Notes on the Troubleshooting and Repair of Small Household Appliances and Power Tools

Preface

Author and Copyright

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Copyright © 1994-2008
All Rights Reserved

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

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DISCLAIMER

Improper repair of battery operated devices can also result in bad consequences for you, the device, and any equipment attached to it.

We will not be responsible for damage to equipment, your ego, county wide power outages, spontaneously generated mini (or larger) black holes, planetary disruptions, or personal injury or worse that may result from the use of this material.

Introduction

Where do you keep your dead appliances?

However, if you can do the repair yourself, the equation changes dramatically as your parts costs will be 1/2 to 1/4 of what a professional will charge and of course your time is free. The educational aspects may also be appealing. You will learn a lot in the process. Many problems can be solved quickly and inexpensively. Fixing an old vacuum cleaner to keep in the rec room may just make sense after all.

This document provides maintenance and repair information for a large number of small household appliances and portable power tools. The repair of consumer electronic equipment is dealt with by other documents in the "Notes on the Troubleshooting and Repair of..." series. Suggestions for additions (and, of course, correction) are always welcome.

You will be able to diagnose problems and in most cases, correct them as well. Most problems with household appliances are either mechanical (e.g., dirt, lack of or gummed up lubrication, deteriorated rubber parts, broken doohickies) or obvious electrical (e.g., broken or corroded connections, short circuits, faulty heating elements) in nature. With minor exceptions, specific manufacturers and models will not be covered as there are so many variations that such a treatment would require a huge and very detailed text. Rather, the most common problems will be addressed and enough basic principles of operation will be provided to enable you to narrow the problem down and likely determine a course of action for repair. In many cases, you will be able to do what is required for a fraction of the cost that would be charged by a repair center - or - be able to revive something that would otherwise have gone into the dumpster - or remained in that closet until you moved out of your house (or longer)!

Since so many appliances are variations on a theme - heating, blowing, sucking, rotating, etc. - it is likely that even if your exact device does not have a section here, a very similar one does. Furthermore, with your understanding of the basic principles of operation, you should be able to identify what is common and utilize info in other sections to complete a repair.

Should you still not be able to find a solution, you will have learned a great deal and be able to ask appropriate questions and supply relevant information if you decide to post to sci.electronics.repair (recommended), alt.home.repair, or misc.consumers.house. It will also be easier to do further research using a repair textbook. In any case, you will have the satisfaction of knowing you did as much as you could before finally giving up or (if it is worthwhile cost-wise) taking it in for professional repair. With your newly gathered knowledge, you will have the upper hand and will not easily be snowed by a dishonest or incompetent technician.

Some Tidbits

• Virtually any table lamp can be restored to a like-new condition electrically for less than $5 in parts.

• The cause of a vacuum cleaner that starts blowing instead of sucking is likely a dirt clog somewhere. It is virtually impossible for the motor to spin in the wrong direction and even if it did, the vacuum would still have some suction due to the type of blower that is commonly used.

• Many diagnoses of burned out motors are incorrect. Very often motor problems are actually something else - and minor. A truly burned out motor will often have died spectacularly and under adverse conditions. It will likely be smelly, charred, or may have created lots of sparks, tripped a circuit breaker or blew a fuse. A motor that just stopped working may be due to worn or gummed up (carbon) brushes, dirt, or a fault elsewhere in the appliance like a bad connection or switch or circuit - or the AC outlet might be bad. The most likely cause of a vacuum cleaner or other similar appliance that just stopped working is a break in a wire of the power cord - probably at the plug - due to continual stress from being dragged around by its tail!

• Fluorescent lamps use only 1/3 to 1/2 of the power of an incandescent lamp of similar light output. With all the lighting used in an average household, this can add up particularly for high power ceiling fixtures. However, fluorescent light color and quality may not be as aesthetically pleasing and fixtures or lamps may produce Radio Frequency Interference (RFI) causing problems with TV or radio reception. Dimmers can usually not be used unless they are specifically designed for fluorescent fixtures. Compact fluorescent lamps do indeed save energy but they can break just like any other light bulb!

• The initial inrush current to an incandescent bulb may be 10 times the operating current. This is hard on switches and dimmers and is part of the reason behind why bulbs tend to burn out when switched on and not while just sitting there providing illumination. Furthermore, an erratic switch or loose connection can shorten the life of an incandescent bulb due to repeated thermal shock. And, these are not due to short circuits but bad intermittent connections. True short circuits are less common and should result in a blown fuse or tripped circuit breaker.

