as well.

    Use this procedure at your own risk. All I can tell you is that it worked beautifully for me. There was NO printer damage.

    Non-use and refill of BJC-620 ink cartridges

    (From: Roy (royf@iname.com).)

    The people who talk about clogging, etc. must have never seen a BJC-620, in which the printhead and ink tanks are separate. I've had a 620 for about 16 months and having printed almost nothing on it (have a laser for most needs) have noticed that the ink tanks last about 5 months. My third set of cartridges at $40 per set have just recently gone dry. (Actually only the color ones are dry. The larger black one lasts longer.) I foolishly threw away the first set of empties, but I still have two sets. I decided that I've sent enough money to Canon and searched the web for a more economical solution. What I found was Bob Nedved and his re.ink.kit refill kit at:

  • Re Ink Kit Home Page.

    where, for $74.50 I got an amount of bulk ink equivalent to about $800 worth of new cartridges. Included also are 4 syringes and 4 small screws. The procedure is to make a small hole in each tank tank and seal it with a screw. To refill, you remove the screw, inject a few cc of ink, replace the screw, and clean the syringe with a little alcohol or distilled water. Filling the first cartridge was a little messy, but once you get the hang of it, it's a snap. The kit doesn't completely eliminate buying new tanks, because the tanks themselves eventually need to be replaced, but it sure does cut the annual maintenance cost, whether you only use the printer a little or if you use it a lot.

    (From: Bill Sloman (sloman@sci.kun.nl).)

    Epson uses a piezo-electric print head, and an alcohol-based ink. If you don't like paying for Epson's ink cartridges, use Pelikan's (I think that is the brand I use - it is certainly one of the old-fashioned ink manufacturers). They seem to use a higher molecular weight alcohol than Epson, so the cartridges last me more like six months than three in the old (1993) Epson Stylus Q800.

    HP and Canon use a water-based ink, that is actually heated to boiling in the print-head to spit out droplets - so the print head corrodes rapidly, which is why their "ink cartridges" contain an new print-head and only about 15 ml ink, as much as the print-head can reliably spit out.

    Inkjet Printer Cartridge Type and Reliability

    Here are a couple of opinions. (From: Al Savage (asavage@iname.com).)

    Having worked at Epson, Canon, and HP warranty service centers, I tell anyone who asks me for advice about buying an ink jet printer to always choose one where getting more ink also gets you a fresh printhead. The number one service problem with all inkjets is printhead clogging failures. On the Stylus 800 series, for example, the printhead retail cost was $170, and the labor was about half an hour. On the Canon BJC-600, the P/H cost was $250, but the head could be changed by the owner. And with so many folks using third party ink that works like it was brewed up in someone's bathtub (NuKote, Piranha (sp?), etc.), printhead failures scrapped more inkjets than any other three causes combined.

    Cheap, owner-replaceable printheads help keep cheap inkjet printers out of the landfill.

    (From: Roger Hamlett (roger@ttelmah.demon.co.uk).)

    I disagree with the comments about chosing one where getting ink gets you a printhead. I have a bin full of 'dead' HP cartridges, that have resisted various attempts to get them printing again, yet also have an Epson here, that is four years old, and has never given any problems. The bill for cartridges on the HP, (allowing for the part use), would have paid to replace the printer a couple of times over.

    Ink cartridge expiration dates

    (From: Paul Weber (webpa@aol.com).)

    One other thing about HP inkjet printers (DJ 550, 560, 850): Before you buy an ink cartridge, look at the expiration date on the box. Don't buy it unless you expect to use it before the printed date. That number really means that the cartridge will NOT work after the date...no matter how it is stored. Water and/or hot water rejuvenation rarely works on cartridges that are outdated. The reservoir evidently turns to crap and won't wick the water in or the ink out.

    Dead Cannon, Compaq, HP, and similar power supplies

    Apparently, these power supplies may blow their internal fuse either as a result of an overload, or possibly for no reason at all. In this case, a new fuse will be all that is needed. Of course, it's also possible that there is a fault in the power supply or in the printer which will cause the new fuse to blow but it's worth trying a new fuse before more complex troubleshooting.

    (From: Jim Steel (procomputer@telisphere.com).)

    Repair instructions.

    The power supply is encased in a bonded 2-piece ABS plastic housing. There is a fuse inside but no way to access the fuse without splitting the case.

    Splitting the case:

    Unplug the power supply and secure the power supply in a utility vice. Use a short-blade utility knife or linoleum knife to slowly and carefully and cut along the seam where the 2 halves of the power supply are joined. Don't try to cut the seam all at once. Work a little at a time until the case halves can be separated.

    Replacing the fuse:

    On a power supply with an unsoldered fuse socket, simply replace the fuse and test the power supply. Alternately, a leaded fuse may be soldered in.

    On a power supply with the fuse soldered into the fuse socket, leave the fuse in the socket and solder in a leaded fuse. (A leaded fuse has lead wires extending from each end of the fuse.)

    On a power supply with a leaded fuse, unsolder the old fuse solder in a new leaded fuse.

    Testing the power supply:

    Ensure that the power supply and printer work before bothering to close the case.

    Closing the case:

    ABS plastic cement may be used to bond the power supply case halves. Alternately, electrical tape may be used to hold the case halves together.



  • Back to Printer/Copier/Fax Repair FAQ Table of Contents.

    Laser Printers

    Note: also see the chapter on Photocopiers as the operation and problems of the two types of equipment are very similar.

    On-line laser printer resources

    Warnings about vacuuming laser printer toner

    This is less likely to be something you would do in a big way with a laser printer compared to an office copier but if you are contemplating it, see the section: Warnings about vacuuming copier toner. There are several considerations including the risk of explosion and/or fire.

    Refilling toner cartridges

    If you can stand the mess, refilling some types of laser printer (and photocopier) cartridges can be worthwhile IFF the basic mechanism and photosensitive drum are in good condition. Even if you only get one more use out of a cartridge, the savings can be substantial. I have had mixed results buying reconditioned cartridges, but you know what your own have been doing in their spare time! However, it isn't quite just a matter of dumping new toner into a used cartridge:

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    Firstly the health/safety warning. Toner, because it's a very fine powder, is (a) carcinogenic, and (b) explosive. However, provided you don't make clouds of the stuff, you should be OK. It can't be *that* harmful, as some photocopiers take 'loose' toner, and some printers have separate toner/drum/waste toner units.

    I've fixed mechanical problems on the SX and CX cartridges. I also once moved a good drum from an empty cartridge to an almost-new cartridge with a scored drum (don't ask...).

    There are 2 things you need to do to refill one - empty out the waste toner tank and (obviously) add some new toner.

    The SX cartridge is easy to dismantle. Unclip a little triangular plate on the side, pull out 4 plastic pegs, and the case comes off. The plastic bung for filling the toner tank is obvious. To empty the waste toner, you have to take the cartridge apart, remove a plate (2 screws) and empty the toner into something. I worked inside a plastic bag last time I opened one of these cartridges.

    These printers use a combined toner and developer. The toner mix must be magnetic for the printer to work at all.

    I've seen bottles of loose toner for some photocopiers. I have not idea which brands would be suitable (if any), but I might experiment sometime.

    As for inspection/testing:

    Well, the main test is probably drum sensitivity (but this won't change unless you are swaping drums). Now, if you get that wrong, all that happens is that the image is too light or too dark. There are some little plastic clips on the side of the cartridge that operate microswitches in the printer. And there are only 3 settings!. Believe it or not, I've found some remanufactured cartridges that work better when these blocks have been moved - in other words, the drum sensitivity wasn't checked properly.

    Everything else should be mechanical inspection - condition of bearings/gears, leaks, primary corona, etc. Nothing that's impossible to do at home. Of course it's rather different if you're selling remanufactured cartridges - in that case you need to be sure the parts will last another 4000 pages or whatever. But if you're fixing up your own printer, and don't care if you have to fiddle with something else in 1000 pages time, then there's no real problem.

    About the worse that can happen to the printer is that the cartridge dumps toner all over the insides. I've had that happen - once. And it wasn't from a cartridge that I'd had in bits. It was from a remanufactured cartridge. That, together with the incident where a CX cartridge had had the door assembly incorrectly assembled, which caused damage to the transfer corona assembly, convinced me to avoid remanufactured cartridges that I'd not rebuilt myself, or at least checked.

    You do need to avoid mixing waste toner (which will probably have a higher concentration of developer) with the new toner. Empty out the waste toner tank, but don't add the contents to the new toner. But if the toner you are adding is similar (or better still the same) as the original stuff, there is no problem from the residual toner in the cartridge.

    Plenty of printers (Ricoh engine?) use 'loose' toner + drum/belt as separate parts. In those, you do add new toner on top of the old, and it all mixes up. Now, why should Canon printers be so different?

    Cleaning laser printer optical path

    As noted below, the optics are delicate and easily damaged. Use an air bulb to first blow off any loose dust/toner. Then use isopropyl alcohol and a cotton swab or lens tissue to *gently* clean the exposed surfaces. DO NOT disassemble any optics components - the alignment may be critical.

    (From: David H. (textool@aol.com).)

    It's always a good idea to clean the entire optical path from the laser (diode) forward. Most of this is inside the scanner module and there may also be a long external mirror.

    With time these surfaces become coated with a film of toner/dirt and the laser beam reaching the drum gets weaker and diffused. Print quality suffers and later "beam detect" or "scanner failure" errors will occur, which may be intermittent at first, but eventually they will shut the printer down completely.

    So open up the scanner module and gently clean all the prisms, mirrors and lenses. I say gently because the mirrors are front coated and the lenses may be plastic which can be scratched by aggressive cleaning with cotton swabs. Clean the external mirror if there is one. There is also a beam detection sensor which will have it's own small lens or prism which must be cleaned. Good luck.

    In my experience dirty optics has been the they most common failure in 4+ year old laser printers with Canon engines.

    Cleaning caked-on toner from printer and copier fuser rollers

    (From: alphamnemonic.)

    Fuser rollers can develop a band of baked-on toner which is difficult to remove because it is harder than the fuser's PTFE coating. I have developed a cleaning method which has worked well for me so far. First, wipe the roller with a swab or soft cloth and a few drops of isopropyl alcohol. Next, stick a piece of packing tape onto the roller where the toner has adhered and rub it so that it sticks well. Finally, pull off the tape in the direction of a tangent line to the curve of the roller so it 'snaps' off rather than peeling it off. It may take a few tries, but the toner should come off in large pieces. A blast of cold spray can help with stubborn deposits. It isn't necessary to remove the roller from the fuser with this method--just work in small sections and turn the roller a bit more each time.

    Laser printer drum damaged by extended exposure to light?

    (From: DenFrodo (denfrodo@aol.com).)

    Yes, with extended exposure. I remanufacture toner cartridges for a time. Long term exposure to light will effect the photoconductive layer. We even cover areas of some (scratched) after-market drums and exposed them to sunlight to see how it effected them. It takes extended exposure to show an effect. No, the printer will not detect the problem and the printer will probably print dark for the basic 'positive' image (a dark area is exposed to light) laser printer. A scanner or copier might print light (reflective light of the 'white' surface exposes the surface of the drum. Good Luck.

    Repeating images on laser printer

    This likely means a faint ghost of the main printout at a distance equal to the circumference of one of the rollers or photosensitive drum.

    Depending on where the problem originates, this could be a bad wiper (cleaning) blade, faulty corona, or incomplete fusing.

    It is easy to determine where the problem is located: Interrupt a printout in mid-stride (where part of the paper is between the toner/developer and fuser. If the un-fused image has ghosting, it is a fault in the area of the drum. Also see the section: Previous copy doesn't erase from drum.

    Black evenly spaced lines on laser printer or copier

    (From: Edward Klotz (eklotz@www.flash.net).)

    90% of the time it is the toner cartridge (or drum), If it is still exactly the same condition with the new cartridge, here is one exception: The fuser assembly has a rubber roller, I had one with an indentation in one spot, allowing toner to pack in the indentation & actually transfer a small character impression onto the fuser roller and then transfer it to the paper several times on each sheet. The fuser is very easy to remove(2 screws at the back). I temporarily worked the indent out of the soft rubber, but eventually replaced the fuser assembly.

    (From: Dave Lee (leedj@uwec.edu).)

    According to "Image Defects, Repetitive image defect ruler in LJ4", the cause would me the "Primary Charging Roller", is 1.5 inches or 38 mm around. Start with that, swap with another printer is possible, or order one, try Parts Now, Inc, 800/886-6688 or The Printer Works, 800/235-6116 or Global Printer Service, 800/588-3554.

    Optics disassembly?

    "I would like to remove the mirror in order to clean it well. It mounts on a plastic bar that runs the width of the printer. The bar mounts by screws (2) at either end. I am worried that I will need some kind of aligning jig to get it back properly."

    The short answer is: DON'T. Some aspects of the alignment are impossible to adjust/correct/reinstall without factory jigs and test equipment. The best you can hope for at home is trial-and-error. Most of the optics is probably solidly glued in place anyhow so disassembly is difficult or impossible - but it doesn't move much either! The long mirror itself is probably less critical than the rest but there is no real need to disturb it.

    To clean the optics, use (low pressure) compressed air, alcohol and lens tissue, or as a last resort, alcohol and cotton swabs (Q-tips). However, some lens and mirror coatings may be easily damaged - test in a corner first.

    (From: Pete (PTCull@lbl.gov).)

    You are correct in being worried. Alignment marks closest to the muffin fan side of the engine should be noted before removal of the Beam-to-Drum Assembly. Better yet, just blow the mirror clean with a filtered compressed air source, leaving the mirror mounted.

    Unless the mirror is very contaminated, I really wonder if you'll see the improvement you believe you might? Some of these mirrors have very soft surfaces and only should be touched with lens cleaner or cotton swabs.

    If you still choose to remove the mirror from the engine, check to see if the two extreme sides of the page seem even when referenced to the top edge, using the "Engine Test print".

    HP LaserJet FAQ

    If your problem is with an HP LaserJet, before reading further, check the following three sources of information:

    Guide to disassembly and reassembly of HP LaserJet II and III

    (From: Alexandre Souza (taito@terra.com.br).)

    I used to fix lots and lots of HP II and HP III here in Brazil. So, with time, I developed a "checklist" for HP II and III repairing, that is safe enough to keep the printer working for years (4 years and NO defects whatsoever) and customers were happy. I'll include things not necessary for Americans (Brazil is HOT. Hotter than USA!) because friends all over the world may need this info.

    What you need: Isopropyl alcohol, toner sucker, good screwdrivers, cotton, cotton swabs, screw picker (that little handy tool to pick/put screws in tight places), some rags - and lots of space!

    I'll take the HP III as an example, The HP II is equal, with very minor differences. Please apologize me for any incorrections, since I'm telling everything from memory.

    1. Be prepared to do a complete tear-down of the printer. Dismantle it to the last screw. This is a day-long work, so better you are prepared to do it. If you let for the following day, you WILL forget where the assemblies go, and will make your job a trip to hell.

    2. Take the body cover entirely off. You will take total 6 screws, one of them in the back of the printer. You take it off pivoting it on your direction. It is a clumsy process, don't know why HP didn't made it easier.

    3. Take the front "shield" off. The "front shield" is a big sheet of metal that covers the entire front of the printer. 5 or 6 screws, 2 ol the sides, 2 on the front, 1 or 2 on the top.

    4. Take the Power Supply off. You need to unscrew 2 screws on the front of the printer, and one on the back of the power module, besides the main motor. Also, disconnect the cable of the motor from the power module.

    5. Look at the solenoids of the power module. It is very common to have the solenoids' felts inside it became a messy glue. Take the metal flap off (take care with the coil) and clean everything that seems messy. Take 2 or 3 small squares of electrical tape, and put in the nucleus of the solenoid. Do it on both, replace flap. Don't forget the coil! Check the solder of the power module.

    6. Now is time to take the ozone filter support out. This is a black plastic piece with 2 screws - one on the top, and another near the motor. Clean everything with compressed air and a rag. Be sure the filter is unobstructed. Better if you CHANGE the filter, but these are impossible to be found in Brazil. So you clean it. Or you will have some messy ex-gears. You have been warned.

    7. Take the fuser out - it has 4 screws on the corners. Take care of it, there is a big and expensive lamp inside, and you don't want to buy a new one, eh? We will not disassembly the fuser module if not needed. But if you open the cover, pick the cleaning pad out and see black lines on the fuser roller, it is time for a cleaning!!! Dismantling the fuser is a complicated matter, but here we go: First of all, study how every piece fits its place. You should begin the dismantling by the right side, taking great care with the lamp. Take off the plastic pieces at the sides of the fuser, take the lamp out, so you are free to work. Store the lamp in a quiet place (no one should even touch it he he he) and don'ts touch the glass with your fingers - do it by the ceramic sides, or the wires. Clean the lamp with cotton embedded in isopropyl alcohol and set aside. Take off the locks of the gear on the right side of the fuser roller, there is an equal lock on the left. Take off the fuser roller, and PLEASE don'ts scratch it. You will see 2 thermistors on the fuser assembly, covered with yellow plastic. Clean it with cotton swabs and alcohol. If they are damaged (plastic is broken, missing a piece, has a hole, etc) CHANGE IT. If the surface of these thermistors isn't smooth, it WILL mark the surface of the fuser roller and WILL DAMAGE it. And this is not a cheap part. Everything clean, assembly it again, doing backwards what you did to unassembly. Remember this is a GOOD time to change the fuser roller.

    8. Take off the AC module, where almost all the CX engine problems are located :o) This is the aluminum "tower" besides the fuser assembly, and where the AC cable comes in. Dismantle everything, change the little little little heat accumulator (yep, it is so little that should be called "heat accumulator") from the black TRIAC besides the mains power connector, and put a good heatsink with heat paste there. Also, clean THOROUGHLY the upper fan assembly, because when it fails, it can make things hotter. Hot enough to melt the fuser gears. :o) Remember: ERROR 50 = TRIAC open. A TIC 226 fits the bill on place. Of course there are other causes for error 50. But I've never seen that in Brazil.

    9. Time to go to paper path! Take the 4 screws that locks the registration assembly in place. The registration assembly is the module where you have the big green handle. Clean everything and note if the "L" of the front is straight. If it doesn't make a 90 degrees angle, fix it. Also, change the separation pad. It is the culprit of 99% of the pickup paper problems. What? You live in Brazil and cannot buy new separation pads? So clean the black mess that was a long time before a hard rubber, and put some kind of rubber or cork on it. Also, take about 10 cm of isolating tape and cover the lower half of the "separation pad" you did. The printer will not give ONE pickup error for YEARS. BTW, I never had one return of this method. When you put the registration assembly back, don'ts forget the small yellowish piece on the front roller is assembled pointing the frontal part of the printer!!! This is very important!

    10. Take the pickup roller out and clean it thoroughly. Use turpentine to make it softer, it will last years! Of course, if you have a replacement unit, better to use that.

    11. Using a cotton swab, alcohol and LOTS OF PATIENCE, clean the corona wire. Be careful as you can, not to break the diagonal wires that surround it.

    12. Do a GOOD cleanup on the inside of the printer. Use compressed air (with a dehumidifier) and don'ts throw air in the scanner assembly. Better never mess with that. Only open the scanner assembly if you HAVE a problem with it. Hope you never have.

    13. Of course you already took the toner cart off, eh? Well, you have a black metal plate, with instructions of putting a cart there. Slide that plate to right, and move it up. You will see a very nice and delicate frontal mirror. Use only cotton and alcohol to clean that, and after only cotton to polish it. Make it clean, and close the lid. Of course, you don'ts want to let it exposed. A nick on this mirror, and there goes your print quality away.

    14. You have 2 contacts on the left part of the printer cover. They touch the fuser assembly below. Do a continuity test there, you should find some ohms, but continuity. If you don'ts find it, you have a broken "erasing lamp" inside the printer cover. 2 screws keep you far from them, better change it now

    15. Close the printer cover, turn the printer upside down, take out the plastic pan on the bottom of it, take the metal pan, clean everything including the lower fan. Of course, a lower fan broken, is a laser printer broken. NEVER, I said NEVER run the printer with the lower and upper fan disconnected, OK? Do you remember what I said? You have been warned 2.0 :o)

    Well, this completes my "HP Refurbishing method". To reassemble it, you do the following:

    And so you have a healthy HP III. It will last for YEARS if you did it right. don'ts forget to put a fresh new cart of toner and it will last forever. Of course, you want to clean everything externally too.

    The common disclaimers apply here. Do it at your own risk. I've fixed some 500 HP LaserJet IIs and IIIs, and never had a problem, return or anything doing that. Your mileage may vary. Greetings for Brazilian friends, and for all around the world that uses that guide. :o)

    Guide to disassembly and reassembly of HP LaserJet 4

    (From: Alexandre Souza (taito@terra.com.br).)

    I fell in love with this printer but this puppy got some Coke in her fuser and messed things a little. So I was obligated to do a complete disassembly of it, to clean up the mess and change a gear. So, here we go:

    1. Open the right lateral cover, pick it out.

    2. Take the top cover out, 2 screws on the back, one on the top, beside the little green brush. You have 2 plastic locks on front, be careful with them

    3. One plastic lock on top, and you take the left panel out

    4. On the back of the printer, take the big panel out - you have the plastic hinge besides the parallel and serial connectors (best done than said) and one small "lock" on the right pin of the door (the power supply side). Take the lock out, and slide the plastic door out the printer.

    5. 2 more plastic locks, and you take the small front panel (where you put cartridges) out. The only remaining panel is the MP tray, that I didn't needed to take out.

    6. Take the formatter door out. You have a small plastic pin on the middle of the hinge of it, push it and slide the door out.

    7. Take the formatter out. You will have 2 screws on the left, behind the formatter door hinge, one or 2 screws on the top, one in the right.

    8. You are seeing the main motor. 4 exposed screws, and it is out. Take GREAT care with a hole below the left screws, if you don'ts close it (and open before using the printer) one of the left screws ALWAYS falls by this hole on the power supply. And you don'ts want it, want you?

    9. Behind the motor board, you will find 2 screws, it frees the main gear unit. This is the most fantastic thing I've ever seen - 2 screws and all the gears, inside a module, come out. I LOVE HP! :oD

    10. Behind the printer, take 2 screws on the base of the fuser assembly, take it out, push up and back the fuser assembly.

    11. 2 screws on the printer connectors, let you take out the cooler fan on top of it. It also has a small plastic lock on the left side of it

    12. Take the black ventilation colum out. This is divided in 2 parts. Take care. Take the ventilation grid on the bottom of it, and clean it thoroughly.

    13. 2 plastic locks on the BACK of the assembly that transports the paper to the top of the printer (sorry, don't know the HP name) and it is free.

    To disassemble the fuser:

    1. take the FRONT plastic part out. Note there are 4 plastic locks on the front, and another one on the lower right, besides a gear.

    2. Unconnect a lug terminal on the bottom of it. Take GREAT care, this is the wire that comes from the lamp.

    3. Free all the wires from their locks, and take the two screws of the frontal thermistor (the bigger one) on the top of the fuser. Also, unconnect the small 2 wires with a connector on lower left.