• Bulb Savers and other devices claiming to extend the life of incandescent light bulbs may work but do so mostly by reducing power to the bulb at the expense of some decrease in light output and reduced efficiency. It is estimated that soft start alone (without the usual associated reduction in power) does not prolong the life of a typical bulb by more than a few hours.

  Thus, in the end, these device increase costs if you need to use more or larger bulbs to make up for the reduced light output. The major life cycle expense for incandescent lighting is not the cost of the bulbs but the cost of the electricity - by a factor of 25 to 50! For example, it costs about $10 in electricity to run a 100 W bulb costing 25 cents over the course of its 1000 hour life. However, these devices (or the use of 130 V bulbs) may make sense for use in hard-to-reach locations. Better yet, consider compact or normal fluorescent bulbs or fixtures which last much longer and are much more efficient than incandescents (including halogen).

• Smart bulbs are legitimate technology with built in automatic off, dimmers, blink capability, and other 'wizzy' features but they burn out and break just like ordinary bulbs. Thus, it hardly makes sense to spend $5 to $10 for something that will last 1000 to 1500 hours. Install a proper dimmer, automatic switch, or external blinker instead.

• A Ground Fault Circuit Interrupter (GFCI) protects people against shock but does not necessarily protect appliances from damage due to electrical faults. This is the function of fuses, circuit breakers, and thermal protectors. A GFCI *can* generally be installed in place of a 2-wire ungrounded outlet to protect it and any outlets downstream. Check your local electrical Code to be sure if this is permitted.

• Don't waste your money on products like the 'Green Plug', magnetic water softeners, whole house TV antennas that plug into the wall socket, and other items of the "it sounds too good to be true' variety. These are very effective only at transferring money out of your wallet but rarely work as advertised.
  • The Green Plug will not achieve anywhere near the claimed savings and may actually damage or destroy certain types of appliances like, guess what?: refrigerators and other induction motor loads. Ever seen the demo?

    The Green Plug is supposed to reduce reactive power (V and I out of phase due to inductive or capacitive loads) but residential users don't pay for reactive power anyway, only the real power they use. In addition, this is a minor concern for modern appliances.

    The demo you see in the store that shows a utility meter slowing down substantially when the Green Plug is put in the circuit is bogus for two reasons: (1) The motor being powered is totally unloaded resulting in a high ratio of reactive to real power. Under normal use with a motor driving a load, the reduction in electricity use would be negligible. (2) The meter is wired to include reactive power in its measurement which, as noted above, is not the case with residential customers.

  • Magnetic and radio frequency water softeners are almost certainly 100% scams. They cloak absolutely useless technology in so much 'technobabble' that even Ph.D. scientists and engineers have trouble sorting it all out. The latest wrinkle adds advanced microprocessor control optimized for each potential mineral deposit. Yeh, sure.

    Mention the word 'magnetism' and somehow, people will pay $300 for $2 worth of magnets that do nothing - and then be utterly convinced of their effectiveness. They forget that perhaps the instruction manual suggested changes in their water use habits - which was the true reason for any improvement. Perhaps the magnets can be used to stick papers on the refrigerator once you discover they don't do anything for the water.

    BTW, the same goes for magnetic wine flavor enhancers. :-)

  • Whole house TV antennas are great for picking up signals with ghosts, noise, and other distorting effects. The premise that 'more is better' is fundamentally flawed when it comes to TV reception. In rare cases they may produce a marginally viewable picture in an otherwise unfavorable location but these are the exceptions. A pair of set-top rabbit ears will generally be superior.

I will be happy to revise these comments if someone can provide the results of evaluations of any of these devices conducted by a recognized independent testing laboratory. However, I won't hold my breath waiting.

Basic Appliance Theory

What is inside an appliance?

• Heating - a resistance element similar to what you can see inside a toaster provides heat to air, liquids, or solids by convections, conduction, or direct radiant (IR) heat.

• Rotation, blowing, sucking - a motor provides power to move air as in a fan or vacuum cleaner, water as in a sump pump, or provide drive as in an electric pencil sharpener, food mixer, or floor polisher.

• Control - switches and selectors, thermostats and speed regulators, and microcomputers determine what happens, when, how much, and assure safe operation.

Basic electrical principles

Voltage, current, and resistance

The easiest way to explain basic electrical theory without serious math is with a hydraulic analogy. This is of the plumbing system in your house:

Water is supplied by a pipe in the street from the municipal water company or by a ground water pump. The water has a certain pressure trying to push it through your pipes. With electric circuits, voltage is the analog to pressure. Current is analogous to flow rate. Resistance is analogous the difficulty in overcoming narrow or obstructed pipes or partially open valves.

Intuitively, then, the higher the voltage (pressure), the higher the current (flow rate). Increase the resistance (partially close a valve or use a narrower pipe) and for a fixed voltage (constant pressure), the current (flow rate) will decrease.

With electricity, this relationship is what is known as linear: double the voltage and all other factors remaining unchanged, the current will double as well. Increase it by a factor of 3 and the current will triple. Halve the resistance and for a constant voltage source, the current will double. (For you who are hydraulic engineers, this is not quite true with plumbing as turbulent flow sets in, but this is just an analogy, so bear with me.)

Note: for the following 4 items whether the source is Direct Current (DC) such as a battery or Alternating Current (AC) from a wall outlet does not matter. The differences between DC and AC will be explained later.

The simplest electrical circuit will consist of several electrical components in series - the current must flow through all of them to flow through any of them. Think of a string of Christmas lights - if one burns out, they all go out because the electricity cannot pass through the broken filament in the burned out bulb.

Note the term 'circuit'. A circuit is a complete loop. In order for electricity to flow, a complete circuit is needed.

                          Switch (3)
               _____________/ ______________
              |                             |
              | (1)                         | (4)
      +-------+--------+                +---+----+
      |  Power Source  |                |  Load  |
      +-------+--------+                +---+----+
              |            Wiring (2)       |
              |_____________________________|

1. Power source - a battery, generator, or wall outlet. The hydraulic equivalent is a pump or dam (which is like a storage battery). The water supply pipe in the street is actually only 'wiring' (analogous to the electric company's distribution system) from the water company's reservoir and pumps.

2. Conductors - the wiring. Similar to pipes and aqueducts. Electricity flows easily in good conductors like copper and aluminum. These are like the insides of pipes. To prevent electricity from escaping, an insulator like plastic or rubber is used to cover the wires. Air is a pretty good insulator and is used with high power wiring such as the power company's high voltage lines but plastic and rubber are much more convenient as they allow wires to be bundled closely together.

3. Switch - turns current on or off. These are similar to valves which do not have intermediate positions, just on and off. A switch is not actually required in a basic circuit but will almost always be present.

4. Load - a light bulb, resistance heater, motor, solenoid, etc. In true hydraulic systems such as used to control the flight surfaces of an aircraft, there are hydraulic motors and actuators, for example.

   With household water we usually don't think of the load. However, things like lawn sprinklers, dishwasher rotating arms, pool sweepers, and the like do convert water flow to mechanical work in the home (some homes, at least!). Hydraulic motors are used to aircraft and spacecraft, large industrial robots, and all sorts of other applications.

Here are 3 of the simplest appliances:

• Flashlight: battery (1), case and wiring (2), switch (3), light bulb (4).

• Table lamp: wall outlet (1), line cord and internal wiring (2), power switch (3), light bulb (4).

• Electric fan, vacuum cleaner, garbage disposer: wall outlet (1), line cord and internal wiring (2), power switch (3), motor (4).

Now we can add one type of simple control device:

5. Thermostat - a switch that is sensitive to temperature. This is like an automatic water valve which shuts off if a set temperature is exceeded. Most thermostats are designed to open the circuit when a fixed or variable temperature is exceeded. However, air conditioners, refrigerators, and freezers do the opposite - the thermostat switches on when the temperature goes too high. Some are there only to protect against a failure elsewhere due to a bad part or improper use that would allow the temperature to go too high and start a fire. Others are adjustable by the user and provide the ability to control the temperature of the appliance.

With the addition of a thermostat, many more appliances can be constructed including (this is a small subset):

• Electric space heater (radiant), broiler, waffle iron: wall outlet (1), line cord and internal wiring (2), power switch (3) and/or thermostat (5), load (heavy duty heating element).

• Electric heater (convection), hair dryer: wall outlet (1), line cord and internal wiring (2), power switch (3) and/or thermostat (5), loads (4) (heating element and motor).

Electric heaters and cooking appliances usually have adjustable thermostats.

Hair dryers may simply have several settings which adjust heater power and fan speed (we will get into how later). The thermostat may be fixed and to protect against excessive temperatures only.

That's it! You now understand the basic operating principle of nearly all small appliances. Most are simply variations (though some may be quite complex) on these basic themes. Everything else is just details.

For example, a blender with 38 speeds just has a set of buttons (switches) to select various combinations of motor windings and other parts to give you complete control (as if you need 38 speeds!). Toasters have a timer or thermostat activate a solenoid (electromagnet) to pop your bread at (hopefully) the right time.