    4. Unscrew the RIGHT plastic part, freeing the lamp, and with greatest care of all, unscrew the LEFT plastic part. TAKE CARE with the wires and the lamp. One wrong movement and the lamp is gone.

    5. Take the lamp out, now you can play it safe with the fuser.

    6. Take the right top and bottom gears - they are free.

    7. Take the fuser gear. You have a small lock you have to take out.

    8. Take the same lock in the left side

    9. Take out the metal cover of the fuser - you have 2 small locks between the plastic back with the green sticker (that has 2 coils that go to this cover), just pull it back and here comes your metal cover. Clean the thermistors!!! don'ts forget to change it if they are scratched, dented or damaged!!!

    10. Unscrew the fuser roller bushings from the main fuser module

    11. Find a way to make the lower rubber roller stay far from the fuser roller, and pick it out of the module. So you can pick out the black rubber roller too

    12. Clean everything with isopropyl alcohol

    13. Reassembly everything in reverse order.

    This is my method of "Refurbishing" the HP4+. Note I have one with 400,000 pages printed and NO problems. The gear I changed was INTACT (as the others on the main gear module) with only 2 broken teeth caused by the roller, that was completely locked!!! It was SO Glued with coke that a small gear on the fuser, after unassembling, was completely unable to move, before taking it out with great force, and cleaning with alcohol. After that, it was free as a bird. Go figure...

    Just a little fun: This one cost US$30. :o) Spent more US$40 to fix. The parts were more expensive than the printer itself he he he :o)

    Testing the erase lamps on an HP LaserJets

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    There's a very quick test for the erase lamps in these printers (SX engine). Open the cover, and swing it right open. There's a plastic post that comes down from the cover at the back left with 2 contacts in it. It goes into a slot on the left side of the fuser when the printer is closed.

    Check for continuity between the 2 contacts in the cover. I have no idea what the right resistance would be, but it's less than 1k. If it's open-circuit then most likely one of the lamps is burnt out. There are 5 of them, in series.

    If the lamps are good and there are still erase lamp problems, then remove the fuser, take the cover off the left side of it (1 screw on top) and unscrew the PCB under it. Check the 2SD1414 power transistor Q331 on this board (it's the erase lamp driver). If that doesn't do it, check the components around it. R335 (1.8 Ohm) is the current sense resistor in Q331's emitter circuit, L331 is a filter choke in series with the lamp supply, and Q331 is a current sense transistor that removes the base drive from Q331 if the thing overcurrents.

    I suppose it could be a problem with the cable back to the DC controller or even the DC controller itself, but that's unlikely.

    If you've still not found the problem, though, post again and I'll think again.

    HP LaserJet error code 51

    "On self-test, pulls in paper, pauses, indicates "51 err." Then pulls paper through mechanism while "02 warming up" is displayed. Nothing prints, except for 2 horizontal black bars about an inch apart with grey in between them, about 1/3 from top of page. Since we stole this fair and square, and since we have a number of good (but _not_ laser printer) techs around, I'm wondering where we might dig. The book simply says error 51 means we should call HP service."

    (Note: In the discussion below, the specific cable and parts IDs may not match your model.)

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    It's called a 'beam detect error'. Let me explain what that means:

    The laser beam is reflected off a spinning hexagonal (I think) mirror, and scanned across the drum. At one end of the scan the laser is turned on, and the reflected beam hits a fixed mirror (not the drum) and is reflected down an optical fiber to a photodiode on the DC controller board. The electronics on that board detects the pulse from that photodiode and provides a sync signal for the data sent to the laser

    So the fault can be the laser, the scanner motor, assorted optical bits, the photodiode, or bits on the DC controller board. I think we can eliminate the motor for the moment, as that tends to give Error 52s.

    Look at the PrinterWorks Web site (http://www.printerworks.com/) for exploded diagrams. Also read the section: SAFETY since you will be inside the printer near high voltage and possible exposure to laser light.

    The official fix is to replace the scanner, the cables (electrical and fiber optic) between the scanner and the DC controller, and then the DC controller until the fault goes away. But you can often fix things

    Start by pulling the casing. Over the paper tray there's a flat black box. Start be reseating the 2 cables (one under the flap) that go to this unit.

    If you have an IR detector (as used for testing remote controls) then undo the screw on the scanner - not the fixing screws that hold the scanner in place - remove the grey optical fiber, and hold the sensor over the channel that the fiber fitted in to. Do not look up this channel - it can output laser light. Turn on, and try to print a test page - which will fail.

    If you get IR light out of the scanner unit:

    Reconnect the fiber at that end, remove the base of the printer, and arrange some way to prop it upright with the interlock switch pressed in. Unplug the fiber from J201 (a DNP-like connector) on the DC controller board. Put your IR sensor on the end of that and test again. No IR light now, time to replace the fiber.

    Reconnect the fiber to J201 and hook a logic probe or 'scope to TP208 on the DC controller. This is the output of the photodiode amplifier. Do you get pulses here? If not, check the photodiode and the transistors Q202, Q204, Q208. If you do, then, alas the problem is most likely in a custom chip, and it's time to replace the DC controller.

    If you get no light from the scanner, then it's time to inspect it:

    Carefully trim back the moulded clips that hold the cover on the scanner and open it up. Clean the optics with a soft brush or lens tissue. The mirrors are front-silvered of course. There's a little shutter in the laser beam, opened when a toner cartridge is locked in place - is this opening correctly when you close the printer? If not, find out why not.

    Unplug the cable from the laser PCB, power up the printer and try a test page. Does the scanner motor rotate? If not, we'll debug that.

    The last possibility is that the laser isn't coming on for some reason. Debugging that is going to be interesting (read Sam's laser diode notes next :-), and I'll do the same) and I'll try to talk you through that when I know it's necessary. (Note: Sam's laser diode notes -- Diode Laser chapter of Sam's Laser FAQ.)

    (From: Tom Dunn (dunnt@cco.caltech.edu).)

    Error code 51 indicates loss of laser beam for over 2 seconds. Check -5 V, also make sure there is no interlock mechanism damage, and +5 V at J451-1 on Laser Drive PCA. You may need new laser unit. Good hunting.

    (From: John Holcepl (john_holcepl@nls.net).)

    This is a very common error on a HP Series II. An error code 51 is loss of beam detect. The cause is a bad cable between the DC Controller and the laser/scanner assy. P/N RG1-0908-000CN. Sometimes just reseating the cable will make this error go away but it will come back eventually.

    (From: Eric Liber (liberes@westinghouse.com).)

    Here is the description of the possible 51 errors:

    51 ERROR (Loss of Beam Detect)

    HP LaserJet I fuser swapping and other tidbits

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    What you need to do (if you're going to remove the whole assembly) is to remove the (brown) cover that's flat on the printer chassis just behind the 'tower' at the front that contains the interlock switch and AC control boards (where you removed the fuser heater wires from). Under that cover there's a little 4-way connector that links the fuser thermistor back to the engine control PCB (DC controller). Unplug that.

    Then you can remove the 4 screws that hold the fuser in place, lift it up a bit, and free the heater wiring from the channel in the baseplate. The whole fuser then comes out.

    These fusers can be stripped and rebuilt - I've done it. If the old one still heats up, keep it for the heater lamp that's in it - that lamp does fail, and it's not that hard to replace. It's a quartz-halogen bulb, so you shouldn't touch the 'glass'. The safest place to store it is in the old fuser.

    These printers are that bad. I've had one stripped down to individual components (even dismantled the optical assembly), and have it running now. But the SX engine (LJ2, etc) are a lot easier to dismantle into modules (and in some cases harder to replace individual components on...)

    HP LJ Series II bad bearing noise and other comments

    "Got one that started making unpleasant noises about two weeks ago. It is in a church office environment, so they have to turn it off unless they need it for a short while. I took part of the cover off and decided it wasn't the top fan or the small motor on the right side. The sound comes from the right rear at the grilles at the bottom of the machine. It sounds like a bad bearing or something rubbing a fan."

    (From: Ralph Wade Phillips (ralphp@techie.com).)

    Bad lower fan. Part number RH7-1056. I'd check at http://www.pcservice.com and register and order XX-RH7-1056 (it's under $20) and just replace that fan.

    I'd also consider replacing the upper fan (go look for it with the search engine - it's about the same $ for the generic 3rd party version) since a failure there will ALSO cost you the fuser gears, thereby costing a fuser assembly.

    As to removing the bottom cover - Eh? Put the top back on, flip it over, and remove those screws you see around the rim. Remove all cartridges also. Slip the metal cover off, and viola - There she is!

    Big warning - Do NOT run the machine with the lower fan disconnected. This is known to damage the DC controller board (at least a $60 part, EXCHANGE - over $300 purchase!), and can cause massive problems later down the road ... Take a look at http://www.printerworks.com and look (and print, if possible!) their exploded parts diagrams. Yes, books are available, but will outrun the $150 the church is paying for it (worth it, though, with as many LJ2/LJ3/QMS/LWII and other SX-based printers out there, IMAO.)

    (From: Al Savage (asavage@iname.com).) Probably the most-commonly-replaced part is the lower fan on the 33440A. Yes, it's very noisy when bad, right up until it becomes extremely quiet .

    Well, buying 10 year old hardware and then wanting to depend on it not breaking isn't very realistic. As reliable as the LJII/III is, they DO break, especially lower fans, the 14T fuser gear, paper pickup roller, pickup photosensor, AC power supply, registration assy. It's just that they'll commonly print half a million pages in the process, and many contemporary printers aren't designed for a service life a third as long.

    To replace the lower fan, have a vacuum cleaner with a brush handy (or an air compressor). Remove toner cartridge/drum unit. Close lid, remove all cables (power, data), flip printer upside down. On a LJII, you're looking at steel square pan; on a LJIII, you're looking at a large plastic tray and you have to remove four Phillips-head screws to get it off first.

    On both models: remove any optional memory card(s) by first removing the access hatch for them on the left side. This hatch is the one *without* the 1/4" hole in it. Remove any circuit board you find under there: they just pull straight out.

    On the back of the printer, remove any optional I/O card (HP JetDirect, Appletalk, etc) that may be installed next to the normal Centronics data port. This isn't always *necessary* but when it isn't it just makes things easier. Once again, just remove two screws and pull on the I/O card.

    Now you can remove the lower pan. Nine Phillips head screws later, lift the front edge of the pan, wiggle it to get it off over the Centronics port cable clips.

    Vacuum the pan out -- it will be filled with dust bunnies -- and any dust you see collected on the mainboard. You can now see the lower fan. It's a squirrel cage design. Remove the short wire harness and the four screws to remove it. Note the position of the small bracket under two of the screws, as you will need to put that bracket back!

    Reassemble in reverse order. One screw on the lower pan does NOT go in the left rear corner, but that's only a problem is you have the upper plastic off as well. You can't put it in wrong if the upper half is still assembled.

    The fan is about $20 wholesale, often close to $40 retail. Do NOT attempt to disassemble and clean it. I've tried several times, and no matter what I try it will either still be noisy, or will fail again within months.

    HP LaserJet II just dies and no sign of power after a short while

    (From: Larry Sabo (sabo@storm.ca).)
    "I have an HP LaserJet II that will just die after a short time. There are no power lights, not even an error message. If I leave it for a short time it will come back on after a power cycle. It is totally random."

    Check the daughter board in the PSU at fault. On mine it had deteriorated solder connections on *both* ends of the connecting pins. Remove it, resolder the pins on the daughter board, then remount it. It's worked like a charm ever since.

    HP LaserJet II with dark bands on first page

    (Problem and solution from: Ken Eckert (eckert@sfu.ca).)

    I have a LJ II that has the following problem:

    "The problem is a dark horizontal band starting at line 1, about 1/2" wide, indistinct edges. Repeats down the page at same length as the optical drum circumference. Problem is present only on page 1 of a print job. All other pages are clean. When the engine is stopped at the beginning of the print process a large amount of toner is present on the OPC in a band. Band gets darker and larger the more time between successive print jobs is incurred.

    Swapping cartridges has no effect."

    The problem turned out to be the chassis wiring harness from the DCA controller to the HV module. There was a bad connection between the HV module and the chassis connector only when the module was inserted. I ended up extracting and soldering all the crimped pins in the connector. I suspect that it was probably the HV reset line that was the problem.

    HP LaserJet II output jam

    "I found a junked HP Laserjet II which initially jammed pulling in the paper. I have fixed that. It still jams on the output, though. It prints nicely, so it seems worth fixing. If I open the back tray, the sheet exits 90% before stopping with the "paper jam" error. With that tray closed, I get the accordion paper jam in the fuser area. I do not detect any rotation of the upper rollers to feed the paper out of the top. When opened, I can roll them by hand easily. I see no obvious gear wear or broken teeth. I also see deep scratches in the grey fuser, which is probably unrelated. The toner does not have any fusing problem that I see in a band down the page."

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    I think you've got 2 problems here - the false paper jam with the tray open, and a problem with the drive to the top rollers.

    Let's look a them in that order.

    There's only one paper sensor in the SX engine that I know about, and that's part of the fuser. On the PCB at the left side of the fuser there's a slotted opto-switch with a lever that detects paper in the fuser. There's also a single transistor on said PCB that buffers/amplifies the output from the opto-switch, Q332, I think. This sensor must change state one way (to indicate paper has got to the fuser) shortly after the registration clutch operates and then change state the other way when the paper has got out of the fuser.

    You might start by reseating the cable at J206 of the DC controller board (just in case it's bad connections) and then look at the sensor (mechanically and electrically) on the fuser PCB.

    Silly question: If the paper tray switches (on the DC controller board) aren't operating properly, could the printer think it was feeding a shorter piece of paper than it actually has, and then give a paper jam error? It's always possible... Alas I don't know the coding for these 3 switches (SW201-SW203)

    The other problem is almost certainly mechanical. Look at the gears on the right hand side of the fuser (stripped teeth do occur here) and in the top cover of the printer. Shouldn't be too hard to find where the drive has failed. I suppose you could remove the outer casing and AC block, re-insert the fuser and close the cover, and look at things while turning the machine by hand.

    HP LaserJet IIp won't go past 'warm up'

    "I have an HP IIP that goes through the "05 Self Test" mode but hangs when it gets to "02 Warm Up." The only thing I ever hear run is the fan. I am not getting any error codes otherwise. If I try to send a print job to it in this state, it seems to take it and the On Line indicators light up, but it won't print. Based on what I've read in the FAQ and in the archives, I'm guessing it is the DC Controller. I re-seated the connections going to the DC controller PCB and the power supply and everything else visually looks good. I do not have a service manual for this unit.

    Can someone tell me how to test the DC controller to see if it is defective or maybe shed a little light on what may be causing the unit not to make it to the "ready" mode?"

    Any number of simple faults can result in the warmup sequence not completing. Check these first before suspecting a blown power supply or controller.

    It may indeed be as simple as a burned out bulb or broken door interlock.

    (From: Dave Lee (leedj@uwec.edu).)

    Here is what I found in my notes concerning your very same problem, Hope it helps......

    New "Service Today" from Parts Now, volume IV, number 1, issued in Feb 95 is devoted to the "LX" engine units, IIP/IIP Plus/IIIP Series, the Cannon LBP-4, Apple Personal LaserWriter. Lots of good stuff, error 50's, error 41's, fuser upgrades, "moaning", other squeaks etc.

    Here is what it says:

    If hung on "02 Warming Up", trouble may be caused by cables on the door wear and tear. Also look at DC Cnt PCA, dual I/O, formatter PCA. Now also look at the solenoid for the MP pickup roller assembly. This can cause the 'hung 02 Warming Up' error if an open occurs in either the solenoid cable, or solenoid coil. To check, remove the formatter PCA in order to access the DC Controller PCA. Locate J209 on the DC Controller; pins 1 & 2 are the solenoid. Measure across the top of these pins, the correct reading is 200 ohms +- 10%. Replace the paper path door cable assembly, Part #RG1-1608-000 if the solenoid has high resistance.

    (From: Jeff Churchvara (jeffc@pond.com).)

    Experience would have diagnosed this one in about 10 seconds. I just didn't know what I was looking at.

    I started reading the FAQ and figured the worst. At first, I did not have the service manual to go over this code. When I finally did get a copy, I started checking the voltages and did not have +24 V at the DC Controller PCA.

    All of what I was reading said to defeat the door interlock. At first, this didn't make sense to me because the bar that should be attached to the door was instead, laying on top of the switch and wasn't even moving when the door opened. I didn't know enough not to look any further.

    Once I realized the bar should've been attached to the door, I started looking for it's correct mounting. The screw holding the bar must have loosened up and over time it broke the mounting nut right out of the door.

    I ended up resetting the nut (threaded sleeve) by adding a screw from the outside. Then I pinched it in place with a second screw when I re-anchored the bar. This made the bar pull away when the door opened and then correctly contact the interlock switch when the door closed.

    I forgot the basics of troubleshooting when I posted this one and was making it more difficult than it actually was.

    Thanks to all of you who responded and kept me looking in the right direction.

    Totally blank printout on laser printer or copier

    (From: Ed Paolo (edpaolo@intac.com).)

    Check to see if the image of the printout to be, is on the image drum. If it is there and isn't being transfered to the paper then something like the high voltage corona wire or hight voltage supply isn't charging the paper.

    (From: FAXFIXR (justdfax@cdepot.net).)

    There are two corona wires, the charge corona and the transfer corona. The charge corona is the one you should look at. It is located in the toner cartridge so the easiest way to check is try another cartridge, even one that is out (or almost) of toner. If you don't have another, then you can check yours. If you look at the cartridge in it's operating position, there is a black mylar plastic film that covers a slit on top from end to end. The mylar covers the corona wire but allows you to insert the little green tool, found inside the copier, to wipe the corona. If the tool is there, stick the pad into the slot and wipe it back and forth. If you hear a slight screeching sound (like a violin) then the corona is there. If it's not there, then the cartridge must be replaced.

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    (The following was written for HP LaserJet III but it is generally applicable to other laser printers and photocopiers.)

    For starters, try a new toner cartridge. I've found these can cause all sorts of problems...

    Now, blank pages are due to one or more of :

    1. The drum is not getting exposed by the laser
    2. The EHT power supply isn't transferring toner onto the drum
    3. The EHT power supply isn't transferring toner from the drum to the page.

    Start it printing a test page (the 'engine test' switch on the DC controller is useful for this). When the paper is still going through the printer, turn it off, open the lid and pull back the cover over the drum in the cartridge. Is there a 'latent image' on the drum? If so, check the EHT power supply and transfer corona assemblies.

    Check that you plugged the cables into the scanner properly. They don't always make good contact. This will normally cause a 'beam detect' problem - I forget what the error is for that (51? 52?). It's possible that there's an O/C in the cable, of course.

    If you have an IR detector (of the type used for testing remote controls), unplug the optical fibre from the DC controller and point the end at the IR detector. Again print a test page. If the laser and scanner are working, you'll get some IR (laser light, so take care) out of the end of the fibre.

    There is a mechanical shutter in front of the laser in the scanner that's opened by a lever under the scanner when the cover is closed with a toner cartridge in place. The idea is to prevent any laser light getting out if the printer is run with the cover open/no cartridge. Is this working correctly. Did you get the scanner correctly on top of it.

    Bearing replacement on HP LaserJet II to fix error code 41

    (From: Andreas Mohr (a.mohr@mailto.de).)

    My (donated) Laserjet II series printed black horizontal lines after about the third sheet. It then occasionally spit out "error 41".

    Solution:

    The ball bearings of the scanner unit were defective (now I know that my printer was MUCH louder than other HP 2s). That caused the scanner unit to get "out of sync" and print black lines and occasionally spit out "error 41".

    I just replaced the ball bearings and everything was fine again.

    As far as I know, no Laserjet error codes service page mentions this yet. (They only say that "the scanner unit may be defective", but not HOW that may be.)

    HP LaserJet series II - error code 50 Service and clicking

    (From: Andreas Schumm.)

    There's a Web page that has photos and a description of the disassembly to get at the faulty component(s) for error code 50. See Repairing the HP LaserJet Series II power supply.

    (From: Sam.)

    As you'll find out reading below, many different failures can result in the same error code, so don't just assume that what the author of the Web page found is the same as your problem!

    (From: Peter Strezev (jup001@airmail.net).)

    I had a LaserJet series II with exactly the same symptoms: 50 SERVICE and that very clicking sound. I fixed that printer last week after quite a bit of troubleshooting.

    First: the clicking sound comes from a mechanical relay in the PSU, which controls, together with an SCR solid-state relay, the sequence in which power is applied to the heating lamp in the fuser. The sound itself is not a problem, it is a symptom. You probably have a bad thermistor in the fuser assembly, or the signal path from the thermistor to the control board is corrupted.

    If you are good with electronic troubleshooting, try the following:

    (From: Mark Wolfe (markw@wwa.com).)

    Just to speed things up a little, override the printer open switch, and remove the plastic cover from the right end of the fuser to get at the power connector for the bulb. Turn the thing on, and read this connector, should see about 115 VAC, if you don't, check Q101 in the Power Supply. The problem you had sounded like a rarity, as it's usually the halogen light in the fuser, or Q101 in the power supply. Yours was the sensors going back to control Q101. Anyway, if you ever have one of the power supplies opened, it looks as if HP intended this triac to fail with it's whimpy heat sink. Hope this helps.

    I had the same thing happen to me on a IID, check the connections on the fuser. I swapped fusers with my III, and both printers worked, swapped them back and both printers worked. The power connector on the right end of the fuser seemed a bit loose, could've had a bad connection. Anyway, IID is still going, and this was in august when I did this.

    (From: Chris Holmes (holmesc@sedgehill.lewisham.sch.uk).)

    I dont know if Error code 50 is the same as Service 50 on the HP Laserjet II but if it is you are in luck.

    I once had this and spent about an hour and a half stripping cleaning and reassembling it, and it worked! When I got back to civilisation I checked the manual. The official HP action for Service 50 is - switch off for 10 Mins!

    Still i'm sure the clean did it good.

    (From: Frank Reid (reid@indiana.edu))

    A fuser-heating fault in HP Laserjet II or III (or the Apple equivalent) causes a capacitor on the dc controller board to charge. Discharge takes 10 to 30 minutes. If you repair the problem and restart the machine before the capacitor discharges, the error indication remains.

    (From: Stuart Elflett (stuarte@OntheNet.com.au).)

    Does the 50 error now stay on constantly, e.g. if you turn the machine on after a 30 minute wait, does it still say 50 error without doing its self test?? If so, I'd head towards the D.C. Controller. If the bulb in the fuser comes straight on, and the delivery rollers don't turn a little before hand, I'd be looking at the AC Supply. Is your fan spinning?? A stalled fan can often result in a 50 error. Is the fuser heating up?? If you're technically minded, you could remove the fuser and check the bulb for continuity.

    Parts are commonly available almost world wide now.... you could check my links page for some sites that provide parts.... there's plenty more out there that aren't on my list..... try a web search for Laser Printer Parts....... They're not too expensive, as long as you get exchange parts where possible!! A manual would be a good purchase if you intend doing the work yourself, however they are still relatively expensive compared to parts!!