6. Resistances - both unavoidable and functional. Except for superconductors, all materials have resistance. Metals like copper, aluminum, silver, and gold have low resistance - they are good conductors. Many other metals like iron or steel are fair but not quite as good as these four. One, NiChrome - an alloy of nickel and chromium - is used for heating elements because it does not deteriorate (oxidize) in air even at relatively high temperatures.

   A significant amount of the power the electric company produces is lost to heating of the transmission lines due to resistance and heating.

   However, in an electric heater, this is put to good use. In a flashlight or table lamp, the resistance inside the light bulb gets so hot that it provides a useful amount of light.

   A bad connection or overloaded extension cord, on the other hand, may become excessively hot and start a fire.

The following is more advanced - save for later if you like.

7. Capacitors - energy storage devices. These are like water storage tanks (and similar is some ways to rechargeable batteries). Or, a system consisting of a a rubber diaphragm separating the water from a volume of trapped air. As water is pumped in, energy is stored as the air is compressed as in the captive air or expansion tanks found in home heating systems or well water storage tanks.

   Capacitors are not that common in small appliances but may be used with some types of motors and in RFI - Radio Frequency Interference - filters as capacitors can buffer - bypass - interference to ground. The energy to power an electronic flash unit is stored in a capacitor, for example. Because they act like reservoirs - buffers - capacitors are found in the power supplies of most electronic equipment to smooth out the various DC voltages required for each device.

8. Inductors - their actual behavior is like the mass of water as it flows. Turn off a water faucet suddenly and you are likely to hear the pipes banging or vibrating. This is due to the inertia of the water - it tends to want to keep moving. Electricity doesn't have inertia but when wires are wound into tight coils, the magnetic field generated by electric current is concentrated and tends to result in a similar effect. Current tends to want to continue to flow where inductance is present. (For the more technical reader, the air chamber used to prevent/minimize the water hammer effect is the equivalent of an RC snubber!)

   The windings of motors and transformers have significant inductance but the use of additional inductance devices is rare in home appliances except for RFI - since inductance tends to prevent current from changing, it can also be used to prevent interference from getting in or out.

9. Controls - rheostats and potentiometers allow variable control of current or voltage. A water faucet is like a variable resistor which can be varied from near 0 ohms (when on fully) to infinite ohms (when off).

Ohm's Law

The simplest of these are:

                    V = I * R (1)
                    I = V / R (2) 
                    R = V / I (3)

• V is Voltage in Volts (or millivolts - mV or kilovolts - kV).
• I is current in amperes (A) or milliamps (mA)
• R is resistance in Ohms (ohms), kilo-Ohms (K Ohms), or mega-Ohms (M Ohms).

                    P = V * I      (4)
                    P = V * V / R  (5)
                    P = I * I * R  (6)

• For a flashlight with a pair of Alkaline batteries (3 V) and a light bulb with a resistance of 10 ohms, we can use (2) to find that the current is I = (3 V) / (10 ohms) = .3 A. The from (4) we find that the power is: P = (3 V * .3 A) = .9 W.

• For a blow-dryer rated at 1000 W, the current drawn from a 120 V line would be: I = P / V (by rearranging (4) = 1000 W / 120 V = 8.33 A.

• Increase voltage -> higher current. (If the water company increases the pressure, your shower used more water in a given time.)

• Decrease resistance -> higher current. (You have a new wider pipe installed between the street and your house. Or, you open the shower valve wider.)

DC and AC

A direct current source is at a constant voltage. Displaying the voltage versus time plot for such a source would show a flat line at a constant level. Some examples:

• Alkaline AA battery - 1.5 V (when new).
• Automotive battery - 12 V (fully charged).
• Camcorder battery - 7.2 V (charged).
• Discman AC adapter - 9 VDC (fully loaded).
• Electric knife AC adapter - 3.6 VDC.

The nominal voltage from an AC outlet in the U.S. is around 115 VAC. This is the RMS (Root Mean Square) value, not the peak (0 to maximum). In simple terms, the RMS value of an AC voltage and the same value of a DC voltage will result in identical heating (power) to a resistive load. For example, 115 VAC RMS will result in the same heat output of a broiler as 115 VDC.

Direct current is used for many small motor driven appliances particularly when battery power is an option since changing DC into AC requires some additional circuitry. All electronic equipment require various DC voltages for their operation. Even when plugged into an AC outlet, the first thing that is done internally (or in the AC adapter in many cases) is to convert the AC to various DC voltages.