    (From: David Gardner (gardneda@www.gc.cc.fl.us).)

    Error 50 is called a fuser error, which it is, but I have found that it can also be caused by a bad High Voltage power supply or by a bad cable that runs from the power supply to the fuser.

    Notes on HP LaserJet II error code 50

    (From: ROO7L@aol.com.)

    When confronted with a code 50 - after checking lamp, lower fan operation, thermal cutoff, wire connections etc. I always, as a precaution against call-backs, 1. remove solder from wire ends at thermistor, clean and resolder with silver solder, 2. replace 1k ohm resistor under pin connector (thermal protector board on end of fusing unit), 3. replace Q101 (triac on power supply board ) and add more heat sink, 4. replace D155 on dc control board. 5. restake all wire end connectors with stake type wire connections. All of these are prone to happen and you can cut them off at the pass by taking care of these common offenders while you have the machine open. The voice of experience, I hate call backs!

    HP LaserJet II - Top of the line printing shifting in multipage printing

    (From: M K Ramadoss.)

    Problem: In multipage printing, the first page will print fine. But, the top line of the second and subsequent pages will be shifted about 1/2".

    Cause: There is a solenoid on the right side of the printer which stops the toothed gear. You can see this if you open the printer cover exposing the inside of the printer. On the solenoid there is a thin piece of foam which becomes sticky with age and temperature inside the printer. When the second and subsequent pages are printed, the solenoid the metal flap sticks to the solenoid and hence the timing of the feeding of paper is messed up and hence the shifting of printing.

    Fix: This is very simple. In the hardware section of your store you will find thin felt squares or rounds with self-adhesive back normally used on the bottoms of lamps etc to prevent them from sliding as well as scratching polished surface of table etc. All you need is one such piece (about 1/2" round) which is stuck on the solenoid side of the solenoid. Thin felt is preferred. (Cost of a sheet of felt rounds/squares at Walmart is less than $1.00. All you need is one round).

    HP LaserJet II bad bearing sounds

    This also applies to many other laser printers using the Canon SX or similar print engine.

    "Developed frequency-changing whine of bad bearings. Not really sure whether a fan motor or main motor."

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    A service manual probably wouldn't be a lot of help. The SX printers (HP LJII, Apple Laserwriter 2, etc.) are very modular, and AFAIK, the official way to repair them is to replace the defective module. Of course it's possible to repair them at a much lower level than that, which is what I do to my pair.

    There are 3 motors:

    1. Lower fan. A tangential blower in the lower case next to the DC controller (Engine controller) PCB. This runs all the time that the printer is turned on. (Maybe the cover needs to be closed - I can't remember which 24 V line it runs from)

    2. Upper fan. This sits on top of the AC block in the rear right corner (near where the mains cable plugs in). It runs when the machine is printing, and drops back to a slower speed when the machine is idle.

    3. Main motor. This is a stepper motor that drives all the mechanics in the printer through a gear train. Needless to say it only turns when the machine is actually printing.

    By finding out when the noise occurs, it's possible to figure out what is causing it.

    Firstly the good news. I have never had a main motor bearing fail. They're ball races anyway (Yes, you can strip the motor down and rebuild it). I've never had noise from the gear train either.

    Now the bad news. Fan failure is common. The bearings are bronze bushes, and they fail. Sometimes lubrication helps a lot, sometimes things are just too far gone.

    Lower fan. Remove the toner cartridge and paper tray. Turn the printer upside-down and remove the screws that hold the base cover on. Remove the cover. The fan is obvious, and is held down by 4 screws (there's a bracket at one side that comes off as well), and it plugs into the smaller of the PCBs in the machine. Remove it. You can then unscrew the motor from the fan and slide the motor + blades out. Then pull the blades off the motor, remove the circlip, and pull the motor apart. Examine the shafts and bearings. If they're not too badly worn, a drop of oil (3-in-1 or similar) will probably cure the fault. Otherwise you need a new fan - parts are impossible to obtain.

    Upper fan. Remove the paper tray and toner cartridge. Undo the screws and remove the outer casing. Remove the 2 screws and lift out the fan duct + ozone filter (on top of the AC block). The fan is under it and is held down by 3 more screws and a 2-pin plug on the upper (fuser protection) PCB in the AC block. There are at least 3 different upper fans in use, so I can't give directions for dismantling them. But in general, the motor can be unscrewed from the side of the fan, and the bearing on the other side pulled out. Inspect them as above, and try a drop of oil.

    Editor's note: If you buy a replacement for this, it will likely be a 24 VDC muffin style fan (like in your PC, except that is 12 VDC). HP or Apple will likely charge you $70 or more for this part!

    (From: Frank Reid (reid@indiana.edu).)

    If the upper fan fails, the fuser assembly will overheat and do about $200 damage. Cleaning the bronze bushing often solves the problem.

    An obscure and obnoxious squeak sometimes comes from the anti-static brush on the end of the upper fuser roller (end opposite drive gear). A bit of high-temperature grease on the nearby felt pad will fix it.

    HP LaserJet II fuser overheating

    (From: Glenn Allen (pclogic@xtra.co.nz).)

    I had this problem on my HP LJII. I traced it to D155 shorted on the Fixing Heater Saftey PCB , this is in the same casing as the AC Power Assembly where the power cord plugs in. There was some sort of corrosion there.

    I replaced it with a IN4148 diode as it is only a signal diode.

    HP LaserJet II triac replacement

    (From: John (jneff@uidaho.edu).)

    We have been replacing these with a SK10466 (800 V, 8 A, Vgt 2 V, Igt 50 mA).

    (From: dhickey@knox.edu).

    If it is in the AC Powersupply, try a NTE 56006.

    Also check for 2 open resistors.

    HP LaserJet Series II intermittent

    "My new (to me) HP Laserjet Series II printer seems to have a power supply problem, although its previous owner said his supplier/servicer suggested the problem was 'probably due to a fryed mainboard' and promptly sold him a new printer. Lucky me. :-)

    It works fine for a while, then starts to cycle between "12 Printer Open" and "00 Ready" before the fan in the power supply area drops in speed at the same time. I notice that the lamp on my desk flickers occasionally, even when the printer shows "00 Ready". Tapping the cover at any time immediately brings on the "12 Printer Open" message and fan speed drop-off. The cycle eventually ends with a "67 Service" message."

    (From: Larry Sabo (lsabo@freenet.carleton.ca).)

    The cause of the problem was an intermittent connection in the DC power supply, where the daughter board is attached to the pcb with a right-angle connector. I got so tired of removing and reassembling the power supply, I just jammed an empty plastic scotch tape role to hold it in position, and it has worked like a charm ever since.

    HP LaserJet IIP printer error code 12

    (From: Michael (action@netdoor.com).)

    Your problem is likely to be the "Density Control PCB" that if you had the top cover off the unit, it would be a little board with a lot of wires (mainly purple, I think) going to it. It is in the front on the top.

    About $40. Not saying that's it for sure, but I've seen it three times in the last 4 months.

    (From: Frank Reid (reid@indiana.edu).)

    I agree, but it could also be the assembly of photoelectric sensors and their wiring harness (about $25). Before replacing components, clean the sensors with compressed air and re-seat their connectors on the DC Controller board.

    (From: Greg Smith (n6nyx@cox.net).)

    Check the 10 uF electrolytic capacitor on the Density Control PCA board to clear Error 12 Open or No EP.

    The capacitor on my printer went open-circuit big time! It started off with an intermittent error message. Percussive maintenance brings it back for a while, then it dies for good! The capacitor is only rated at about 16 V. I put in a 10 microfarad, 50 volt unit to replace it and still had plenty of room to clear obstructions after I bent it over a bit!

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    I am not sure how the printer detects that the cover is closed - there are 2 obvious ways : from the +24 V interlock switch or from the toner cartridge microswitches. Since, I believe, it'll claim the cover is closed even without a toner cartridge in place, I think it's the former.

    OK, things to check:

    Firstly, there should be a little peg on the cover (on the right hand side under the edge) that goes into a slot on a metal housing on the LV power supply module. This presses a microswitch inside that housing. This peg often breaks off.

    If that's not it, then take off the bottom cover from the printer and stand the printer on one side. It's safe to power it up like this. Connect a voltmeter between the 2 outside pins (1 and 14) on J212 (a long 14 pin socket on the DC controller board). Power up. If you don't get 24 V here, you have a LV power supply problem.

    Now connect the meter between pins 2 and 13 on the same connector. If you don't get 24 V now, then the problem is almost certainly the microswitch in the LV power supply, or the peg that operates it, or something like that. You can probably fix that by taking out the LV power supply, taking it apart and examining the switch and its connections.

    If you do get 24 V there, then assuming the printer uses the +24 V sensing as the method of detecting when the cover is one, the problem is possibly R817, R818 or C760 on the DC controller board. If it's not those, then it's IC218, a custom microcontroller.

    As I said, it _might_ use the toner cartridge switches to detect when the cover is closed. Take off the upper casing, the frame round the front, and the LV power supply module. On the side of the power supply there's a PCB with the paper sensors, the clutch solenoids, and the cartridge switches on it. Check the latter (SW301 and SW302) and the spring leaf that operates them.

    HP LaserJet IIP with 12 Open or no EP error

    "I have tried to reseat the EP-L cartridge and opened and closed the fuser door many times, but can't seem to get this printer to work."

    (From: Erik Welander (erikwelander@hotmail.com).)

    I have written a detailed description of how to repair the "Error 12 OPEN or no EP-L" problem of the Lasejet IIP that seem to be very common on this printer (cost of approximately $1 for the capacitor). This, and some general maintenance advice can be found at: HP Laserjet Maintenance and Repair.

    (From: Terry (tmredding@worldnet.att.net).)

    Sometimes the spring tabs on the left side of the printer that are the sensor for the cartridge get bent or are dirty. Also you get this error if the fan is not working.

    (From: Dave Lee (leedj@uwec.edu).)

    Most times I find that its the Density PCA that causes the problem. Sometimes its just dirt/dust in the two sensors on the right side above the toner cartridge, blow these out and give it a try. Density Board is avail through most laser parts houses, these are the ones I use:

    HP LaserJet IID Error 13

    (From: John H. Meyer (John_Meyer@compuserve.com).)

    (I finally found the cause of the problem described below: One of the voltage outputs on the main power supply was blown. Had the power supply refurbished and everything works perfectly.)

    "LaserJet IID gives Error 13 message immediately upon warmup. (This is paper jam message.) The paper path, however, is totally clear. I've taken things apart and cleaned the exit sensor and paper path. Unit is quite clean. I've downloaded information on Error 13 and have tried everything except replacing DC controller card ($200-$400 part). I took the unit to two different repair places. One tried swapping out the fuser assembly -- that didn't help, and that was all they were willing to do for their free diagnosis. MicroAge charge me $$ for a few hours troubleshooting and tried swapping out the main motor. No help. They also claim to have electrically checked the exit sensor. They said that the only thing left was to replace the DC controller card, but they didn't have one to swap in, so I'd have to pay up-front for the card.

    I didn't do this. Instead, I took the unit back home and pulled the DC controller card. I tested all the discrete parts (simple diode tests on the transistors), and they all test OK. Two questions:

    1. Does anyone have other suggestions of things to try?

    2. Does anyone have a recommendation on where else to get a DC controller card for less money?"

    (From: Dave Lee (leedj@uwec.edu).)

    Had almost the same problem about a year ago, problem was the AC Power Module, just needed reseating. ACPM is located in right rear corner, just under ozone filter and upper cooling fan. Fuser assembly must also be removed to get to one of the 4 screws that hold the ACPM to frame. Remove the ACPM and then put back in place, thats all I had to do. Has been working since Feb 1995.

    But another thought about this, are you sure that something isn't jammed where paper from botton tray comes up just in front of the registration assembly. If you remove the reg. assembly, there is a clear plastic guide that is held in place by 2 screws. Remove this and check to see if maybe something is jammed by that sensor.

    As far as a good price on DC Controller board, I would call Parts Now, Inc. at 1-800-886-6688 or The Printer Works, 1-800-235-6116. I know that Parts Now sells either repaired or used or exchanged boards, probably a LOT less than what you were quoted.

    (From: John Meyer (john.meyer@worldnet.att.net).)

    Thanks for very complete reply. Your message sparks a lightbulb. When I first took the cover off when this problems initially surfaced, I took the power unit apart from the top (took of the little fan, and then started disassembling it). When I put it back together, things worked. I then put the top main cover back on, and things didn't work again. Nothing has worked since. However, I never took the whole assembly out and therefore never got to the connector. I'll try this and let you know what happens.

    I don't use the bottom tray because the bottom paper path is prone to jamming, and has been for years. However, it is possible that someone (I have a four year old boy) may have jammed something in there. I have looked for such a jam and haven't seen it, but based on your input, I will try again.

    (From: Dave Lee (leedj@uwec.edu).)

    As far as the jamming from bottom tray goes, 2 areas to look at:

    1. Remove the registration unit, its the first assembly inside the printer. Open cover, its the part with the hinged assembly with a small green handle. (Not the fuser, this is right inside the printer). Remove both paprer trays, registration assembly is held in by 4 screws. Under that is clear plastic guide held in by 2 screws. Remove this guide, and you should be able to inspect path from bottom tray for an obstruction. Also check the clear plastic guide, something may be caught in the guide.

    2. Paper pickup roller for bottom tray may be glazed or very dirty. Clean with damp rag (water will work) although some "Fedron" cleaner is best but hard to find.

    Do this after you get the error 13 fixed so you don't compound the problem.

    HP LaserJet IIP and LaserJet series 2 error code 52

    "I have a HP LaserJet IIP, which does not print, but displays Error Code 52. Don, a man who is willing to help me fix mine, has a HP LaserJet series 2 that works. How similar are theses two machines? Is there any chance that one can swap parts to find the problem?"

    (From: srob@iprolink.co.nz and Michael Schuster (schuster@panix.com).)

    Totally different. Different cases, electronics, toner cartridge and system.

    (From: Lewis King (echo@infogo.com).)

    Error code 52 is 'Scanner Malfunction' and there have been posts on the USENET newsgroup sci.electronics.repair that indicate that this is fairly common and is usually the cable leading to the scanner mechanism. These printers, and the CX before them, use insulation displacement connectors. Quite often the connection gets flaky and pressing down on the wires where they enter the connector will fix a problem (worked on my Xante Accel-a-writer when it was telling me I needed a new DC controller board).

    The part you need is the scanner motor... I can't remember the part number, but it is the same as the scanner motor for a IIP+ and a IIIP. The scanner motor has three screws holding it in, in the box where the laser attaches to the side. As you pull off the scanner you will notice a square microprocessor on it's board. the bottom side of that board will probably have a dark spot where that processor got too hot. I fixed about 50 of them that way.

    I will find out what the error code means and get back to you.

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    That sounds like the classic scanner motor failure on these printers. It's a very common fault, alas.

    The 'Official' repair is to replace the scanner assembly (the entire unit - the black plastic box - on top of the printer), and if that fails to cure it, then change the DC controller board. But you can normally fix it a lot cheaper than that.

    Here's how (I believe) the unit should work:

    There's a frequency generator (FG) coil on the motor PCB, just like the one in a VCR. The signal is fed down the cable to J203 on the DC controller and then converted to a TTL signal by IC202A (LM393 comparator). It enters the gate array (IC206) and comes out again when it is fed to a TC9142 chip (IC203) which compares it to a reference clock also from the gate array. The error output from the PPL is conditioned by IC201b (LM358) and fed back to the scanner motor. There is feeds the control input of the TA7259 (IC401) chip which drives the motor windings.

    First check that the cables are connected to J203 and J401 (inside the scanner unit). The most common fault is that IC401 has failed and probably burnt out R401 (8R2) with it. Fortunately, this chip is not custom - in the UK it's available from (e.g.) Grandata, so a VCR spares place might have one.

    If you've still not got it working, get back to me, and I'll talk you through the test points on the PLL on the DC controller board. Hopefully the gate array is still good, since I've not found a source of those.

    Oh yes, how to dismantle the scanner to replace the chip.

    Firstly remove the outer casing from the printer. Then unplug the 2 cables on the scanner unit - one on J451 (on the laser PCB) and one on J401 (under the little flap on top). Undo the clamp screw in the back right corner, swing up the clamp and remove the beam detect fibre cable. Then remove the 4 screws and lift out the scanner unit.

    Now, *carefully* cut back the melted-over studs and lift off the top cover. Keep dust to a minimum (obviously). Remove the circlip on the scanner motor spindle on the bottom of the unit. Remove the rotor and hexagonal mirror, taking care to note where all the washers go. Remove the small screws and lift out the PCB.

    (From: Flemming (flemming.gottsche@get2net.dk).)

    Where the scanner cannot maintain proper speed. Replace electrolytic capacitors on scanner board. All capacitors are 10 uF/16 V. Also replace the current measurement shunt resistor (R301) on scanner board. It has a value of about 1 Ohm. All these parts are in the black plastic box below processor.

    HP LaserJet II scanner information

    (From: Jon Fick (JFick@pcilightingcontrols.com).)

    The following Web site has some helpful hints about scanner chip/board replacement, and also has a scanned datasheet for the chip for those that want to substitute flatpack/dippack types.

    HP LaserJet IIP error code 51

    "I have here a HP Laserjet IIP which gives errocode 51. The manual says something about a beam-detection. Do you guys 'n girls think this is to repair for relatively little money?

    (From: Osceola Electronics (osceola@netonecom.net).)

    On my IIP+, I had to take it all apart. I had to remove the main board and open the main cover to the laser area and clean the fiber-optic pickup and lens.

    HP IID error code 50

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    A problem on the DC controller (in particular C210) can cause intermittent ERROR 50's

    Mechanical failures of the fuser will not cause ERROR 50 (AFIAK). After all, the fuser temperature is maintained even when the mechanism is not turning. A broken gear in the fuser will cause paper jams, but not much more.

    If you've got the machine in bits on the bench, and you are *sure* the fuser is not overheated, try shorting C211 on the DC controller board momentarily with the power off to clear the error.

    HP LaserJet IIP+ error code 50

    "My owners manual tells me that if this error persists after a 15 minute power interruption then service is required. Is it feasible for me to perform this service myself? What is the risk factor that my printer will be FUBAR if I attemp this?"

    (From: Don Hickey (dhickey@knox.knox.edu).)

    It could be one out of a number of items that are actually bad. Most likely it is the fuser assembly. However it could also be the Ac Power Supply, Dc Controller or the cable going from the fuser to the dcc. Most of the time the lamp on the fuser burns out or one of the thermal switches.

    (From: (Frank Reid (reid@indiana.edu).)

    Test for continuity through the large terminals on the fuser. That will tell you if the lamp and thermostat are good. If they are, then the problem is in the AC power supply (cubical box under the upper fan). Remove the printer case, observe the fuser lamp upon power-on. If it lights immediately and then goes off with an audible click, the triac in the power supply is shorted. ECG 5620 is a replacement. Be careful desoldering the plated- through holes.

    HP LaserJet IIP - 52 error

    "The problem with the machine is as follows:

    1. I bought the printer used from friends a year ago. They sold it because the printer would crash when they sent it a large print job. I do that very rarely, and thus this happened very infrequently. I would just shut off the power and then turn it back on and it would print the same job just fine.

    2. In December the printer would go through the initial diagnostic routine, but when the first print job came it would at first sound fine, but then make a longish whining noise and then display the error message "Printer Error 52" (I looked that up in the Users' Manual: "This error message indicates a scanner malfunction.") I reset the printer, and then it would work fine.

    3. The problem as described in 2) gradually occurred more frequently: I would have to reset the printer several times for it to print. After it started to print it would work fine until I turned the printer off for some time.

    4. Finally even after letting the machine warm up for hours it would not print at all, even though it went through the diagnostics on power-up.

    5. Model Number of the laser printer is: HP33471A, manufactured: April 1990 Serial Number: 3049J01EOB

    (From: Charles Kyle (kyle@citynet.net).)

    I have repaired a lot of the HP IIP printers with error 52. It has always been the scanner motor assembly. The assembly can be repaired by replacing the motor driver IC and possibly a burnt resistor or by ordering the scanner motor assembly.

    Laser Impact carries the scanner motor assembly for the HP IIP. The part # is RG1-1771-000. it is easy to replace and costs about $60. Their phone number is (800)879-5882.

    "I have a HP Laserjet IIP printer that no longer works and I need some help diagnosing. The printer does not print any text pages but instead gives an error 52 on the LCD screen. The owners manual says that an error 52 is a scanner malfunction. However the authorized service center said that this error was a memory error. The cost of having them fix the printer is more than the printers worth."

    (From: Rich (richcar@flash.net).)

    The service center gave you the wrong info. It is a bad scanner motor or a bad dc controller. I have found, that on a lot of laser printers for this error and others, that if you re-seat all connections internally, to all PCB's, the problem will go away. (About 50% of the time) If this doesn't work you can check the voltages on the dc controller itself. The dc controller is the PCB under the formatter, (If you were looking down on top of the printer) and directly above the scanner assembly.

     J212 on the dc controller
    ------------------------------------------------
     Pin 1: Gnd (blue)
     Pin 2: Gnd (blue)
     Pin 3: +24 * (red)	
     Pin 4: +24 * (red)	
     Pin 5: Gnd (blue)
     Pin 6: +12 (orange)
     Pin 7: Gnd (blue)
     Pin 8: +5 (brown)
     Pin 9: Data signal (yellow) (shouldn't matter)
    
    * Paper path door closed or pwr supply interlock defeated

    These are the voltages the dc controller uses. (From the pwr supply) The scanner assembly. is the most expensive part and on exchange you can get one for about $150-200. But don't quote me on that. Contact Printer Works or PC Service Source to find out. I don't have their numbers but you should be able to get them from the 800 directory. 800-555-1212

    HP Laserjet IIP error 52 - chip replacement

    (From: Jon Fick (fickpci@aol.com).)

    I was finally able to fix the printer by replacing the chip on the scanning motor board rather than replacing the whole board. That's a $10 fix rather than a $80 fix!

    The surface-mount chip and an associated surface-mount resistor apparently run hot in this application, and over time, darken the back of the printed circuit board.

    I covered the scanner rotor before attempting anything because I didn't want to have to clean the mirrors afterwards.

    I also have the same chip in a different package that might actually be more robust. It is the HA13456A, a long DIP package with triple-width ground tabs in the middle of each side. It is electrically equivalent from what I can tell and might be a good substitute if the flat pack fails early.

    The printer came right up, and self test immediately printed two pages!

    The chip came from: B & D Enterprises International, PO Box 460, Main & Liberty Streets, Russell, Pennsylvania, 16345.

    Their worldwide number, as well as tech support (really helpful) is: 814-757-8300 (800-458-6053 in the USA).

    Their 24-hour fax number is: 814-757-5400

    VISA, MASTERCARD, AMERICAN EXPRESS are accepted worldwide.

    Each chip was $7.55. They have a $15 minimum order, so I ordered two, partly to make the minimum order, and partly to have a spare.

    Laserjet IIP PS board

    (From: Brian Mathews (icontech@volcano.net).)

    I have repaired many of these power supplies and I usually replace the triac, two resistors (22 and 150 ohms?) and the eight pin DIP (usually marked SHARP).

    HP LaserJet III problems

    "This LaserJet III has me stumped. It has a persistent error 50. I tried everything in the service manual, but to no avail. If anyone has an idea how to fix this, it would be most welcome"

    (From: Ted Szypulski ( szypulsk@esslink.com).)

    Sounds like an open fuser lamp, like mine was. I have an LJ4. HP would only sell a rebuilt fuser assembly. My cost was $150.00. The fuser assembly on the 4 comes out the rear real easy. There are two captive screws to loosen and then it just unplugs. I removed mine and took it to another LJ4 just to be sure that was the problem before buying a new one. My testing with an ohm meter also proved the fuser lamp was open.

    I hope the LJ3 is similar and this is of some help.

    Smudged vertical line on HP Laserjet III

    (From: Dan Bourque (danbou@nbnet.nb.ca).)

    The common problem with these printers is that the fuser drum gets scratched by the heat sensors of the fuser assembly which gets dirty with toner. Take a look at the drum of the fuser if the protective coating was scratched to the metal. If this is the case then the fuser needs to be replaced (around $80.00 for refurbished). If the protective coating is not scratched to the metal then the fuser can be removed and disassembled to clean the heat sensors. Use alcohol and Q-tips to clean.

    To print a test page hit the On_Line button to put it off-line and then press test button for about 5 seconds.

    Shifted print on HP LaserJet III

    "The LaserJet III in my office has acquired the annoying habit of shifting its printed output about half an inch down on the paper. This sometimes cuts off the page numbers. It typically will never happen on the first few pages. Once shifted, it stays that way, until I turn it off. I'm kind of clueless, the manual doesn't mention anything like this."

    (From: Frank Reid (reid@indiana.edu).)

    Replace the pickup roller. Clean the transfer rollers with naphtha or mineral spirits. If that doesn't work, replace the transfer assembly (set of metal and rubber rollers after pickup roller; removable by 4 black screws). Inspect the solenoids on the DC power supply: The rubber pads sometimes become sticky and hold onto the armatures, thus messing-up the timing. If that happens, scrape the old pad off, clean the armature and core with solvent, and replace the pad. I use squares of double-sided foam tape and then use naphtha to remove the glue from the outer side. If you remove the old pads but don't replace them, the printer will be more noisy, and permanent magnetism in the solenoid cores may affect timing.

    (From: Joop van der Velden (joopv@solair1.inter.NL.net).)

    Two possibilities: a mechanical problem with the paper transport, or a escape sequence reprogramming the printer paper format(ting)

    Try to print some test pages from the printer itself (no pc connected) If that gives the same problem, try cleaning the paper path and transport an paper separation mechanism.

    (From: Randy McVittie (rmcvittie@octrf.on.ca).)

    I thought it might have been the pick-up roller, at least that is what the manual was pointing me towards, but other people's 2 cents worth said to look at the solenoids SL301 and SL302 on the Paper Control PCA.

    There is a piece of foam tape on the core of these solenoids, and it had become kind of sticky, preventing the solenoid from snapping back when power was removed. Then I had severe paper jam problems I guess you need some amount of spacing here. So I put a few layers o of electrical tape in the same spot and now I had great registration. 3 layers of tape was my magic number, your mileage may vary.

    This area was not even mentioned as a source of problem in paper registration troubleshooting chart in the HP manual.

    HP LaserJet III powers on but appears dead

    "When I flip the power switch on, I can hear it power up, but the none of the lights comes on and the LED panel is also dead."

    (From: David J. Pittella (ddc_pitt@ix.netcom.com).)

    Since you say the unit 'powers up', I assume you hear the engine power up (fan, drive motor, etc). Assuming this is a Lajerjet III (not IIIp or IIIsi, etc.), you can do an engine test by removing a small cover on the bottom of the right side, removing this cover will expose a metal plate with a hole in it. The hole exposes a switch on the DC controller which will print simple line test pattern. This will at least confirm that the engine is working.

    The front panel LCD display and status LED's are driven by the formatter board. The formatter gets its +5 power from the DC controller via (2) screws that secure the formatter to the CD controller. If you remove the bottom plastics and bottom pan, the formatter is the large main board. The DC controller is the smaller board with several connectors attached to it.

    I am also making the assumption that the cable leading from the formatter to the front panel is attached at both ends?

    You may also want to remove any options, (memory, optional I/O) as one of these options could be preventing the formatter from initializing and possibly lead to a blank display. BUT, the best guess here is that the formatter is not getting power - check those screws between the DC controller and formatter!

    HP LaserJet III cold fuser

    (From: Flemming (flemming.gottsche@get2net.dk).)

    Where the fuser is cold and the relay trips, check Q153 for leakage (C-B) which results in current leaving the base and charging C158. When C158 is charged to about 3.3 V, Q153 is turned on and the relay trips.

    The relay that is tripping is RL101, which actally is located on another PWB than the transistor. This relay has a very distinct sound, which has been mentioned over and over again in postings to various news-groups. Both PCBs are placed in the rear right corner of the HP LJIII.

    HP LaserJet III paper jam

    "I have two LaserJet IIIs that complain about a paper jam on power up, right after the self test (i.e. before I've even had a chance to send anything to the printer)."

    (From: Terry (tmredding@worldnet.att.net).)

    The most likely cause of this problem is the exit sensor arm or photointerrupter or the dc controller board. Standing in front of the printer with the top cover up it will be in the far left lower corner.

    (From: Wong Sy Ming (siming@singnet.com.sg).)

    HP LaserJet III paper feed problem

    My LJIII wouldn't feed paper past the registration assembly. Sounds like a mechanical problem right? No, it was not mechanical but rather it was electronic problems. At first I replaced the two drive transistors on the solenoid board thinking that one of them burned out but that didn't solve the problem.

    Then, the whole thing came apart as I traced the connections for one of the solenoids back to the DC controller board. Guess what? One of the PCB traces near the 78324 IC (large square one) was corroded away. I quickly soldered a wire across it and now it works perfectly! Now I wonder what could have caused that...?

    HP LaserJet III error 50

    "My HP Laserjet III is giving a "50 Service" error. So something is wrong with the fuser. But the lamp is not burned out. Also, the fuser roller is pretty clean.

    When I turn on the printer, the light in the fuser comes on for a second. Then there's a click from the power supply (or around there), and the light goes off.

    The 05 Self Test message comes up.

    Then Warming up (takes a while).

    Then, both online and page feed lights go out and "50 Service" appears.

    The power supply and fan are working and the ozone filter is clear."

    (From: Geir Knutsvik (geirk@netpower.no).)

    What about the fuser? Does it make heat? I have in some cases have faulty opto electronics for sensing paper and drawers result in Error 50.

    In worst case it cold be the main pcb ...expensive... check dc controller.

    (From: Mark Wolfe (markw@wwa.com).)

    5 bucks says it's Q101 in the power supply (crosses to NTE 5620). I've seen quite a few where this was the problem. Check the power connector at the right end of the fuser, it's under a plastic cover. There should be about 115 VAC there during the warm up, you'll have to stick something in the cover open switch to get it to power up. If there is 115 VAC, it's the lamp in the fuser. If there isn't 115, it's save to say it's Q101 which is the triac that supplies the fuser. Get a new heatsink with the new triac. Cost here with tax to fix the problem is $7.07 + my labor. :)

    (From: Terry (tmredding@worldnet.att.net).)

    This error can be caused by missing 24 v, bad Thermistor, Fuser Bulb or Thermoprotector. Replacing the fusing assembly is quite easy by removing the 4 silver screws that secure it.

    Notes on HP LaserJet III error code 50

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    [Error 50, SX Engine]

    Remove the fuser (4 screws hidden down holes - it helps to remove the plastic cover from the left hand side (1 screw).) At the right hand side there's a 2 pin plug that goes into the AC block. Test for continuity between the 2 pins on the fuser. If it's open, then it's either the fuser lamp or the overheating-protection thermal switch that's open. It's pretty easy to trace the connections and test them separately if you can figure out how to dismantle the fuser (I can talk you through it).

    If the fuser is OK, then remove the outer plastic casing, and the AC block under the upper fan [at the right rear of the printer. Remove the two screws securing the black plastic ozone filter housing, pull that housing straight up and off. Three vertical screws secure the base, plus one horizontal one on the outside rear. Then pull the AC block straight up. The fuser must be removed prior to removing the AC block].

    Most of the time the thing that fails is the Triac, Q101 on the lower board in the AC block. This means the fuser can't heat up.

    Here are a few notes on what goes on in the AC block (totally unofficial, BTW).

    Lower board:

    R101, L101, C101, C102, C103 form a mains filter. The output of that goes to CB1 (circuit breaker) with VZ1 connected across the output of that lot as a spike suppressor. The output of that goes to the 2-pin plug (J104) and thence to the DC power supply. Watch out for J104 if you run an AC block out of the printer as it carries live mains.

    The fuser control circuit on the lower board isn't complex either. The live side of the mains (output of CB1) goes to T101 (current sense transformer) primary. The other side of the primary goes to the contacts of RL101 (fuser protection relay). There's a snubber SQ101 across the relay contacts. The other side of the relay contacts goes to one pin of J103 and thence to the fuser lamp. The other pin of J103 (and thus the other side of the fuser lamp) is returned to the neutral side of the mains via the triac Q101. This is triggered by SSR101. Oh, there are a couple of resistors (R102 and R103) in the triac gate circuit, and suppression components L102 and SQ102.

    There's a 10 pin connector between the lower board and the upper board. The pinout seems to be:

     Pins 1,2    T101 current sense transformer secondary
     Pins 3,4    RL101 relay coil
     Pins 5,6    Solid State relay (SSR101) input (6 +ve)
     Pin 7       Fan control
     Pin 8       Fuser drive from the DC controller
     Pin 9       Ground
     Pin 10      +24 V (input)
    

    The last 4 pins are connected to the 4 pins of J101 which is connected to the DC controller. Shouldn't be hard to trace those.

    Upper board:

    This virtually never fails, so I'll simplify the description by missing out resistors, etc. You can trace the signal flow from this description anyway.

    The fan control is trivial - the fan control input drives Q159 with the fan as the collector load.

    The fuser control signal is AC coupled (C157) to Q157. The output of that is rectified/smoothed (D157/C156) and drives Q156. The collector load of Q156 is SSR101 on the lower board.

    There's also a protection circuit, which works as follows. Normally Q153 is on which turns on Q152 and Q151. This turns off Q155 which has the protection relay as its collector load.

    If the fuser control circuit fails so that Q156 stays on too long (which would cause the fuser to overheat), then C153 is discharged by D155 and the collector of Q156. This turns off Q153, Q152, Q151 and turns on Q155, energizing the protection relay and turning off the fuser.

    If the fuser takes too much current then the output of the sense transformer T101 becomes large enough to trip the comparator IC151 (LM393). This turns on Q154 which discharges C153. The rest of the circuit operates as above.

    (From: Jon Martin (jon.martin@unisys.com).)

    There is a partial Schematic of the AC power supply at: Fuser Controller RG1-1438.

    The fuser thermistor comes in on pin 4 or J206. There's an 18k resistor (R237) to +5 V, and a 4.3K resistor to ground via SW205 (which is open when the base cover is on the printer -- the idea is to shut the fuser down if you power up the printer when dismantled). Then there's a 3.3K resistor in series (R747). And then a 4.7 uF cap (C210) to ground to smooth the signal out a bit. Finally we get the AN0 input on the main microcontroller IC218.

    The fuser drive signal comes out on port PD2. This is buffered by IC219e ('04) and IC211e ('07) before going to pin 2 of J208 and then to the AC block.

    There is one more bit of circuitry to consider -- the overheat shutdown. If the fuser overheats (or the machine things it has), then a signal comes out on port PD3. This turns on Q210 (2SC1815) which charges C211 (100 uF) via R749 (330 ohms). There's a 4.7M resistor (R748) in parallel with C211, which gives a time constant of many minutes. That's why to have to leave the printer off if the fuser seems to have overheated. Anyway, the voltage across C211 is monitored by the AN3 input on the microcontroller

    So, what to check? C210 is a favorite, it goes leaky. If that's not it, check (with the printer assembled and therefore SW205 open -- you have to solder wires onto the points so you can look at the signals) the following

    1. The voltage across C210 (should be around 2 V I think). If wrong, check the fuser thermistor and connections, the R's and C's between it and the microcontroller, etc

    2. The voltage across C210. If it's more than 0 V, then switch off, discharge C210 (short the leads together), try again. If it rises again, find out if Q210 is being turned on (Check the base voltage -- it's an emitter follower). If so, then either the microcontroller is faulty, or there's a problem you should have spotted in (1) :-). Check Q210, the R's and C's, etc.

    3. Any pulses at the input to IC219e (pin 11 of IC219). If not, then again, suspect the microcontroller if you've got this far. If you do have a signal there, check it again at the output (pin 10) of IC219e, then the input of IC211e (pin 11) and the output of IC211e (pin 10 -- this should be a 24 V level signal, not TTL). If you get a signal at the output of IC211e, then make sure it gets to the AC block. If it does, then the fuser should work.

    If the microcontroller is faulty then as far as I know, the only place to get a replacement is off another DC controller board.

    Paper jams on HP LaserJet IIIP

    "More and more I get HP Laserjet IIIP printers here with all the same problem: 13 Paper jam. Every time I look at the driving-mechanism and move it with my hand, but it all seems to work fine. I suspect there's a common cause to all this. I think it's got something to do with the electromagnet in the tray, but I'm not sure."

    (From: Frank Reid (reid@indiana.edu).)

    If the paper is getting crunched accordion-style, the 'drum-drive clutch' is probably broken. It's a couple of small white gears inside the right-side cover of the machine. The plastic tends to crack in a ring, separating the gear from the shaft. To confirm, mark the green drum in the toner cartridge: If it doesn't turn, then the clutch is surely at fault. Apple "Personal Laser Writer" and some other brands use the same print-engine.

    If the machine won't pick up paper at all but the pickup rollers are good, look for a bent piece of metal preventing movement of the bar that raises the stack of paper just prior to pickup.

    A third possibility is stripped plastic gears on the fuser assembly.

    (From: Lars Arvidsson (arvid@plea.se).)

    My guess is the paper intake rubber reel, you see it if you pull out the paper tray. It gets old and dry, and it needs to be sticky to get a grip on the sheet. It gets worse at dry weather, cold and dry. Try to clean it with alcohol, then coat it with some balsam turpentine (don't know if this is the right translation, it's a liquid used for diluting artist oil paint).

    Allow it to be absorbed for a few hours, then wipe of the excess. The reel is sticky again...or just replace it - but that's no fun. ;-)

    (From: Rick Norton (RKNORTON@worldnet.att.net).)

    I repaired an HPII with a similar problem using automotive belt dressing on the rubber pickup surfaces. Spray a small amount on a rag and wipe on surface. Allow to dry for 15 minutes. The printer has been working for 3 years without a problem.

    (From: Dr. John Betts (Dr@browser.demon.co.uk).)

    Don't ignore a more mundane cause - that paper is stuck inside the fuser, particularly if someone has used inferior grade labels.

    HP LaserJet IIIP power up problems

    "I have a HP Laser Jet IIIp, The problem is when it is switched on, the printer can do one of two things; the panel lights up and displays 05 Self Test and then switches off after around 3 Seconds, and other times nothing happens at all."

    (From: Pete (PTCull@lbl.gov).)

    If you have a voltmeter, J212 on the DC Controller is a good place to start checking. Blue wires are earth/ground, brown is +5 VDC, orange is +12VDC, and the red wires have +24VDC.

    However, it sounds like a nice time for known good spares or another known good LX engine to borrow known good assemblies from.

    HP LaserJet IIIP - error code 52

    "I have inherited a dead HP LaserJet IIIP printer and would like to hear your thoughts on its chances.

    The machine goes through its warm up routine OK but if I do an internal font printout or print from a PC then it sits quitely for about ten seconds, then raises in pitch for a second and simultaneously displays: 52 ERROR.

    The manual states that this error is a 'scanner fault'.

    I have dismantled the unit down to the laser and rotating mirror but can see no obvious faults. Perhaps the motor that drives the mirror is burnt out or the laser is dead??

    HP have quoted me a repair price equivalent to a new Oki!!!

    (From: Frank Reid (reid@indiana.edu).)

    That symptom can often be cured by re-seating the cables between the laser assembly and the dc controller (smaller board under bottom cover). Also check the optical fiber running from the laser scanner housing to the dc controller: Sometimes it goes bad or the end gets dirty. If you can shine a flashlight through it, it's probably ok.

    (From: Ralph Wade Phillips (ralphp@prysm.net).)

    About 50% dead laser and 50% bad DC controllers (photoreceptor dies, or interface chip it drives is dead ... gives SAME error!)

    Without a spare printer for parts, it'll cost you about a new printer for parts ... sigh.

    (From: John Fiskio-Lasseter (johnl@yin.earlham.edu).)

    Not necessarily. There are a number of places where you can simply buy the parts themselves, often refurbed - even a DC controller and laser assembly together would be cheaper than getting another printer.

    Adam, at a guess, I'd say that you really are looking at a failed laser/scanner assembly. Of the possible causes, that's the part that gets the most wear and tear, and the most likely to fail under normal operating conditions.

    A few places to try for parts:

    Both PW and LI will do repair, parts sales, and exchange parts sales, and you may find them a good bit cheaper than Hewlett-Packard.

    Also note that the engine parts from all other HP LaserJet II's and III's are interchangeable with yours. So are the engine parts (except the DC controller) from the Apple LaserWriter II printers. Other printers based on the same Canon SX engine are: QMS 410, Brother HL-8e, and several others that I can't remember off the top of my head.

    (From: Steve Pepin (steve.pepin@mogur.com).)

    You may not need to dump the printer or even pay for a new scanner assembly. I had exactly the same problem with mine and it turned out to be only the cable that attaches the scanner assembly to the main PCB. It's only a $28 part and you can possibly simply repair the one you have. I don't know how mine failed, but that is what our local HP service center replaced.

    (From: Frank Reid (reid@indiana.edu).)

    Correct! I repair at least 100 of those things per year. The connections fail far more often than the $canner. The problem can usually be solved by removing and re-seating the connectors on both ends of the cables that connect the scanner and laser to the 'dc controller' board (smaller board under bottom cover).

    (From: TAltmeyer (taltmeyer@aol.com).)

    Sometimes the driver-IC for the mirror motor is defect. It's a circuit from Hitachi HA1XXXX, i can't remember the number exactly. A half year ago i had such a printer with error 52 and i replaced the chip and all was fine.

    The chip is a little bit difficult to get but if your're encouraged enough you can get it (after a lot of telephone talking) from your local hitachi distributor. It's much cheaper than a complete unit :).). The scannerunit itself was made by Canon (as the complete printerdrive is made by Canon)

    Replacement for top output roller on HP LaserJet IIIP

    (From: Chet Valdes (chetvaldes@yahoo.com).)

    Rather than buying an expensive genuine replacement top roller when the rubber degrades beyond hope, it can be refurbished using commonly available sections of fuel hose, sized so it is a snug fit on the shaft. I learned this by experimenting with various types of hose, then I broke down and bought a kit from a guy on eBay for a couple of bucks that simply contained sections of pre-cut fuel hose! It worked perfectly, and should last much longer than the original foam ones. I didn't measure the shaft diameter, but I reckon there is a choice between a fractional inch size, say 1/4", or a metric one. If you're afraid the hose stub may slip, a tiny drop of super glue on the ends should lock it to the shaft. That's my penny pinching tip of the day.

    HPLaser Jet IIIsi - 'User Maintenance' message?

    "What cause a working HPIIIsi coming up with 'User Maintenance' message in the lcd window. If you pop up the cover and reclose, the message goes away and printer keeps on printing fine."

    (From: Jim Hunt (jhuntjr@b-c-i.com).)

    I believe this is the message you get after printing 200,000 (I might be wrong) copies which is a reminder to replace the fuser unit. This comes in a kit with new pickup rollers and several other pieces. It is pretty easy to replace

    HP LaserJet 4 - intermittent error code 50

    (From: Brian Mathews (icontech@volcano.net).)

    I have seen this problem quite a few times and I check the fuser lamp to find it was manufactured by USHIO. After replacement with a Toshiba lamp (not an endorsement, just what the supplier sends) the problem is gone. I haven't ever had this problem and not found that brand of heat lamp in the fuser......

    HP LaserJet 5L grabbing more than one sheet of paper

    (From: Shaun Harwood (shaun.harwood@virgin.net).)

    I'm a field engineer and deal with quite a lot of printers. What is quite a common cause for this problem is damp paper or using the printer in a damp room. Try a brand new ream (direct from store) and try using in a warm room and see if the problem goes away. I've been having this problem a lot lately as the weather has turned a bit - most of my customers store the paper in store rooms and it gets a bit damp. Incidentally HP printers in particular seem to be suffering from this quite a bit.

    More on HP LaserJet 5L paper feed problems 1

    (From: Jim Dempster.)

    An older HP LaserJet 5L has a tendency to misfeed sheets of paper. I took my unit apart to try to understand the problem and have successfully corrected it: it is now working properly.

    It turns out the paper feed mechanism is based on an eccentric rubber- coated cam to grab and feed the top sheet in the paper feeder. Over the years, the rubber on the cam tends to dry out/harden and get dusty, so it doesn't grab the paper properly like it did when it was new. The root cause of this is the cheap plasticizer in the roller has evaporated, allowing the roller to harden.

    Cleaning with alcohol only cleans off the surface dust and so won't restore the rubber to its original "sticky" state.

    To restore the rubber to its slightly more sticky state a different solvent is needed, with the intent that it will not only clean, but will slightly swell and recover some of the original stickiness.

    What solvent to use? Solvents that would eventually crack destroy the rubber roller should be avoided, but they need to be aggressive enough to cause some slight swelling (and thus stickness). Xylene is safe (ref. link below), however I used contact cement solvent thinner(a mixture of toluene, acetone, hexane, and N-butyl acetate).

    Just pull the toner cartridge, and with a Q-tip, clean the main rubber roller (there is only one) all over. Don't be afraid to let the solvent 'soak' the rubber, not only to help cleaning, but to slightly swell the rubber. You don't really need to be careful to wipe off the excess - it will evaporate on its own.

    The other things that help with printing is making sure the paper is placed right side up (the paper has a preferred printing side), using a slightly heavier paper stock (I use 24#), and keeping the paper feeder full.

    Info on various cleaning agents can be found at Cleaning Methods For Helical Scan Recorders Perhaps a routine maintenance with a solvent clean will suffice if misfeeds again.

    A little caution is necessary: if the roller was soaked instead of wiped, it might be possible the rubber would crack - still, it is better than throwing the printer away.

    The rubber restorer is pretty mild stuff - it used to be made from Freon, but since that is banned, they are using xylene. You can get xylene at the hardware store in bulk or under the name "Goof Off". Xylene is really pretty safe stuff, both from the rubber standpoint and from the user safety standpoint. See the Rubber Renue Material Safety Data Sheet.

    Contact cement isn't that much more aggressive, just different, and might respond differently to different rubbers. Almost all rubbers found today are synthetic rubbers (SBR, NBR, EP) because of cost and durability. Just as long as too much solvent is not applied at a time (a wipe isn't very much), then it is unlikely to attack the rubber.

    Some rubbers are attacked by oil-based solvents (like chloroprene), but these rubbers are selected for different purposes (like extended service in water). If we knew what kind of rubber was actually used (there are a lot), we could select a compatible solvent, but the printer manufacturers are likely to pick a rubber compatible with "rubber restorer".

    More on HP LaserJet 5L paper feed problems 2

    (From: Jim Dempster.)

    Just a interesting paper mis-feed followup - I did clean my rubber paper- feed rollers on my HPLJ5 and it did help to get the paper started (see previous section), but there were still some mis-feeds half-way through. I'm an engineer, so I decided to get to the bottom of the problem and REALLY took the laser printer apart.

    What I found that causes the mis-feeds is a worn "spring-wrap" clutch on the rubber roller shaft. The root cause: the HPLJ5 is a "top-feed" printer, and if FOR ANY REASON there is a mis-feed, the frustrated USER jerks the paper back out the way it came in (instead of properly pulling it forward along the paper path). Makes sense, right?

    Naturally, the paper being pulled forward by the rubber roller/feed shaft resists such pulling backward. There is a spring-wrap clutch built into the feed shaft that "releases" and allows the paper to be pulled back against the direction of motion without destroying the gears, but in my case, the prior user had pulled out SO MUCH paper that they wore out the clutch.

    It had enough "pull" to start the paper feed, but not enough to reliably feed it all the way through (it was at that transition point where it was starting to fail). Adding more paper in the bin helped, but it just wasn't reliable.

    It is really difficult to try to "tweak" the spring in the clutch to grab tighter (because the deformation point is very close to the fracture point), so the practical answer is to take another working spring-wrap clutch from another failed HPLJ5 and replace the failing clutch. You'll know you have enough tension when the mis-feeds stop.

    It is almost an unavoidable design problem for top-feed printers where users can grab the paper, and that's probably why you don't see them anymore. However, it is informative why ANY printer could mis-feed if the spring-wrap clutch is worn out.

    It is also a good practice to ALWAYS try to feed mis-feeds and paper jams forward along the paper path (and not jerk it out backwards).

    HP LaserJet 5 SIMM codes

    (From: David B. Gustavson (dbg@SCIzzL.com).)

    Here are the empirically determined SIMM codes for the HP LJ5: (o for open circuit, g for grounded jumper)

     Pin 70 69 68 67
    -----------------------------------------
         o  o  o  o  treated as an empty slot
         o  o  o  g  53.00.02 error
         o  o  g  o  53.00.02 error
         o  o  g  g  53.00.02 error
         o  g  o  o  53.14.03 error  
         o  g  o  g  16 Meg RAM
         o  g  g  o  2 Meg RAM (=LJ5 70ns)
         o  g  g  g  4 Meg RAM
         g  o  o  o  53.14.03 error  
         g  o  o  g  16 Meg RAM
         g  o  g  o  53.14.03 error
         g  o  g  g  4 Meg RAM (=LJ4 80ns)
         g  g  o  o  53.14.03 error  
         g  g  o  g  16 Meg RAM
         g  g  g  o  53.14.03 error
         g  g  g  g  4 Meg RAM
    

    Since there are several codes that have the same RAM size, it's possible that they correspond to different RAM speeds or other differences that might matter. I connected my $129 16MB 70ns 32-bit-wide 72 pin SIMM in the g o o g pattern, and so far it seems to work OK.

    If anyone has more info, such as speed or other characteristics that ought to match the ambiguous codes, I'd be very interested. Some of these codes correspond to the RAM/ROM PostScript SIMM, but those seem to be driven from a logic array and might have more complex behavior. In particular, no static code was interpreted as such a PS SIMM, but that might be because it already found one in another slot.

    With a duplexer, the LJ5M barely functioned with the original 6MB RAM, had to run it at 300 dpi or it would just not bother to duplex. Borrowing 4M from my old LJ4M raised it to 10M, which raised the performance ENORMOUSLY. 16M raises it to 22M, which is surely major overkill, but for $129+tax at Fry's, why go for less.

    So far the software on my Mac is refusing to control the duplexing features, e.g. the "which edge is the binding edge" choices are always disabled, but turning it on at the printer works (unselectively). But maybe this is due to some beta printing environment stuff I'm using.

    HP LaserJet random behavior - no ground

    Aside from surge supressors not being effective (to the extent that they ever are) without a proper safety/earth ground, here is another example of possible symptoms:

    (From: Leif Gastgivar (lgastgiv@technis.syh.fi).)

    I bought a new HP Laserjet 5L printer and I just plugged the printer into the socket. After a time the printer started to print out pages by its own. I checked out the manual but I couldn't find out the problem. But after a wile I find out, that the printer wasn't connected to the ground. After I fixed the problem, it will have been working properly.

    Determining if HP LaserJet partial print problems are scanning or logic

    This would apply if, for example, an HP-LJ3 prints only left side of the page.

    If the boundary is sharp and constant, logic is likely but not always.

    If the boundary is fuzzy and/or ragged, blockage in the optical path is more likely - a label or Post-It(tm) note that escaped, or even a wad of dust or other debris.

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    Does the printer have an 'Engine Test' switch (a button on the DC controller PCB on the LaserJet 2, and one on the side of the LaserJet 1)?

    This will cause it to print a test page (of vertical lines normally) even if the formatter board (the thing that translates the incoming data into a bit stream to send to the laser) is defective.

    If you can find such a button (it's hidden on the side of the lower cover on the Laserjet 2), press it and see what happens. If you only get half a page, then the fault is almost certainly optical (Check for defective mirrors, etc as mentioned earlier in this thread). If you get an entire page of lines, then the fault is in the formatter board. I have no info at all on any formatters other than the Apple Laserwriter 2NT one, alas

    (From: Ralph Wade Phillips (ralphp@gcstation.net).)

    On one side of the bottom, there's a cover that can be removed after removing one screw. After that, the button is visible through a hole.

    Only push this AFTER it warms up all the way - it's ignored until the engine is ready!

    LaserJet IIID and others: paper not picked up correctly

    "The printer will print perfectly on both sides if the paper is fed into the sheet feeder. If the paper is fed from either of the paper cassettes, the paper not picked up from the cassette. There is a mark on the paper where it appears the roller has been rubbing on the paper."

    (From: Al Savage (asavage@iname.com).)

    Piece of cake. Replace the pickup rollers. You can clean them, but it won't last.

    Now, the bad news: it's not real easy. Or, like most things, it's really easy once you've done it a couple of dozen times.

    The rollers themselves are about $5 these days, and have been redesigned to eliminate one problem they used to have: you can't put them on backwards anymore!

    LaserJet IIID: remove all exterior plastic: three screws up top accessed after opening the lid. One screw horizontally near AC power cord receptacle. Release nasty catch of top lid from side plastic at just above AC receptacle. Try hard not to break top lid while doing this. :)

    Now you can access two screws retaining front edge of side panels to front panel. Remove two vertical screws holding left side panel to rear of printer chassis, near fuser.

    Unhook front panel operator panel cable, remove front panel assy.

    Remove six small screws retaining front chassis subframe to (scanner, HVPS, DC PS), plus about five larger screws holding power envelope feeder subframe to front.

    Remove DCPS on right front of chassis: remove three vertical large screws (two in front, one at right rear). Disconnect main motor harness from DCPS. Disconnect gray fibre optic cable from black clip at left front edge of DCPS, or it will be damaged, and you'll add another large batch of screws to remove/replace! Then remove DCPS by grasping firmly and pulling straight up. This takes considerable force, as there are connectors at the bottom that you are separating.

    I recommend removing the registration assy prior to removing the paper pickup assy, but it can be done without. To remove the registration assembly, remove four vertical screws (three black, one chrome, most likely on III series) from reg assy, which is the part with the green "handle" just inside the paper path, as you look straight down into the printer. The left rear (shiny) screw will likely have a short ground wire under it on a III. With the DCPS out, the reg assy will just lift straight out. Note carefully the bronze ground lug at the left front of the reg. assy. It must be rotated forward at reassembly or the forward black roller (small diameter, 9" long) on the reg assy won't be grounded, and you'll get all kinds of odd print quality problems. Look at it now, BEFORE removing the reg assy, to see how it's supposed to look.

    Using long #2 Phillips, remove two small screws retaining the pickup assy (the shaft with the grey PU roller on it, plus the black or white spring clutch on the right end of the shaft) black plastic bearing blocks. Lift up PU assy, slide 2" to right (the reason you had to remove the DCPS), then swing left end rearward to where the reg assy used to be, and remove.

    To replace the PU roll: remove E clip on left end of shaft, slide off all the washers, spacers, etc, noting the order carefully. Roll just falls off!

    On reassembly, don't forget to reconnect the main motor's wire harness to the DSPS. One of my common problems.

    If you're going to do the lower PU roll, do it now, prior to reassembling the top half. Remove the lower side plastic panels -- one horizontal screw in back for each side.

    After removing the sides, remove the E clip on the left side of the lower pickup assy, then remove the bronze shaft bushing. Don't lose it.

    On the right side, remove the three small horizontal screws on the clutch plate, disconnect the clutch's harness from the chassis harness and harness hold-down clip, then rotate the clutch plate and slide the lower PU assy out the right side.

    Replacing the PU roll is identical to doing the top one at this point.

    Now you know why I charge 1.5 hours to do top & bottom rolls. Plus, I pull the lower pan and vacuum it out, Fedron the reg assy, and replace upper/lower fans if needed.

    The IIID is the best laser printer HP ever made, barring the Si series. Well worth the effort and expense, even if you have to replace the fuser too. I like them a lot.

    Done right, a proper PM of a IID or IIID involves removing the upper unit from the lower to properly clean the skewed feed roller, but that's another 30 minutes, plus cleaning the refeed assy. You can "kinda" clean that lower feed roller (not the PU roller) if you have small hands and a long Q-tip, but it really isn't a good job.

    PS: oh, yeah. I wrote this all from memory, and I haven't done one in a couple of weeks, so I just *might* have overlooked something. But the major steps are there. Keep track of the various screws, they're not all interchangeable.

    Laserwriter LS

    "I have a Personal Laserwriter LS; am getting 'fuser assembly malfunction' error. Does anyone have experience w/this, know the likelihood that I need to replace the entire fuser assembly, or how I can find out? Also, is there a place to get a used assembly, and is it difficult to make the repair myself? Stores charge $200 parts and labor for the replacement, and this printer's not worth that investment."

    (From: Frank Reid (reid@indiana.edu).)

    The fuser lamp often fails in that model. The replacement is Apple part number 890-0427. I think it costs roughly $25.

    Apple technical information

    The following Web site provides links and a search capability for Apple computer products including Apple printers:

    Apple Lserwriter I/O

    "I just picked up an Apple Laserwriter II NTX which appears to be working. The problem is I need to find out what this thing has for I/O, and what the dip switch settings are. It appears to have a 50 pin centronics connector, along with a DB25, an appletalk port and one other port."

    (From: Erik Johansson (erijo105@student.liu.se).)

    The ports are a Phonenet Appletalk connector, a 50 pin centronics-like scsi connector (to connect a font cache hard disk), 25 pin female D-sub serial connector (wired as a DTE so the cable should be the same as when connecting to computers, not a computer and a modem) and a RS-422 8 pin miniDIN connector (also for serial communication).

    The jumper settings:

     Switch1 Switch2           Function
    ---------------------------------------------------------
       Up      Up     8 pin AppleTalk (Serial Port Disabled) 
    
      Down     Up     25 pin RS-232 and 8 pin RS-422 
                      Serial Ports 1200 baud 
    
       Up     Down    25 pin RS-232 and 8 pin RS-422 *
                      Serial Ports 9600 baud 
    
      Down    Down    25 pin RS-232 serial port 9600 baud;**
                      pin RS-422 serial port 0 baud 
    
     Switch3 Switch4   Function
    -----------------------------------------
      Up       Up     PostScript Batch 
      Down     Up     Diablo 630 
      Down    Down    HP LaserJet 
      Up      Down    PostScript Interactive 
    
     Switch5 Switch6   Function 
    ----------------------------------------
      Down    Down    No Handshake 
      Up      Up      ON/XOFF 
      Down    Up      Etx/Ack 
      Up      Down    DSR 
    

    Apple LaserWriter and LaserWriter Plus paper jams

    (From: Ralph Wade Phillips" (ralphp@techie.com).)

    I suggest that you cruise on over to The Printer Works and check out the blowup parts list for the LaserWriter and LaserWriter Plus mechanical (Canon CX engine - also LaserJet, LaserJet 500, LaserJet Plus, and several, SEVERAL other printers). That will make the text easier to follow. (Use the search facility for the printer model - that will include the "Parts Identification Diagrams".)

    To repair the MOST common problem with consistent jams at the paper INLET, you have to strip the printer down to where you can remove the Registration Shutter Assembly. Due to how the LaserWriter I/O board is connected, you'll have to remove the I/O board (the big one with the Plus ROMS on it), and the case it's in (Note: DISCONNECT the board from the computer's wiring harness, do NOT try to remove it from the case. The case should come off also - leave it mounted there.) After that, you can see the registration shutter mounting screws, along with the wiring harness for the shutter solenoid AND for the cartridge installed/sensitivity microswitches. Remove the shutter assembly. You'll have to either dismantle it and clean the solenoid out, quite possibly having to replace the rubber bumpers, or you'll have to replace it.

    I have left out the most obvious steps of removing the upper housing and several other steps - they should be obvious from the parts diagrams for the printer.

    Apple LaserWriter prints double/repeated images

    The characteristic is faint repeated printing a couple of inches down the page as well as from the previous page.

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    On a Laserwriter 2 series (the most common one IMHO):

    With the top cover open, look for 2 ping contacts in a little white pillar attached to the cover on the left-hand side. When the cover it closed, it makes contact with 2 similar contacts on the PCB on the left side of the fuser. Check for continuity (but not 0 resistance) between the 2 contacts _on the cover_. If it tests O/C, remove the toner cartridge (you did that, right?), then the little metal plate (grey metal, held on by 1 screw) behind it, then undo the 2 terminal screws under this, undo 2 more screws on the large grey metal assembly, and remove it. Inside this are 5 bulbs in series, one of which has probably blown. You can get replacements from the PrinterWorks

    If those bulbs are OK, then check the power transistor on the PCB on the left end of the fuser.

    Apple LaserWriter IIg runaway scanner never stops

    (From: Dave Lee (leedj@uwec.edu).)

    A good possibility is the cable from the scanner to the DC controller. It might just need to be re-seated. Might need replacing.

    Apple Laserwriter IINT error codes

    "Where can I find the meaning of the flashing error codes on a Laserwriter II NT printer? It is flashing both the paper jam and the paper out light. The fuser doesn't heat up."

    (From: Ralph Wade Phillips (ralphp@gcstation.net).)

    It means that the fuser isn't getting to proper heat. This might be a blown fuser, might be a bad AC Input Block, might be a bad DC controller.

    Before I fought TOO hard, I would pull the fuser assembly and check the 115 VAC inputs for continuity. If you don't have any, then I'd say you most likely have an open fuser lamp, and it will need to be replaced.

    If you have continuity, I'd change out the AC Input Block, and work from there.

    The DC controller being dead is rare, but it *can* cause the same symptoms.

    (From: Mark Wolfe (markw@wwa.com).)

    Do what the other guy said, but instead of replacing the AC Power Block, check the triac at Q101 inside the ac power block. Common failure on this engine. When you do fix it, put a good heat sink on the thing.

    Apple Laserwriter IINT 'clicks' with intermittent fuser error

    "I have a LaserWriter IINT with an intermittent fuser error. When the printer is switched on, sometimes it cycles normally and works fine; but sometimes, the startup cycle sound is followed by a soft click, and a few moments later the green light gives way to double blinking red. I have attached a voltmeter to the fuser lamp contacts; when the soft click is heard, no voltage reaches the fuser."

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    The click is almost certainly the fuser protection relay dropping out. This relay is located in the AC input block assembly at one end of the fuser, under the main cooling fan.

    This relay is on the lower board in that module, and is driven by the protection circuit (a few transistors, not hard to trace out if needed) on the upper board. It operates if the fuser drive signal from the DC controller is active for too long at a time - it prevents the fuser from overheating if one of the CPUs on the DC controller goes crazy

    OK, things to check:

    1. Look for dry joints on both boards in the AC input block. They are *very* common here.

    2. Check the thermistor in the fuser. Clean it, check for dry joints, check that it is pressing against the fuser roller.

    3. Reseat all the connectors on the DC controller board associated with the fuser and AC input block.

    4. If that doesn't cure it, you'll need to hang a scope off the fuser drive signal (one of the 4 wires from the DC controller to the AC block - the other 3 are ground, +24 V and fan speed control) and see if the fault is in the DC controller (Signal does stick high) or the AC block.

    Diagnosing a blank vertical strip problem on Apple Laserwriter IINT

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    There aren't many (if any) electronics faults that can cause this, thankfully...

    First press the test button on the side of the bottom casing round the back. Does the test printout also have this strip missing? If not, then you've got a very strange problem with the formatter board, and I'll have to think again...

    Secondly, take out the cartridge and shake it, and put it back in. If that doesn't help, then try a new toner cartridge.

    If you've still got problems, then the most likely problem is something in the beam. SX engines (which you have, and CX engines and...) print black where the drum is discharged by the laser [1]. Start by removing the toner cartridge. There's a black metal strip in the top cover above the toner cartridge. By fiddling with it you can move it slightly, exposing a front-silvered mirror. Inspect that for bits of paper, etc. Clean it _very_ carefully.

    Next area to look at is the laser scanner itself. If you know what you are doing, take off the outer casing (screws round the outside, some under the lip that the lid closes onto, and 2 on a metal bracket at the left side of the fuser) and look at the scanner block. This is the black thing mounted over the paper tray. Unplug the cables (one to the laser PCB itself, one to the scanner motor under the little flap on top), undo the small screw to release the optical fiber, and undo the 4 screws that hold the scanner in place. Lift it out. Look at the slot on the front edge for any paper, etc. I don't know if I recommend you opening the scanner (Canon DO NOT, but I've done it), but you can carefully trim back the heat-moulded studs and open the cover. Look for debris inside. Handle it with great care, of course.

    (From: Ken Eckert (eckert@sfu.ca).)

    One problem that gives this printout is loose screws on a plate in the top cover above the toner cartridge. The screw(s) fall out and get stuck in the toner shutter window that that the laser goes through. I've had a couple like that, I made it a habit to tighten those screws whenever I work on one of these Canon engines.

    Upgrading Apple LaserWriter to LaserWriter Plus

    It may be possible to upgrade your Apple LaserWriter if you have a partially dead LaserWriter Plus.

    (From: Ralph Wade Phillips" (ralphp@techie.com).)

    There are two ways. One is to swap the eight or sixteen ROMS from the Plus into the same sockets on the LaserWriter, !AND! to swap the programming shunt assembly ( a set of four jumpers in a 16 or 24 pin DIP socket), placing it in the exact SAME place. The easier way, if you have both printers, would be to remove the upper cage and swap THAT. This will mess up the page count, however, that's not such a big deal nowadays (not on a CX engine - after all, does it REALLY matter on a '88 Dodge Aries K that it's got 213K miles or 127K miles? ... )

    Toner All Over Paper on Various Brother Laser Printers

    (From: Robert Wilson (rfwilson@intergate.ca).)

    Both my 300 dpi Brother 641 (sold as the 630 in the USA), and my friend's 600 dpi version of the same printer, had a problem where toner ended up all over the page. What a mess.

    The problem was that there is a long thin spring that is rotated at one end, and propels the used toner (scraped off the drum) back to the point where toner enters from the toner container. It acts like an Archemedes' Screw, gradually transporting used toner back again for reuse. It also transports fibers of paper that have been scraped off, and therein lies the problem. Brother stupidly "closed" the end of the long spring (its last coil is bent to be in contact with the coil before). The result is that paper fibers (once they reach the end of the spring), get caught in the closed end of the spring and cannot get out.

    The fibers build up until they jam the end of the spring and it can no longer rotate. The drive mechanism doesn't know this, and keeps rotating the spring until it breaks (usually right at the driven end).

    The solution is to disassemble the printer drum (not all that hard, but not for the faint of heart!), remove the spring (it's about 15 inches long), and bend the end so it engages into the drive gear again. Then, eliminate the original problem by opening the last coil at the far end, so fibers can get out.

    Resetting "REPL.DRUM" error on Sharp JX-9460

    This will probably work for other laser printers as well though the details may vary. Use at your own risk!

    (From Owen Solberg (osolberg@infinex.com).)

    If your Sharp JX-9460 laser printer has decided it is time to give you the "REPL.DRUM" message on the LCD screen, but the print quality is still fine, then all you need to do is fool the page counter to think a new drum has been put in. Here's how:

    1. Open the cover and remove the photo-drum.

    2. Look down into the area under where the drum was. On the right hand side, you will see two circular metal contacts. You will also see two "slots" on the far right side. These slots mesh with plastic tabs on the drum cartridge.

    3. At this point you will need two paper clips. Use the first one (unbent) to insert into the FORWARD-MOST slot. You don't have to push it very far. You will hear a click and the LCD panel will probably go from saying "COVER OPEN" to saying "REPL.DRUM." Keep holding the paper clip in the slot while you:

    4. Touch the 2 ends of another paper clip BRIEFLY to the two circular metal contacts. (you will have to unbend the paper clip a little.) It will spark a little. Don't worry, it is only 4 volts. But I wouldn't hold it there for too long.

    Anyway, the theory behind this is that the new cartridge comes with a fuse in it which is blown by the 4 volts the first time you insert the cartridge. That is what resets the counter. Better than spending $190 on a new drum, right?

    TI MicroLaser Plus laser printer reports 'Main Motor Err'

    "I have a Texas Instruments Microlaser Plus laser printer which after I turn it on, reports that the self-test passed but then displays an error on the LCD: 'Main Motor Err'.

    This laser printer uses the Sharp JX9500 engine and I was able to find out how to get it into diagnostics mode. I selected "Test Print" and it returned "Service (C2) 01". The stepper motor appeared to be working correctly along with the fuser lamp."

    (From: All Laser Service (laser@ix.netcom.com).)

    The lubricant used on the gear train tends to gum up and the motor strains to the point that you receive a main motor error. Take the complete gear train apart and clean it. You will need to disassemble all the gears and clean both the gears and the axles. Also take a look at the developer and drum cartridges as they are driven by this gear train. If they are jammed this will also cause your problem.

    Fuser problem/printer parts

    (From: Robert Blackshaw (blckshaw@clark.net).)

    "I have a ti-microlaser printer that worked great until a gear in the fuser assembly cracked. This gear drives the rollers in the fuser. If anyone can tell me if there is a place to get used parts or a kit of the common parts that fail in the fuser etc. it would be a great help. Also looking for any other info on this printer such as: schematic, user manual, and part numbers for the photoconductor unit, developer unit and toner cartridges."

    Try The Printer Works at http://www.printerworks.com.

    I fixed an HP Laserwriter II (same engine as the NT) with exactly the same problem, a $0.49 gear on the fuser assembly. On top of it all their catalogs are like service manuals with exploded diagrams of everything.

    Swapping fuser parts

    "I have a couple of Scrap Brother HL-8 Laser printers.

    Both have defects in the Toner Fixing unit (Fuser roller?). Which is the unit that melts the toner onto the paper.

    One unit has VERY BAD scratches on the Toner fix roller itself, which causes a bad streak on pages.

    On the other unit the heating element on the Toner fixer has blown. The big question is can I take the heater from one, and place it in the roller of the other? Anyone done this? A new roller unit will cost me 90 quid, so a couple of hours to actually do it is worthwhile, as a working laser printer will be the result."

    (From: JStev55598 (jstev55598@aol.com).)

    No problem if you are careful when swapping over the fuser lamp you will have a working printer which is a darn site cheaper than a re-con unit. One thing to bare in mind is what made the lamp fail in the first place. Although it has usually got to the end of it's natural life sometimes a failure in the temperature sensor or a power supply fault can cause the lamp to overheat.

    When turning it on for the first time after replacing the lamp check that it switches on and off after it's initial warm up . You can sometimes see the lamp when it is on through a vent in the side of the printer by the end of the fuser roller.

    Panasonic KX-P4410 CHNG DRUM error code 027

    (From: David Moisan (dmoisan@shore.net).)

    The drum sensor on my 5400 is an opto-interrupter that sits over an opaque flag that's connected to a bucket inside the waste-toner compartment on the drum. When the bucket is full, the flag blocks the sensor and causes the CHNG DRUM indication.

    Carefully drill a hole to get the toner out and BE CAREFUL OF THE DRUM SURFACE. I killed mine doing this. What sucks is that when this happened I was getting the indication and I only had 4400 pages on it (it's a 6000 page life span, supposedly).

    when you're done, power up the printer while depressing ENTER. The display should tell you "DRUM COUNTER RESET" or something like that. Another fun thing I really love about the printer is how the developer mechanism--the magnetic drum that picks up toner--is permanently mounted in the printer. Lots of fun if the scraper is removing toner in one spot and you can't clean it. :( (A slip of paper *somewhat* works.) I only found this out after tearing my printer down *completely* and removing every last bit of old toner.

    After 3 years, I'm *not* happy with my printer any longer. Though it's had a new drum, it has *never* worked the same since it was changed out. White streaks on the output where there's not enough toner. And smeared characters where there's *too* much toner. *sigh*

    It goes against our dogma here to say this, but I am very tempted to throw my printer out the window. (And I say this as a Panasonic owner who loves his 27-inch TV.) It's not repairable, I'm tired of tearing down the printer for a fault I can't possibly fix. And I'm tired of blowing another $70 on a drum that will die before I know it. Not when I can get a new printer for about the same price, 600 DPI and at least 12,000 pages before I have to spend big bucks on a drum. Like Curly Sue, when it was good it was very very good but when it's bad....

    Panasonic 4420 laser printer error code E31 and other comments

    (From: Al Savage (asavage@iname.com).)

    E31 is the most common reason for a 4420 to fail.

    The manual says that 'fusing unit failed to reach x degrees in 90 seconds' or words to that effect. Makes you think of fuser problems, right? Bulb, thermal fuse, thermistor? Well, only about 1 out of 10 times.

    The problem is solder blown off two pins in the AC power supply, located on the front left side of the printer (after removing plastic cover) as you face the front. Easy fix, if you're moderately handy.

    E31 and dirty feed rollers (and paper pickup roller) are about the only things that fail on a 4420. Well, you do need to replace the developer and drum every so often, and they're pretty expensive, but they're long-lived, too. Much lower cost-per-page than any HP product.

    I happen to think the 4420 was Panasonic's best-made laser printer. The 4450 is over twice as fast, at 11 pages/minute, but you can't really run laser label through it. And it's MUCH harder to service.

    Copy counter fuses

    "I have a Panasonic KX-P4420 laser printer. It locked up with a message about 36K service.

    I issued the incantation to reset this message. It now works again, but the display is flashing 'Change DEV' and 'Change Drum'. This makes it more difficult to use the menu system. I'd like to turn them off.

    From the dealer's explanation, I gather that there are fuses in both the developer and the drum. When you install a new one, the machine senses the fuse, resets the counter then blows the fuse. If this is true, I should be able to bridge the fuses with another and reset the counters. Maybe even a resistor will do it. Or maybe even a reset switch somewhere?

    Can anyone tell me how to reset the error messages for the developer and the drum? I'm willing to disassemble the thing to do this."

    (From: Jeff Roberts ( jroberts@axionet.com).)

  • To turn off change drum message turn machine on while depressing "<" key

  • To turn off change dev message turn on machine while depressing "^" key

    (From: Mark Wilson (mawilson@worldnet.att.net).)

    There must be something additional to that. I tried it on my 4420 and it did not work. Can anyone shed additional light on this??

    (From: Jeff Wilkinson (laser@ix.netcom.com).)

    The fuse on the drum unit burns out when you first install it. This momentarily shorts the input to a counter IC and resets the counter. I would be very careful about shorting it with a piece of wire, even though the circuit is current limited it is just not a safe practice. Of course you could always replace the drum! The same is true for the developer unit. The developer and drum unit should have been replaced at both 18K and 36K pages as they have reached there useful life expectancy. E-mail me if you want more info, I believe I have the value of the fuse required here someplace.

    (From: Mark Wilson (mawilson@worldnet.att.net).)

    I believe there is a module with a microfuse, similar to the one on the toner cartridge. If this is so, you have to replace the microfuse (preferred) or short it with a piece of wire (not recommended). The fuse burns out after so many pages, triggering the drum message. When the drum is replaced, it has a new (intact) fuse.

    Laser Printer info

    "Is there any info available on the net on how Laser Printers work, & how to fix them? I've worked on a few, & am learning the hard way, but could use all the help I can get."

    (From: Robert Blackshaw (blckshaw@clark.net).)

    Lotsa luck! I have an HP LaserJet 500+, an Apple Lasewriter Plus, and a Xante AcceleWriter which were DOA and which all now see active duty. The only piece of information that I have that is very useful is the HP Printer Service Manual P/N 02686-90920 that I got *after* solving the LaserWriter Plus' problems.

    I went through Border's Books and other computer book shops looking for anything covering laser printer internals with no luck at all. It's your brain and logic, and luck.

    One thing that will cause you grief on the older CX engine based printers are those *insulation displacement* connectors they used. Occasional no contact problems are usually solved by pressing the wires into the plug.

    Strange running time meter/copy counter

    "I have disassembled (read: cannibalized for parts) an old Cannon laser printer a few months back. I found a mysterious part in it. Perhaps somebody can enlighten me as to what it was thrown in for...

    It looks just like a standard fuse, as found in power supplies. The usually-glass part is made of white plastic. There is a window on one side, made of a clear material(glass, plastic?) And there is a scale next to the window, 0 to 10.

    In the window is some substance that looks like mercury from end to end, but there is a "break" somewhere in the middle (around 3 or 4 on the scale)."

    (From: Tony Duell (ard@p850ug1.demon.co.uk).).

    The substance is mercury, AFAIK, and in the 'gap' there's a small amount of some electrolyte. Passing current (very low current) through the device electroplates mercury from one column to the other, thus making the gap appear to move along the tube.

    It can be used in 2 ways - if a constant current is passed through it, it records the total time that the unit has been in use. That is the more normal way to use it.

    However, in the CX, it's fed with a short pulse of current at the start of each page. Thus, a small amount of mercury is transferred for each page printed, and the device does, indeed, operate as a page counter.

    Laser Printer prints heavy on one line about 2 inches from bottom

    "What could be causing my Brother HL8e laser printer to smear/or blur one line of text about 1-2" from the bottom of the page. At this point, 90% of the page has already fed through the printer with no problem. Can't see any botched labels or other obstructions. It doesn't always do it, but at least 50% of the time if there is text at that point on the page, there will be a heavier print on that line. I don't know if you would call it blurring, it's kind of like it's printing twice double at that point. Is it the rollers? Which rollers should I replace?"

    (From: Frank Reid (reid@indiana.edu).)

    If changing the toner cartridge doesn't fix it, the lower (rubber) fuser roller may be bad. Those (at least in HP printers) sometimes don't pinch the paper tightly enough during fusing, causing smears.

    The fuser has a teflon-coated hollow metal roller with a heat lamp inside, and another roller which pinches the paper against the hot roller during fusing. The lower roller is made of high-temperature silicone rubber. Those sometimes go bad as described above, but if you have replaced the whole fuser assembly recently, it probably isn't the problem.

    Look for any rollers between the pickup roller and the fuser, and clean them with naphtha or mineral spirits. If there is a black roller with foam-like surface, that one is electrically conductive and is part of the mechanism that places electrical charge on the paper. Clean it with alcohol and do not get fingerprints on it. Clean everything in the paper path: If there is a corona wire (instead of the conductive roller), clean it with a Q-tip dipped in alcohol.

    Image tilted/skewed/crooked on old IBM laser printer

    "I have an ancient IBM Laserprinter E P/N 1039229 that has an aggravating problem: the printer prints fine except that the image is skewed on the page. There are no problems with the image itself other than the fact that it is a little crooked. I suspect that the take up wheel (D-shaped with rubber coating) is the culprit because the paper does not jam. Anyone have any experience with this? I don't want to replace the wrong part!"

    Bad rubber is a very likely possibility. There are rubber restorer chemicals - don't know how well they would work. Sanding the top layer may help. Replacement would be best if you can locate parts.

    Fuser Roller collects toner on laser printer

    "I have an AST TurboLaser/PS (also known as an DEC LN03, a Brother, etc, etc.). When I bought it someone had let a ring of melted toner collect on the fuser roller until it had burnt through the coating and ruined the roller. So I replaced it and ran a few thousand copies through the printer. Now I notice that the roller is beginning to collect a bit of toner again. Just how does someone clean that roller without pulling the coating off? I tried the usual wiping with a paper towel and that removed some of it but there is still a hint of it left and a few more copies begins to let it accumulate again."

    (From: FAXFIXR (justdfax@cdepot.net).)

    I would bet the "picker fingers" or "separation claws" are in need of replacing. They are the claw type pieces that ride on the roller and prevent paper from sticking to the roller. The end that rides on the roller will build up a coating of toner and crud and will wear a groove thru the teflon coating of the roller. Once the teflon coating is gone, toner builds up in the groove and shows up on each page as a faint line.

    HP original laser printer 2686A: bargain or boat anchor?

    "This printer is (i'm told) supposed to print a test page full of assorted characters yet only prints multiple parallel lines. Also, i'm unsure of the proper hookup to Win95, parallel or serial interface. To clarify, I bought this thing used from someone who 'knew nothing about it' and the HP web site volunteers little information."

    (From: Gerald Chafee (GChafee@worldnet.att.net>).)

    If I remember right the original Laserjet has a "test switch" located towards the back that only tests the print engine and is supposed to only print parallel lines. I think that you can take the printer off-line from the front panel and get some sort of printout by holding down a self-test switch on the front or a combination of switches. Somewhere I have a service manual for this unit and I will try to look it up.

    BTW, the LJ I's were invariably a serial port only printer which made them a pain to interface. They do give a good print for such old technology, but you only have 1 or 2 resident fonts and I believe there was no graphics capability. You had to use cartridges to get any other fonts.

    (From: Mike B. (osiris@avana.net).)

    It's printing correctly. If I remember, there are two ways of testing this thing. You are hitting the 'test print' button on the side. This is the parallel lines test. There is another test button on the front panel that when hit, causes the cascading alphanumeric printing sequence.

    With Win95, you should be able to use the HP Laserjet driver with no problems. Since you have Model #2686A, I think the 'A' stands for parallel connection. In that case, just connect it like any other parallel printer, and make sure that you have the proper Win95 drivers.

    Why doesn't the HP site help much? :-). They just want to sell you one of their new, whiz-bang models :0

    This printer is a great workhorse. I believe you will still find lots of support for it from other places. There is a place called Laser Connection that supports/services these printers.

    Okidata printer that's streaking

    (From: Dan Fraser (dmfraser@rogers.wave.ca).)

    These printers need a new drum every 4-5 toner refills. They are designed that way to fool you into buying them as the toner is cheap. Then they get you later at drum time. The drum is a consumable and does NOT last the life of the printer. Resign yourself to a new drum every 4-5 toners or so. That's the system.

    (From: Chris Laudan (chris.laudan@zetnet.co.uk).)

    Yup, agree with this. The cleaner unit has a fine clear plastic strip that removes old toner from a roller, in time this develops fine kinks or scratches which let old toner stay on roller, hence streaks. If this strip is OK and machine says need new cleaner unit, you *can* carefully empty cleaner unit and carry on, but you must be careful not to damage strip doing this. Best to replace unit as above,

    First page smudges on OKI OL400

    "Sounds like my second hand (sorry, previously owned) OKI OL400 has a problem with the fuser roller, too. Up till now I've just printed two first page copies of everything I needed 'clean'.

    Please does anyone know if the fuser roller is an integral part of the OKI OL400/800 Image Drum Cartridge replacement kit? If not, any ideas on the part number, please?"

    (From: Al Savage (asavage@iname.com).)

    Note that an OL400 is nothing like an OL400e. Almost no parts interchange including the drum/developer assemblies.

    (From: Brian Hughes (bkhughes@gisco.net).)

    The problem you're both describing is caused by the "wiper blade" in the drum cartridge, not the fuser! OKI doesn't sell the part and says when you have this problem you must replace the entire image drum assembly $$$$

    The cure is really quite simple: I remove the entire drum cartridge and place it on newspaper under subdued lighting (you don't want to "shock" the drum). The corona wire assembly can be recognized by the sliding blue knob on top; I release the left side with a small screwdriver tip and remove it. After removing the two screws I have just uncovered, I lift the blade free. Gently wiping the accumulated toner off the blade allows me to see the rubber better. If I see that the blade has "curl", I can then weight it down on my bench for a while to reverse the curl before I reassemble it. Sometimes all it takes is the cleaning. I have done this with my own "preowned" OL400, and now enjoy like-new printing.

    The one that stumps me is where to find a fuser lamp, OKI will only sell the fuser assembly (major part!).

    DISCLAIMER: Due to the possible health hazards of toner dust, I have only told you what I have done...it is your choice, and your responsibility to take precautions should you disassemble your printer.

    (From: George Hurley (ghurley@voicenet.com).)

    That smudge on the first page is your OL400 telling you that your image drum is getting old - they're about $240 from Staples, or $180 rebuilt. HOWEVER, the actual cause of the smudge is the failure of the toner wiper blade inside the image drum assembly. This acts like a windshield wiper and scrapes excess toner off the drum. When it hardens with age, it stops working as well as it should. This blade can be replaced at fairly low cost - I bought one for $25 and suspect that I overpaid, and it took about ten minutes to replace the old one. You'll eventually need a new drum assembly, but this repair should squeeze another 10-15,000 pages out of the drum.

    I forget who I bought the blade from, but LaserImpact should have one. You can reach them at 1-888-809-4155 - if you ask for tech support, they can probably give you instructions on how to do it.

    Resetting 'Replace Drum' message on OKI OL400

    The following may apply if the printer produces quality output but insists on the error message. Of course, if the printouts are faded, etc., it may indeed be time for proper maintenance.

    (From: Jason Kuetemann (jason.tracey@sympatico.ca).)

    Press the 'RECOVER/RESET' button while turning the printer ON. This will reset the counter.

    (From: Steve TR I have this model, too. Don't fall for that drum error. It only goes by a page count and the drum will continue to yield quality images for at least another 200-500 pages! Also, you can hold down the MENU 1 key to get into a service menu where you can reset the drum count and total page count for the printer.

    Laser printer test equipment

    At least one company offers a device specifically for testing of laser printers. This is obviously not going to be something you will want if you deal with 1 laser printer every few months. However, where dozens of printers a week are involved, check out: http://www.LaserWizard.com/.

    Frank's repair notes: HP-IIP, HP-IIIP, Apple Personal Laser Writer

    (From: Frank Reid (reid@indiana.edu).)

    All of these use the same Canon print-engine.

    Tony's entry into laser printer repair

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    You may be interested to know how I got into laser printer repair. It's a long story, but here goes...

    I was given a non-working Canon LBP8A1. I pulled the case and started fiddling about and discovered a PAL on the formatter board with a stuck output. The cure was obvious -- replace the PAL.

    Alas Canon didn't like that solution. No parts were available, and no manuals. At about this time I discovered that the original printer for a computer that I happen to love - the PERQ - was a CX-VDO -- the same printer without the formatter. And I managed to obtain the PERQ interface board, admittedly non-working.

    So I totally dismantled the printer in the hope that I could figure it all out. I had a pile of screws, gears, lenses, mirrors, bearings, etc. And PCBs covered in unidentifiable chips.

    A lot of work with data books (and questions to newsgroups) identified most of the chips. A lot of hacking about got me enough of the pinout of the CX DC controller connector to guess roughly what was going on.

    Then I had some luck. The guy who'd given me the PERQ card remembered that the CX-VDO had a ribbon cable from that connector to the outside world. And Bob Davis, who had obtained all sorts of stuff when PERQ Systems folded, dismantled his personal machine and ohmed out cables, etc.

    Slowly it all went back together. I figured out how to align the scanner unit using the IR detector I use for testing remote controls. I figured out how to test (and repair - there was a defective chip and a shorted capacitor) the main PSU. And I worked out how the status LEDs were connected.

    I made up what I thought were the right cables, put it all together and fired it up. The test page was fine. I was getting there. Put the PERQ card together, plugged it all it. It sort-of worked. The page was black apart from a 16 pixel strip at the left. But Bob had been helpful and had sent me info on the operation of this card. I was my fault. I'd missed out a jumper which connected a clock to the data FIFO. After that it worked fine.

    I now believe that these printers *can* be repaired at home, no matter what Canon say. And if Canon won't help people, then somebody else should...

    Repairing plastic paper feed strip in Canon PC10, etc. or CX laserprinters

    (From: Curtiss Priest (BMSLIB@MIT.EDU).)

    Serach at: Google Groups for the subject heading: "Repairing plastic paper feed strip in Canon PC10, etc. or CX laserprinters".



  • Back to Printer/Copier/Fax Repair FAQ Table of Contents.

    Photocopiers

    Note: also see the chapter on Laser Printers as the operation and problems of the two types of equipment are very similar.

    Warnings about vacuuming copier toner

    "I know there are special vacuum cleaners for use in picking up toner in laser printers. What is the problem with using a cheap ordinary vacuum cleaner? Is there a fire hazard? Thanks for any comments."

    (From: (jollyrgr@mc.net).

    If you vacuum toner with an ordinary vacuum, a static charge from the toner will build up in the vacuum and shock you. Toner works by static charge. Moving it, as in vacuuming, causes it to give up its charge to the vacuum. Without having a complete ground throughout the entire vacuum can cause charge to build up to quite a high potential. Be safe, use a toner vacuum.

    Now if the paper does not get fused, the toner can be rubbed off. This toner, and any spilled toner still retains some charge. As it is moved though an ordinary vacuum, charge is transfered to the various parts of the vacuum. (Much in the same way charge is transfered to a person walking across a carpet in dry weather). When the charge builds up, it has to find a way to ground. In the case of the person walking across the room, the charge is discharged when they touch a metal object such as a light switch cover or door knob. In the case of the vacuum, its the vacuum that builds up the charge. When the person using the vacuum touches the charged portion, the charge is transfered to them (ZAP!!). If the person is holding the part of the vacuum that is getting charged, they get charged as well. Only now they get zapped when they touch something else. A friend of mine worked in a print shop at one time. He spilled a bottle of toner. Instead of getting the toner vacuum used on the copy machines, he used an ordinary shop vac. The metal pipe was attached to a rubber hose. As he vacuumed the toner it was he that got charged. It was when he touched the grounded portion of the vacuum as he was turning it of that he got shocked.

    Toner vacuums have all their parts grounded (pipe, hose, canister, motor ect.). These parts are all connected by wires to the ground terminal on the power cord, shunting any built up charge immediately to ground. So it is not the conduction of the toner to the electrical ac line but from the charge the toner itself has.

    (From: jlager@tir.com).

    I don't know about any fire hazard, but I DO know what that stuff will do to an ordinary vacuum cleaner from lessons well learned! Toner/Developer is the finest stuff you may ever see, and will instantly clog all the pores of a regular vacuum bag. You'll go broke just buying bags. And... don't wash any of your clothes/rags with hot water that it has penetrated because it will make the stuff solidify. All my advice is based on repairing copiers over the years.

    (From: Ed Wright (motogump@cris.com).)

    The point here is that vacuuming toner, which is carbon black and latex, will create a static charge. Using a vacuum that is not intended for this purpose can cause the following. You can blow sensitive components on circuit boards, expecially bias boards on the developer units of the larger copiers and the transfer belt power packs of the smaller machines. Another worrisome possibility is an explosion. I have seen two old toner capable vacuums ignite the toner dust as it went through the vacuum. I admit this is a very rare phenomenon but I would think it would be even more likely in a vacuum not designed for sucking up toner. I would suggest reading on the side of your toner bottle. Most bottles caution about disposing of toner by incineration, the stuff is explosive if the air/fuel mixture is right. It probably wouldn't do much harm but I bet it would play hell with your office.

    (From: Le Baron O. Ferguson" (ferguson@math.ucr.edu).)

    Thanks for the response. I think I should state for everyone reading that I am now convinced that there IS a serious fire hazard. One person who responded (by email) has seen two of them "light up."

    Comments on copy problems

    (From: Copenhagen Cowboy (cowboy@fastlane.net).)

    Copy problems can be hard to figure out, but given the evidence the copier gives you, you can now probably determine what to check.

    Black or dark lines are mostly caused by dirty optics (not enought light getting to the Drum) Blank copies might be a broken corona wire, or even failed High Voltage board. Black copies can mean a bad exposure lamp (broken or burnt out) or failed exposure lamp thermal fuse. Black copies with even blacker images in them could be overtoned (too much toner in the developer unit) or bad drum ground (the drum cannot discharge {the voltages have nowhere to go, so they just stay on the drum). Bad drum grounds usually pull developer, and you get the grit on the copies.

    General image quality problems - Clean the optics first!!

    The office here has a Xerox 5310 (Rebadged-Sharp) and it's been getting progressively worse with respect to overall image quality. A new drum ($140) has helped but things go down the crapper too fast for comfort. (~90 thousand copies, 4th drum now.)

    So, I cleaned the optics. That was it! 2 mirrors were CLOUDED with white dust. Geeeee, do ya think that could do it? ;-)

    Light-path in each is going to differ but I'll give you this one as an example. The 5310 can enlarge and reduce and the table does NOT move, i.e., more hoopla under the glass :-)

    
     ddddddddddddddddddddddddddddddd                         LEV 1
     ========================================= glass         LEV 2
        [1    ]                      \2                      LEV 3
       A[  \  :                        \                     ..
        [     ]                          \B                  ..
                                         /                   ..
           4/          ()L             /3                    ..
        C /            ()            /                       ..
    -----|  |---------------------------------------         LEV 4
         5\                          \6                      LEV 5
            \                          \D                    ..
                          [P]   .--.                         ..
                              /      \                       ..
                             |  DRUM  |                      ..
    

    Legend:

    dddd - represents the paper document you are copying
    A - Moving assembly that holds the exposure lamp and (1) first mirror.

    B - Moving assembly containing 2 mirrors: (2) second mirror and (3) third mirror.

    L - Movable assembly containing enlarge/reduce lens.

    C - Movable assembly (covered by black sheet-metal cover that also covers the top of the Lens) containing (4) fourth and (5) fifth mirrors.

    D - Fixed (6) sixth mirror that directs light onto the drum.
    P - Erase lamp assembly.

    Layers:

    LEV 1 - External to the copier, look for whiteout and layers of smudges.

    LEV 2 - Glass pane (see LEV 1)

    LEV 3 - Scanning layer, exhaust fan to keep dust from settling... Does that for about 2 minutes and then starts accumulation of very fine dust on all mirrors. :-)

    - Some assemblies are covered to 1) keep the stray light and 2) reduce dust accumulation - do NOT skip them in cleaning. *Especially* Assy C!

    LEV 4 - Structural sheet-metal separates Scanner from drum/toner assembly below.

    LEV 5 - Toner and Paper transport layer

    See the document: Notes on the Troubleshooting and Repair of CD Players and CDROM Drives for appropriate chemicals and materials for cleaning mirrors (and lenses) In a pinch, a bit of my [clean] 100% cotton T-shirt works well - followed by a good blow with duster can and soft, [fake] camel-hair brush. The object is to have a mirror as clean as the minute it was made.

    Apply a half dozen drops of non-detergent light oil onto the felt 'washers' on any movable assemblies' rods, if present. Might want to dampen a piece of cloth with oil and wipe the rods. This helps to prevent drips, etc.

    I would remove the glass (LEV 2) completely from the machine and give it a good scrub from BOTH sides with the usual chemicals (ammonia-content is superior, IMO) for 2 reasons: 1) to keep ALL overspray from rest of machine and 2) to do a really GOOD job... not half-assed worried about overspray :-)

    Don't skimp on corona wires... many machines include a plastic/felt wiper than prevents injury to the wires, USE IT. I keep a supply of scavenged wires for times when it goes 'TwhanNNnnnG' for the last time... :-|

    Density control - some machines, the 5310 included, have a density adjustment under the front cover. This is in addition to the DARK-NORM-LIGHT control on the front panel. I find that after this cleaning, it can be turned back to somewhere near the middle. This cleaning is often needed if even *that* adjustment doesn't compensate for crappy copy :-)

    After this cleaning, the copy will *overall* have whiter (read: less toner wasted) background... this will improve contrast and lead to greater toner cart life. We get them recharged, BTW, for ~$49 or so... New it's $120 from Office Depot. ARGHHHHHHHHHHHHHHHHH....

    Diagnosing 'blank copy' problems

    "I have just cleaned a Sharp SF 755 which was quite dirty but now will not copy at all! No error codes paper hot on exit, all seems well but the paper is blank."

    (From: Bruce L. Miles (henry31@prodigy.net).)

    Two things to try:

    1. Peek inside and see if you can detect a latent image on the drum. If an image of your test document exists on the drum, then the main corona unit is working at least.

    2. Perform a 'Skyshot Test'. Leave the cover off the glass and take a picture of, well, the sky. It is a good idea to cover the leading edge (left side) of the copy glass with a piece of paper so that the fuser doesn't try so hard to jam on a solid sheet of heavily tonered (blackened) paper.

    If the skyshot print comes out white (it should be entirely black since the amount of light hitting the drum compared to reflection from actual copy is nil), and you DID have a latent image on the drum, the prime suspect would be the transfer corona - it is not receiving the high negative voltage needed to pull the positively charged toner off the drum and onto the paper. The culprit could be the corona wire being broken, the corona assembly not making a good connection into its high voltage socket, or even some weirdness going on with the high voltage power supply - i.e., supplying proper voltage to the main corona, but nothing to the transfer corona.

    Copies too dark 1

    "I have an old Savin model 7010 copier that works just fine except it prints to dark. I have to keep the "lighter darker' control to max "lighter". I have replaced the (expensive) OPC cartridge and cleand all the wires and mirrors etc. It works best right before it runs out of toner, of which it uses up to fast. Any info will be appreciated!"

    (From: Thierry Thdereck (thdereck@aol.com).)

    There also other reason a copier is darker than it should:

    So you may have lot of work if you don't know the right setups before having good copies.

    Copies too dark 2

    "Canon NP-2015s ... prints very dark, with "water stained" appearance. All controls full light gives a 'readable' copy with a dark grey background. I have been told everything from 'wrong toner' to moisture in the toner. The guy who brought it to me doesn't know. Before I vacuum out the toner & stick a $25 cartridge in it, could this be a bias problem?"

    (From: Bernard Morey (bmorey@aardvark.apana.org.au).)

    Have you tried cleaning the corona wires? There are generally two modules. Pull out and clean with cotton-swabs (Q-tips).

    (From: Lionel Wagner (ck508@FreeNet.Carleton.CA).)

    If your dark grey background is not uniform, you will have to vacuum out ALL the old toner, and thoroughly clean the roller that transfers it to the drum. Do not use abrasives, as the surface of the roller is very critical. If this restores even grey background, you can think of adjusting the bias voltage.

    Copies too light

    Aside from a misadjusted 'darkness' control, improper voltages, dirty corona wires, and worn drum, don't overlook the trivial: your paper may be incorrect or damp.

    (From: Morton Lee Cohen ya484@@vtn1.victoria.tc.ca).)

    I am a former copier tech. that worked on Konica copiers. To get good results from your copier, a periodical maintenance should be perform on the copier, every so many copies or once a year, depending on which event occurs first.

    During a PM, the optics, corona wires, drum gets cleaned. The Fixing unit gets cleaned, and serviced. The Developer gets replaced. And adjustments are performed, if needed only.

    The developer transports the toner to the charged area of the drum and developer gets weak over time. Developer is made up of iron filings.

    Previous copy doesn't erase from drum

    "I recently purchased a Mita DC-111 copy machine, and I finally it to make copies, now I have on big problem. When I do more than one copy, the drum doesn't fully erase itself, thus leaving ghosted images on the remaining copies that are made. I don't know much about copiers, and I really just lucked into getting it to actually make copies. Any help would be appreciated.

    (From: Jeff Roberts (jroberts@axionet.com).)

    Make sure it is the drum that is not cleaning by measuring the distance between the origional image and the ghost image on the page. that distance will be the circumference of the drum if that is the cause. The drum assembly should come out as a unit. Take it out and make shure to quickly remove the drum from the unit and put it in a dark place so that it doesn't become light shocked. then look for a blade of some sort, it may be neoprene or rubber. it is usually on a actuater assembly that can push it out to make contact with the drum and then retract it back (possibly a solenoid/cam) this blade does the cleaning by scraping the excess off the drum. If it is hard or brittle it will have to be replaced but cleaning it with a 70% solution of rubbing alcohol may be enough. After cleaning it rub some toner along the edge to re-lubricate it and reassemble and try that. Also check that the drum unit is not clogged up, the waste toner goes somewhere and if it uses a sump and the sump is full then it will ghost no matter how clean the blade is.

    (From: Vance Harlow (musk@aol.com).)

    On copy machines and laser printers with long life drums (ones where toner can be refilled without replacing the whole drum assembly) the wiper blade will usually fail long before the drum does on machines that are not used frequently or used to print one or two copies at at time. If the service department is not aware of the problem, or the manufacturer doesn't supply the blade as a separate part, you'll usually end up getting stuck for a whole new drum assembly when all that's needed is a wiper blade (this is the rubber or plastic blade that bears on the image drum, not the felt wand, BTW).

    Usually the clue will be that the first few copies are bad, but then quality improves. If that's what's happening, usually replacing just the wiper blade will cure it.

    Since the blade costs only $10 or so, it can be worth giving it a try before replacing the drum assembly. This has worked on both my Canon 1010 copier and various OKI and GCC laser printers.

    Finding the blade can take some doing - when I called the local Canon distributor, they couldn't give find a part number, even though I'd bought a couple years earlier and knew it existed as a replacement part. Luckily, one the the service techs was able to dig up the number. OK doesn't list them at all - they only sell the the whole assembly. But you can get the blades for most laser printers, and some copiers, from American Ribbon and Toner or Computer Friends. Since the drum assembly on the old Okis like the 400 and 800 series, and the GCC/Mac versions lists for $250 or so, one frequently runs into them with bad drums for $0-25. I've revived a half dozen of them simply by replacing the blade - knowing this trick is like having a free source of laser printers! the OKI blade pops right in with only minor disassembly; the Canon is a bit more trouble.

    Computer Friends also has a teflon wax for reconditioning drums - they claim it will protect the coating, fill in small scratches and treble the life of a throw away drum, and vastly prolong the life of long life drums. I've tried it so far only on an old 1010 drum, with mixed results so far (worked great at first, but now copies are getting dirty - don't know if it's the wax acting up, the drum going despite the wax, or other problems. They also sell the Oki drums for about $40, and drums for many other printers but not copiers.

    Copy quality degrades with use

    (From: Lionel Wagner (ck508@FreeNet.Carleton.CA).)

    If you are lucky, cleaning the optical path: mirror and lens will help. Cleaning the corona wires is a routine necessity. Use two Q-tips, one on top, the other on the bottom, of the fine wires and travel the length. Soak the Q-tips in lighter fluid, my favorite all-purpose cleaner.

    Probably the photo-sensitive drum has aged. A sure sign of this is a difference in density between the first and last copy of a long (50 copy) print run. This is particularly noticeable after the copier has not been used for some time.

    (From: BRADS TV (bradstv@aol.com).)

    I have found that dirty mirrors and optics will cause smudging, dark copies and generally poor quality copies. Try cleaning these mirrors in the optical path. NOTE these mirrors are first surface or front silvered mirrors and they scratch easily. Also look carefully for the complete light path from the exposure lamp all the way to the drum, you will find several mirrors mounted at angles to direct the image to the drum . You are right in the fact that the drum can cause poor copies but cleaning first might be the first step. Brad

    Copier error codes

    Most modern copiers produce an error code of some sort when, you guessed it, they detect an error. However, there is no standardization. So, other than posting to sci.electronics.repair or checking this FAQ, how does one determine their meaning?

    (From: Sid Ashen-Brenner (sashen@midusa.net).)

    Affordable Photocopiers (http://www.photocopiers.com) may have a Service sheet for about $15.00 that would contain the codes for your copier. I got the one for my Mita DC 1255 from them. They also sell parts and supplies at a fairly reasonable rate.

    Canon PC25 copier problems

    "The lamps goes on my Canon PC-25 but I get nothing but black copiers. I'm told the problem could be a broken corona wire. Where is the corona wire located? What does it look like? How do I determine if it's broken and how is it replaced? Thanks in advance."

    (From: Lionel Wagner (ck508@FreeNet.Carleton.CA).)

    I doubt the cause is a broken corona wire. If this were the case you would get white copies, instead of black. Check the bias lamps are coming on. They are a string of small lamps located 'downstream' from the transfer corona (located at the bottom of the drum).

    "I have an elderly Canon PC25 Copier, which still runs well apart from two problems.

    The first is an intermittent fault which makes it turn out blank paper, usually on switching on but occasionally during a run. I assume this is a faulty joint on a circuit board because opening the machine and slamming the top down usually cures it for the moment.

    The second is that the light/dark slider has to be at one end of its range to get satisfactory copies.

    Are these common faults on this model with a recognized cure? Although it is expensive to run, I seldom need enough copies to justify purchasing a new one."

    (From: Lionel Wagner (ck508@FreeNet.Carleton.CA).)

    You're right about the bad connection fixed by the vibration of closing the cover. Your exposure control is probably at darker than normal to compensate for aging of the photo-sensitive drum. Some compensation is possible by adjusting the high voltage or (I prefer) the toner wheel bias voltage. I'm assuming your corona wires are clean, of course.

    The mysteries of developer

    "My owner's manual never mentions developer anywhere. This copier uses toner cartridges which mount above the dispenser and drop toner into a mechanism which distributes it to the drum. There is a white plastic bottle which catches excess toner and eventually fills up and needs replacing. They say to replace the bottle, but I just empty it, wipe it off and reinstall it. Only the toner cartridge and the bottle are mentioned in the useless owner's manual."

    (Responses farom: Nate Morrison (nmorriso@plains.nodak.edu).)

    Well, that's all they think you need to know. They want you to call the dealer if the copies are crappy.

    The reason you should just toss the used toner bottle is the dust--it is messy and not good for your respiratory tract.

    Some copiers use developer; others don't. How long it lasts before it runs out is basically in how the copier is engineered. Some gets carried away every time you make a copy. Pretty soon there isn't enough to carry toner to the drum anymore.

    "So, if my copier needs developer, how do I obtain it? Where does it go? I suspect that I purchase a bottle of these 'iron particles' and dump it into the slot where the toner drops into, but I don't want to do *anything* until I know the right thing to do."

    If you need developer, you can get a kit from the local service shop. You'll pay plenty, to be sure, but not as much as if someone came out and did it for you. It might not be a bad idea to invest in a service manual - I got one for our Minolta for around $20.

    "Why is this rather simple maintenance procedure kept a secret from the owner? Is Mita trying to make money for their authorized repair outlets?"

    Well, that's another of those reasons they want you to hire the serviceperson at a ludicrous rate. (the local place gets $99/hour!) You have it pegged.

    Another reason is that they want to promote the idea that _their_ copier is service-free. Telling any prospective buyer that in 50,000 copies it will require professional service is NOT a selling point. :-) The copier is designed so you can change toner and paper and that's it. Anything else is always "see your authorized dealer" in the useless owner's manual.

    Problems with Ricoh copier

    "Some time ago I got a big and heavy RICOH xerox copier and I have got a problem with it:

    The output of the device is very poor: Passages which should be black are only light grey. If the contrast is turned on to the maximum the whole sheet gets grey. The copies look as if there would be only a little bit of toner on the drum. In order to solve the problem I already checked the optics, the corona wires and voltages and I filled up the toner. My question now is whether it is possible that the drum is defect? What else could cause such a failure?

    Since the device is quite old (1988) spare parts are not easy to get, but the mechanics looks quite well so I do not want to loose the device."

    (From: Copenhagen Cowboy (cowboy@fastlane.net).)

    I am a Copier Repair Tech and have a few suggestions for you. First, what does a Blackout look like? What I mean is, make a copy with the lid up, and check to see how Black it is. Note to see if there is any "Grit" on the paper. Most likely if there is no Grit, and the Black area is Grey, then I would suggest changing the Developer (or you might even have a Developer Drive Problem [gears and stuff]). If there is a fine layer of Developer on the page, you probably have a Drum Grounding problem.

    Toner sensors?

    I took one of those apart and found something that looked like a piezo element with 3 wire connections to concentric rings. I looks to me like some sort of resonator but I have not attempted to analyze the circuit.

    My wild guess would be that the frequency changes with low toner or something like that.

    (From: Morton Lee Cohen (cx163@FreeNet.Carleton.CA).)

    Probably the disks stir the toner for even dispersion, and break a photogate to tell the controller PCB that there is toner there. Some Cannon laser printers/photocopiers use magnetic sensing of the toner level. Most Okidatas use the photogate sensors with magnetic toner agitators.

    (From: Anonymous.)

    On some Canon machines they do indeed use a piezo electric speaker for sensing the toner level. The speaker emits a particular frequency that bounces off the far end of the hopper/cartridge and causes a change in resonance when toner is present.

    Comments on copier cleanliness

    Copiers are about the ickiest equipment to dismantle with all that black toner over everything!

    (From: Morton Lee Cohen (cx163@FreeNet.Carleton.CA).)

    There is toner over a lot of places in copiers, not so much due to customer problems, but due to lazy service technicians, trying to raise their average call per day ratios. Service Technicians often get calls to do Periodical maintenance on copiers late in the day and rush to leave an account at 5pm, so many overlook non-important parts of the copier to clean during a maintenance of a copier.

    And as far as the toner sensor goes, lots of times toner cakes on the sensor and the copier never tells the customer that it needs toner, when the copies start getting light, that the copier starts pulling developer from the developer tray, and that it gets messy.

    Not all copiers are created equal and not all service technicians are created equal, either also. Some will always be better than others. But the best policy is always to tell the truth. My telling the truth, you tell the customer where the problem exists.

    Never lie, because if you lie, one always has the remember what they lied about. From the writers of Star Trek - The Next Generation. And I practice that in dealing with customers and myself.

    Gray tinge on Xerox 5260 Copier

    "Earlier this year, I inherited a Xerox 5260 personal copier. It works well except all the copies have a grey tinge to them, even when the auto-exposure control is set to light. The grey background is visible over all the page, and gets noticably darker when the auto-exposure control is set to dark. Is it time to replace the copy cartridge?"

    (From: Lionel Wagner (ck508@FreeNet.Carleton.CA).)

    Your toner/developer wheel bias voltage may be wrong. When light strikes the photosensitive drum it does not completely discharge it. The toner/developer bias voltage must precisely match the residual charge or grey background will result.

    Streaky copies

    (From: Bernard Morey (bmorey@melbourne.DIALix.oz.au).)

    Well, I discovered that streaky copies are caused by dirty corona wires (fixed easily, although 1 unit was held by a screw-in plate, rather than the usual pull-out method) and that dirty corona wires seems to be caused by excessive toner deposition (haven't figured that out yet).

    (From: Lionel Wagner (ck508@FreeNet.Carleton.CA).)

    If the streaks are white, in black areas, clean or replace the corona wires. If the streaks are narrow black and run the entire length of the page, replace the soft plastic wiper blade on the drum (and hope the drum is not scratched). Black smudges are related to the toner/developer purity. Replace both.

    Toshiba parts

    "Can anyone tell me where to get old / deleted spares for Toshiba photocopier model No BD-3110, or where to get the following for the mentioned copier. TEC High Voltage Unit (HVT-T)..Model No AFT-375-A

    (From: Filip M. Gieszczykiewicz (filipg@repairfaq.org).)

    Greetings. Give URL: http://www.europa.com/~tait/copiers.htm a go. They have all the usual stuff (rollers, picker fingers, lamps, masters, etc) for many Copiers. My $200 order is in the mail. :-)

    [dig dig]

    Drat, they don't list prices for anything but toner for that one. Their number is 1-503-293-8071 but you might want to try something closer to home (than Portland, Oregon - 1/2 world away :-) because the shipping *will* kill you...

    Canon PC20 cold fuser

    "I'm trying to repair a Canon PC20 copier, on which the main problem is a cold fuser.

    The fuser lamp has blown, but it looks as though it might have overheated before doing so : in two places the tube has expanded as though it got very hot while under compression from the spring endcaps. The 47R sacrificial resistor in the fuser lamp relay circuit (I think it's there to stop the control circuit holding the lamp on permanently) has also gone open circuit.

    What would cause the lamp to overheat ? The thermistor (which was coated in toner) appears to work : it measures about 300K at room temperature and falls a few 10K with finger heat, so it's not open circuit (though it might be incorrect). I'd like to check out the rest of the copier before buying spare lamps etc. - can anyone tell me what the thermistor should measure (hot & cold) so I can test the control circuit and fool the copier into working?"

    The thermistor may be working. It sounds like a bad triac or whatever is used to actually switch power. Get a 300K pot as a sub for the thermistor during testing.

    (From: Adrian Godwin (agodwin@piresearch.co.uk).)

    I had a go with this : about 4K fools the control board that the roller is hot, and allows the rest of the cycle to run. However, this _doesn't_ cause the heater power to switch off - in fact, only turning the resistance almost to zero has any effect, and at this point it appears that the controller attempts to burn out the 47R resistor.

    This might make sense, except that as far as I can see there's no way that the control board COULD turn off the heater power without burning this resistor : the fuser lamp is powered through a relay which is excited by the main 24 V supply via this 47R resistor. There's no way that I've seen so far that the controller can turn off the lamp other than to short out the relay (which burns the protective resistor). So I wonder if there's no control - just a monitor for the copier control board and an overtemperature safety circuit that disables the fuser lamp (and simultaneously disables themain motor control triac). This surprises me, as I have a Canon SX-based printer where the lamp power cycles (though not using a relay, as it's quiet).

    (From the editor).

    There must be a triac or other mechanism for cycling power to the lamp - its temperature must be tightly controlled regardless of line voltage fluctuations and ambient temperature. (--- sam)

    Broken Sharp Copier

    "My Sharp copier is dead again, it's an old one. It is flashing "U1" which I think means internal lithium battery is dead, but it won't reset. Somebody emailed me the secret code once, but I have since

    (From: FAXFIXR (justdfax@cdepot.net).)

    The prefix is always CROP (clear, repeat, zero, pause) and the code for a U1 reset is 13 then press the copy button. So it would be C R O P 14

    Resetting Sharp Z-25 copy count

    This may be necessary if you run the copier past the recommended life of the drum but still get acceptable performance. You then need to trick the copier into thinking a new drum has been installed. Other copiers may require similar treatment as well.

    (From: YonyMar (yonymar@aol.com).)

    You need to reset the counter inside the copier. When you buy a new drum, it resets the counter, however it can only do this once. Unplug the copier and remove the drum and toner cartridge, at the back of the machine where the drum would slide in look for a small metal lever, push it in with your finger to reset the counter. The counter numbers are covered by a black plastic cover.

    Sharp SF-71 copier will not reset

    "I have an old Sharp SF-781 copier which will not reset. The diagnostic code "H1" is flashing on the display and the copier will not reset to the operation condition, using the keyboard clear sequence.

    I have been able to reset the "H1" code before, but this time no luck."

    (From: copymann@usa.net).

    H-1 means an open thermal fuse on the upper fuser roller. Remove the cover on the fuser rollers and you will see a ceramic fuse located on the top plate. Check the fuse for continuity. If bad replace it with one with the same temperature rating, ( or close to the same ) Sometimes you can find them a radio shack. If not email me and I will send you one. If you order the fuse from sharp it is pretty expensive. If the fuse is good check the lamp in the upper fuser roller or the upper lamp triac. 99% of the time it is the fuse.

    Sharp SF-7100 copier drum replacement

    "I have a Sharp SF-7100 copier. When I call about a replacement drum, people tell me it uses a Master. What is a Master? Can I install it myself. Does anyone have a service manual for this copier?"

    (From: Lionel Wagner (ck508@FreeNet.Carleton.CA).)

    The Master is the SURFACE of your photo-sensitive drum. In a brilliant design concept, Sharp allows you to easily replace a thin (in your case) cardboard sheet, that effectively gives you the performance of a new drum at a fraction of the cost. There is no wiper blade, residual toner is removed by polarity reversal and is re-absorbed in the developer. Cardboard Masters for your machine are in short supply. Let me know if you can find some. You may wish to upgrade to an aluminum backed Master used in model SF760, but they are much more expensive.



  • Back to Printer/Copier/Fax Repair FAQ Table of Contents.

    General Problems

    Panasonic 1124 power supply problem

    The following, of course, also applies to many other printers and other electronic equipment, for that matter.

    "I have a Panasonic 1124 printer which keeps blowing the only 250V 3A fuse on board. The fuse burns as soon as the power is turned on.

    I unhooked the components which connect to the logic board - i.e., printhead and tractor feed.

    Is it possible that the problem is in the power supply? If it is, what can it be? (The bridge rectifier consists of four hefty diodes)."

    (From: Bruce A Haugh (yrp456@freenet.mb.ca).)

    With the power supply disconnected from the rest of the printer circuits, blows the fuse, the problem is with the power supply. I have a Raven PR-9101 (made by Panasonic) that has the exact same symptoms. Turns out that one of the secondaries on the power transformer has shorted. You'd need schematics to confirm voltages.

    (From: Robert McCallum (simply@sk.sympatico.ca).)

    I've fixed quite a few panasonic printers and yes 90% of the time when the machine is dead, it's one or more of the bridge diodes.

    (From: Kerry Messana (messana@capital.net).)

    It's fairly simple to diagnose where the problem is originating. If you unplug (if possible) the output cable from the power supply and it still blows the fuse then the power supply is at fault. As for what could be wrong, well, I am not familiar with the particular supply. If it is a linear supply a good place to start is the bridge circuit. If it is a switching supply you could also start there but there are more possibilities further on.

    (From: John A. McCulloch (advp@notnow.com).)

    Another very common problem with the whole Panasonic 11XX series of printers is the zener diode and pass transistor. When the diode shorts, the transistor blows, and I mean *blows*!

    Cannon LBP-8 A1 Printer 40 and 22 errors

    (From: GTRIST (gtrist@aol.com).)

    The 40 and 22 errors normally refer to a problem with the cabling etc. Make sure that you have it cabled properly. Also, it can be a bit tricky changing from parallel to serial I/O. Make sure that it is indeed selected.



  • Back to Printer/Copier/Fax Repair FAQ Table of Contents.

    Fax Machines and Scanners

    Fax/scanner striping

    "One of my fax machines produces some black stripes in copy mode and on the documents received on another machine. Are these stripes caused by a malfunction of the optical diodes bar, some other electronic failure or by dirt?"

    (From: Paul Grohe (grohe@galaxy.nsc.com).)

    Probably by dirt or a paper shreds stuck in the optical path.

    A common cause is Liquid Paper. Somebody makes a correction and sticks the not-yet-dry correction into the fax. Then the still-wet correction fluid makes a streak on the pickup window as it passes by. Subsequent faxes will now have streaks.

    I had the same problem. It turned out that the ink from a faulty page stamp had dripped down onto the mirror.

    Generally, the paper is moved and the optical path does not move. So if there is something blocking the optical path, it will show up as one continuous image, or stripe. The "blockage" can be a paper shred, ink, dust or even a loose wire.

    The image is usually bounced off a long, wide mirror and then into the CCD pickup somewhere in the bottom of the machine. If anything is in this path, it will cause that problem.

    Open er' up and just look around inside for dirt and loose debris. Then inspect the *ENTIRE* optical path. BUT DON"T REMOVE ANYTHING!!! You don't want to mess up any alignments.

    If the fax is old, or is in heavy use, you'll probably find that it is in need of a good cleaning. Clean the mirror and blow out any dust or junk.

    Also check the automatic paper cutter (if it has one) for paper shreds.

    Brother Fax machine feed problems and cleaning

    (From: (Al Savage) asavage@iname.com ).)

    I suggest you look carefully at the paper feed mechanism. Brother has a reputation with me for feeding the scanned documents poorly, resulting is overscanning the same area two or more times, which results in "stretched" text or graphics. If this seems to match your symptom, cleaning the feed rollers will probably cure this.

    The downside is that a couple of the Brother fax machines that I've had to clean force you to do an unbelievable amount of teardown work to get to some of the feed rolls. Fortunately, I don't work on them anymore .

    Brother IntelliFax 950M transmits black messy lines

    "I have a Brother IntelliFax 950M plain paper fax that transmits with black lines or dots. When making just a copy the prints are just as bad. The prints are tiny square dots that make up these lines. It looks like digital problems and not dust on the lens. I'm not very familiar with plain paper faxes. It looks like a scanning failure. I'm guessing at a scanner or some other circuit board. Receiving faxes are ok. Has any one had experience with the Brother Intellifax 950M? Also, Brother has a part called a NUC printed circuit board. Would this be some sort of scanner?

    (From: MECHSHOT (mechshot@aol.com).)

    This problem is a known fault because Brother assembled these units with what turned out to be defective scanners. They would fail after some time, typically withing 2 to 3 years. I know, we have 3 that failed and they were all built around the same time. The good news is Brother will supply the part (worth about $120) if you pay for the labor (usually around 55-85). Contact Brother Customer Service (the 800 number is in your owner's manual) and they will refer you to an authorized service center. Get a bunch (if possible) of different shops in your area, they charge different labor costs. You must supply your machine's serial number to see if it is eligible for this program.

    Then customer service will make out work order, send it along with part to center of your choice.

    All of the centers I spoke to were aware of this problem and were confident once fixed, the units were very good and reliable afterwards. Check local office equipment repair houses for more info too. Hope this helps.

    Hewlet Packard LaserJet FAX (HP C1740A)

    "This machine is copying and sending fax with a line about 3 cm across straight down the paper. This is a thick black colour. Any ideas as to the cause? I have already checked that there is no paper jam or any block to the sensor.

    (From: Robert Macy (robert.macy@engineers.com).)

    I'm not familiar with the HP LaserJet FAX, but I assume the LJ scans in a page and then sends it, or copies it. Since the black stripe is unique to sending or copying a document (does not appear on incoming faxes), the problem is in the HP's acquisition system.

    It can either be the illumination of the page over that small section (no light, looks black) or it can be a whole section of the linear CCD went out (the whole section is losing any charges built up, looks black) or it can be the memory where the image is shifted into (dead RAM section, looks black).

    I don't know how the HP illuminates its pages. Is it a flourescent tube across the page, or a row of LED's? Knowing HP's penchant for reliability I would almost assume the engineers went after LEDs. And the section that lights up that 3cm width could have died. However, if it's illumination that died, usually the edges are "soft".

    If it uses flourescent light (remember I said I'm not familiar with this scanner), then it sounds like the CCD, or memory, has gone funky on you.

    If the memory where the image is stored has a section that died, then you could end up with such a stripe also. Even my ScanMan Plus by Logitech has occasionally put a black strip on the first 10% of the pixels. To solve that I have to do a full power OFF reset (not reboot, but full power OFF)

    You can look for the illumination uniformity with your eyes. Just make sure there is no section that's darker by a noticeable amount (not necessarily black, but just a lot dimmer)

    Put a sheet of white paper in the machine and put a scope on the output of the CCD & sync from the line reset. Make sure that the CCD is supplying active light information across its whole field of view. If not, you can go from there.

    If the data coming out of the CCD looks good, then it's probably the memory holding that line. You can probably change the line storage RAM and fix it.

    These are just guesses based upon how I perceive the HP LaserJet to work. Hope somebody that *knows* this unit jumps in with more specific help.

    Paper sense problems with Brother Fax

    "I have a Brother 470 FAX machine that appears to have a broken micro-type switch that detects there is paper WITHIN the front feeder.

    Also sometime it jams paper at the rear. It looks like it cuts the paper off (the copy or document report) a little short and the roll of FAX paper pulls it back towards the roll. Thus when the roller advances the paper next time it gets jammed as it isn't in the feed slot?"

    (From: "NO UTN" (utn@pi.net).)

    My experience with brother fax:

    There are 2 detectors at the output of my Brother Fax, do not know type but it uses a roll of thermal paper.

    Detector 1 simply uses an IR LED and IR receiver to sense the paper.

    Detector 2 is on the cutter, when cutting paper the motor turns by means of a worm-wheel a wheel that moves a handle that lets the cutter move. On the wheel is a detection switch, there is a ring on the wheel from which one part is taken away to be able to detect the home position. If cutting starts the wheel has to be turned in a maximum time, if not the wheel is turned back and cutting stops. The Fax gave and error message. Solution: put some oil at the motor and it works again.



  • Back to Printer/Copier/Fax Repair FAQ Table of Contents.

    Miscellaneous Problems and Procedures

    Cleaning the fuser roller

    Of course, the stuff mentioned below is probably banned now.

    (From: uiop@cyberramp.net).

    When I worked servicing copiers for Canon, we took the roller out, the wiped it down with tri-chlor-ethane, which did a great job.

    (From: Joseph Patrick (jpatrick@edge.net).)

    The best way to clean a fuser is to use a very light coat of silicon oil. This is used on the heated fuser as well as the pressure roller.

    The function of the fuser is to bind the ink to the paper through heat and pressure it should not accumulate any ink during normal use, it doesn't remove or collect toner normally, unless the surface is dirty or deteriorated. The teflon on the main fuser should be slightly shiny much like the surface on a Silverstone(tm) frying pan.

    The item you were thinking of is the drum wiper blade which is a part of the drum assembly and is usually responsible for streaks / smudges that persist on the photo drum's surface and make permanent smudges on copies.

    I learned of the silicon oil treatment from a 3M service rep. I was using alcohol in the copiers I serviced up to that time. He showed me the way to do it by wiping the fuser components with a non linty rag with a little oil on it until the rollers were completely clean then drying them with another cloth. The job naturally was done with the rollers fully dis-assembled but in his case could be done with minimum removal just so the rollers could be turned and reached without touching the drum assembly, the oil would kill it.

    Streaks on laser printer output

    (From: Bruce Tomlin (btomlin@crl.com).)

    There is also a drum cleaner blade which cleans excess toner off of the drum between pages. On a regular copier, this would show as streaks or even a double image that only shows when you print more than one page at a time.

    HP plotter communications problems

    "I'm repairing HP plotter 7550 and there are some chips that I suspect to be broken. They are related to serial communications ( thats what is broken). The chips are labeled as 1820-3321 and 1820-3322. I suspected that they could be 1488 and 1489 but changing them did not fix the problem"

    (From Paul Grohe (grohe@galaxy.nsc.com).)

    Been there, dunnit...

    The serial interface on the 7550's is...well...weird!

    Without the proper cable, the interface will seem "dead" or unresponsive.

    First, you need to use the *male* 25 pin connector, not the female one (which you may automatically assume).

    It requires a specially wired serial cable (you can build it yourself). A standard modem cable with a F-F adapter will not work. There are a few handshake lines that need to be wired. Note that you will also need to get a *female* plug for the plotter end of your serial cable.

    There are also some menu setups required.

    HP has a diagram of the needed cable and menu setups on their FTP site. Get these two documents:

    Everything you need, short of RTFM, is in these files.

    (These no longer exist. If anyone knows what happened to them or has the info, please send me mail via the Sci.Electronics.Repair FAQ Email Links Page. --- Sam.)

    There are some other plotter docs at:

    The 7550 suffers from paper pickup rollers that dry/wear out and have trouble picking up the paper from the tray. If you look at the rollers, there is a flat portion. The edge of the "flat" part wears down and becomes rounded, causing it to no longer pick up paper. Try to keep the paper tray as full as possible. Overfilling the paper tray will cause it to pick up multiple sheets, and that can cause a real mess!!

    Check the paper feed slot and pinch rollers for shredded paper.

    Also, check and make sure the screw that holds the pen carousel together is tight. If this screw becomes loose, it will cause pen loading problems.

    It's a "helluva" plotter when it works!

    Okidata FAX machine - Printer Alarm 4

    "I am currently working on a Okidata fax machine Model Okifax 2100. The display reads: PRINTER ALARM 4[TEL], CONFIRM AND 'STOP'

    If anyone has seen this problem and would be kind enough to share the fix it would be greatly appreciated."

    (From: Darrin Acreman (darrina@profax.com.au).)

    In all Oki plain paper machines, 'Printer Alarm 4' is caused by the fuser section failing to reach the correct operating temperature. The most common cause is a blown thermal fuse in the fuser section.



  • Back to Printer/Copier/Fax Repair FAQ Table of Contents.

    Unresolved Problems

    Packard Bell laser printer - strange bug

    (From: Jordin Kare (jtk@s1.gov).)

    "Just picked up a used Packard Bell laser printer with some problems and could use help...

    Print engine is not one I'm familiar with. It's an 8 ppm engine that uses separate drum and developer assemblies. The drum assembly is attached to the top section, which hinges upwards. The developer assembly is attached to the bottom section, and uses a replaceable cylindrical toner cartridge similar to that used in older Canon NP-series copiers. The whole developer assembly can also be removed.

    Paper tray mounts underneath unit, and paper follows an "S" shaped path through printer, stacking face-down on top. Front panel has a ~16 char. LCD display and typical button/LED set (ON LINE, Form feed, Menu, Test, Reset).

    (Sorry, don't have the model # to hand. Printer was built in late 1993.)

    Printer executes power on self test OK, warms up, and goes on line.

    Problem 1: Take it off line and push test, and the motor whirs briefly, then stops. The LCD display then reads: 'ERROR 74-M: MOTOR'. Reset has no effect; printer must be power cycled to get it to restart.

    Interesting variation: The top section is held down by two large catches at the right and left sides of the printer. The 'hooks' are released by a button on the top section. It's possible to get only the right-side hook to catch, leaving the left side 'loose' and raised by about 1/4 inch. In this condition, the printer will start up and work fine (except for problem 2 below) for many pages. Eventually, it will stop with ERROR 74-M again. Pushing down the left side will cause an immediate ERROR 74-M.

    I assume there's something binding or sticking a bit in the various rollers, such that the motor draws too much current or otherwise triggers an error when the top is latched down. Releasing the top on one edge reduces the pressure on the various rollers and thus the load on the motor. But I can't find any obvious points of sticking.

    Problem 2: When the printer *does* work, with the cover popped, the leading edge of the page, down to the first line of print, is dark grey. The grey is faint on the first page or after a restart or long idle, but uniformly dark on all pages thereafter. It tends to be striped along the page (varying darkness as you move left-to-right; uniform as you move top-to-bottom). The grey disappears at the first line of text. There's also a slight "ghost"; text printed near the top of a page is repeated faintly further down the page, apparently displaced by one rotation of the drum.

    This seems most likely due to a bad cleaning blade or clearing corona. Anyone have any suggestions other than replacing the drum assembly? Also, anyone recognize this print engine, so I can track down parts via sources other than Packard-Bell?"



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    Service Information

    Printer, copier, and fax Web sites

    Unfortunately, these tend to come and go! The following include some with info, error codes, message boards, and links. Some make their moeny on parts and repair kits to beware of those that may be overpriced.

    The links that used to be in this document have been removed since attempting to maintain two sets of nearly identical links (here and in my bookmark file), many with short half-lives, became unbearable. Therefore, please go to the "Printer/Photopier/Fax Sites/Information" sections of Sam's Neat, Nifty, and Handy Bookmarks.

    USENET newsgroups

    In addition to the USENET newsgroup: sci.electronics.repair, there are a variety of computer related newsgroups including comp.periphs.printer, comp.laser-printers, and comp.sys.hp.hardware which are relevant to printer related problems. However, sci.electronics.repair is probably still best for hardware type print problems (not drivers or applications).

    Copier forums

    This is a newsgroup style bulletin board for copier selection, troubleshooting, repair and appears to be a good archive if you should need to find something not in this document - hard to believe, but possible :-). However, it is separate and distinct from any Usenet affiliation as far as I can tell.

    HP LaserJet parts

    (From: Dave Lee (leedj@uwec.edu).)

    Dor HP Laser printers, try:

    Laser printer cartridge rebuild info

    (From: terwes11 (terwes11@email.msn.com).)

    I've been recycling cartridges for a few years now. Summit Laser Products (formerly Chenesko Products) has comprehensive product and technical information.

    Although they are not aimed at hobbyists and do-it-yourselfers their emphasis on service is refreshing. Currently their minimum order is $60 with about 6%discount above $250. They can probably point the private consumer to stores which do handle single-unit sales.

    Another distributor for the pro is Oasis Imaging (1-800-322-8992, New Hampshire for regional office).

    Here are a couple of places who used to handle small orders. I haven't been in touch with in years, though:

    Steven Michlin's LaserLand (orders 800-60-TONER) in Michigan Computer Friends (orders 800-547-3303) in Oregon had "starter kits"

    Finally, RECHARGER Magazine intended for the remanufacturing industry only. Each issue is full of products and companies.

    Printer parts

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    I've heard good things about a company called 'The PrinterWorks' for HP (and other Canon) laserprinter parts. They have a web page with an on-line catalog and search facility at:

    All kinds of parts are available even down to that little brush stored inside your HP LaserJet Series II: The SX engine parts catalogue shows that the part on page 350 (feeder assembly) as part number RF1-1177-000. It costs $1.23 plus shipping. Or, that 27/21 tooth fuser driver gear (RS1-0287-000). It costs $1.10 in quantities of 1.

    (From: Dave Lee (leedj@uwec.edu).)

    I have used them for the last 4-5 years for HP Laser and ink jet parts. They also do some Panasonic parts. Great tech support, good prices, same day shipping, etc. They have treated me very well. Also, service information on a variety of printers.

    (From: Paul Strider (pstrider@phys.ufl.edu).)

    (From: George Hurley (ghurley@voicenet.com).)

    They'll even fax or mail you a diagram of printer subassemblies so you can identify the exact part you need.

    (From: Dave Noseworthy (davenos@pesl.com).)

    Katum is a business machine (i.e., copier/fax/page printer, etc.) part supplier to office equipment dealers. If they won't sell direct to you, I'm sure they'll indicate a local dealer.

    (From: SargW1 (sargw1@aol.com).)

    (From: Sid Ashen-Brenner (sashen@midusa.net).)

    You may be able to get a Service Sheet with the error codes (among other information). They also sell parts & supplies.

    HP DeskJet Parts

    (From: Jeff (jkinc@erols.com).)

    Try this link for HP and other printer parts:

    They have a free tech line. Much better than HP.

    LaserJet II: Where is the fuse?

    (From: Tony Duell (ard@p850ug1.demon.co.uk).)

    There are 3 fuses/breakers to my knowledge:

    The mains circuit breaker is in the AC block (right hand side of the fuser). It's hidden by the fan duct, but that's quite easy to remove if you have the casing off. The breaker is a little rectangular object with a button on top, on the lower PCB. Press down the button and try again.

    The Low Voltage PSU contains the other 2 fuses. One is in the mains side, and is a normal 20mm cartridge fuse. If you remove the casing and the bracket round the front of the printer (6 screws), you can see this fuse on the PSU PCB. This fuse is a listed spare part at 'the Printerworks', which is strange, since the only time it should fail is if there's something majorly wrong with the PSU, and no other PSU spares are available.

    The other fuse is a thermal one, clamped to the heatsink in the top right corner of the PSU PCB (looking at it from the component side). This one protects the 24 V pass transistor that on the same heatsink. I've never had to replace this one, so I don't know what the rating is.

    If all the fuses are good, then you need to do some more troubleshooting. Firstly, check for mains at the 2-wire connector to the LV PSU. If that's missing, then you need to remove the mains input block (easy, once you've removed the fuser), and sort it out. It's _very_ simple, and should pose no problems.

    If mains is present at the input to the LV PSU, check its outputs. Remove the base cover, and sit the printer on the right hand side. The LV PSU output is on the 14 pin connector in the middle of the engine control (DC controller) PCB. The front 2 pins are ground, the next 2 are +5 V, and the rearmost one is +24 V. If they're missing, you have a PSU problem.

    Good luck in that case - Canon flatly refused to supply me with any spares for the PSU. They claimed that it would be dangerous to repair it. Quite why it's more dangerous than any other SMPS that I've worked on remains to be seen.

    LaserJet III: Where is the fuse?

    "I am looking for the fuse of an HP LJ III. I shorted an exposed wire to ground at the fuser unit with my screwdriver. It was exposed because someone broke the cover of the fuser unit. Now the printer gets no power, the front display does not light, the fan does not come on. I looked for the fuse in all obvious places to no avail. Any hint is appreciated.

    (From: Patrick Mulvey (pmulvey@li.net).)

    A number of the fuses that are in the laserjets are hard to spot. There is a small component on the boards that is a small black disk. You will have to follow the wiring from the fuser back to the board and look for this small component (fuse). I have on one occasion lost power to the paper feed motors installing a card access device (defective harness shorted the motor to ground), and found the "fuse" after looking everywhere. Looks like a disk cap but leads are on opposite side of the disk and its mounted parallel to the PCB. Hope this helps...

    Copier and laser printer manuals

    (From: Gerald Chafee (GChafee@worldnet.att.net).)

    I have had good luck purchasing manuals from a company called "Wright-Moore Corp, P.O. Box, 66019, Indianapolis, IN. 46266-6019. I have bought a ton of Toshiba parts and manuals for less than a quarter what any Toshiba repair parts distributor quotes and I know that they are a distributor for Mita. The only possible problem is that they want to deal with someone that has a business license (read resale or Tax ID certificate). If you know someone that will let you use their name and / or address, Wright-Moore doesn't care if it is copier or laser printer connected. They do have an 800 number which I don't have in front of me but is listed with 800 directory assistance.

    Canon information

    Canon has a faxback service at 1-800-526-4345. Quite a bit of technical information is apparently available for their printers.

    Epson printer switch settings

    (From: Kim (103114.1526@compuserve.com).) Some info can be found at:

    Hewlett Packard information

    HP actually has a fair amount of printer maintenance and troubleshooting information on-line but no schematics:

    Printer schematics?

    "Working "on my own" Okidata microline 590. Need a print of mother PCB and regulator PCB. A copy of the schematic will save time and let this OLD TV tech enjoy life.... Thanks"

    (From: Joe Wagg (jwagg@fs.cei.net).)

    Good luck. Even the Okidata service manuals don't have schematics. The easiest and most cost effective way I know to fix these printers is to send the board off to be repaired. I'm not sure about the price, but the logic board for that model is probably around $100, assuming you send yours in to be repaired. This way you get a known good board with a guarantee. I suggest using Laser Impact, address below. Hope this helps.

    (From: Uncle Monster (unclemon@bellsouth.net).)

    Try "Ted Dasher & Associates" (http://www.dasher.com), 1-800-638-4833. Ted sells refurbished HP equipment out of Birmingham, AL, He may sell you the parts, info or a trashed printer with the parts you need.

    References

    (From: Franc Zabkar.)

    The Copier, Printer, Fax and MFC Cross Reference Guide may be helpful in determining if an OEM machine is the same as a machine sold under a private label, or vice versa.

    Here is the start of a list....

    1. Maintain and Repair Your Computer Printer and Save a Bundle
      Stephen J, Bigelow
      Wincrest/TAB Books, a division of McGraw-Hill, 1992
      ISBN 0-8306-2563-2, ISBN 0-8306-3507-6 (paperback).

    2. Easy Laser Printer Maintenance and Repair
      Bigelow et. al.
      Windcrest Publishing
      ISBN: 0070359768



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