The beauty of AC is that a very simple device - a transformer - can convert one voltage into another. This is essential to long distance power distribution where a high voltage and low current is desirable to minimize power loss (since it depends on the current). You can see transformers atop the power poles in your neighborhood reducing the 2,000 VAC or so from a local distribution transformer to your 115 VAC (actually, 115-0-115 were the total will be used by large appliances like electric ranges and clothes dryers). That 2,000 VAC was stepped down by a larger transformer from around 12,000 VAC provided by the local substation. This, in turn, was stepped down from the 230,000 VAC or more used for long distance electricity transmission. Some long distance lines are over 1,000,000 volts (MV).

When converting between one voltage and another with a transformer, the amount of current (amps) changes in the inverse ratio. So, using 230 kV for long distance power transmission results in far fewer heating losses as the current flow is reduced by a factor of 2,000 over what it would be if the voltage was only 115 V, for example. Recall that power loss from P=I*I*R is proportional to the square of the current and thus in this example is reduced by a factor of 4,000,000!

Many small appliances include power transformers to reduce the 115 VAC to various lower voltages used by motors or or electrical components. Common AC adapters - often simply called transformers or wall warts - include a small transformer as well. Where their output is AC, this is the only internal component other than a fuse or thermal fuse for protection. Where their output is DC, additional components convert the low voltage AC from the transformer to DC and a capacitor smoothes it out.

Series and parallel circuits

The loads, say resistance heating elements, are now drawn with the schematic symbol (as best as can be done using ASCII) for a resistor.

                          Switch
               _____________/ __________________
              |                 I -->           |
              |                        ^    ^   |
              |                        |    |   / R1
              |                        |   V1   \ Load 1
      +-------+--------+               |    |   /
      |  Power Source  |                    v__ |
      +-------+--------+              V(S)  ^   |
              |                             |   / R2
              |                        |   V2   \ Load 2
              |                        |    |   /
              |                        v    v   |
              |_________________________________|

                    R(T) = R1 + R2                (7)

                    V1 = V(S) * R1 / (R1 + R2)    (8)
                    V2 = V(S) * R2 / (R1 + R2)    (9)

                    I = V(S)  / (R1 + R2)        (10)

                          Switch
               _____________/ ___________________________
              |                      I -->  |            |
              |                 ^           |            |
      +-------+--------+        |           / R1         / R2
      |  Power Source  |       V(S)         \ Load 1     \ Load 2
      +-------+--------+        |           /            /
              |                 v           |v I(1)      |v I(2)
              |_____________________________|____________|

The total resistance, R(T), of the parallel resistors in this circuit is:

                    R(T) = (R1 * R2) / (R1 + R2)  (11)

                    I1 = V(S)/R1                  (12)
                    I2 = V(S)/R2                  (13)

                    I = I1 + I2                   (14)

On-line educational resources

Check out Sam's Neat, Nifty, and Handy Bookmarks in the "Education and Tutorials" area for links to introductory material on electronics and other related fields.

Appliance Troubleshooting

SAFETY

However, AC line power can be lethal. Proper safety procedures must be followed whenever working on live equipment (as well as devices which may have high energy storage capacitors like TVs, monitors, and microwave ovens). AC line power due to its potentially very high current is actually considerably more dangerous than the 30 kV found in a large screen color TV!

These guidelines are to protect you from potentially deadly electrical shock hazards as well as the equipment from accidental damage.

Note that the danger to you is not only in your body providing a conducting path, particularly through your heart. Any involuntary muscle contractions caused by a shock, while perhaps harmless in themselves, may cause collateral damage - there are many sharp edges inside this type of equipment as well as other electrically live parts you may contact accidentally.

Safety myths

You may have heard warnings about dangers from unplugged appliances. Perhaps, these were passed down from your great great grandparents or from local bar room conversation.

Except for devices with large high voltage capacitors connected to the line or elsewhere, there is nothing inside an appliance to store a painful or dangerous charge. Even these situations are only present in microwave ovens, fluorescent lamps and fixtures with electronic ballasts, universal power packs for camcorders or portable computers, or appliances with large motors. Other than these, once an appliance is unplugged all parts are safe to touch - electrically that is. There may still be elements or metal brackets that are burning hot as metal will tend to retain heat for quite a while in appliances like toasters or waffle irons. Just give them time to cool. There are often many sharp edges on sheetmetal as well. Take your time and look before you leap or grab anything.

Note that this list of dangerous appliances doesn't include CRT-type TVs, computer monitors, and other similar electronic equipment - which most certainly can store a dangerous charge on the CRT long after being unplugged - only because they aren't normally considered appliances. :)

Safety guidelines

• Don't work alone - in the event of an emergency another person's presence may be essential.

• Always keep one hand in your pocket when anywhere around a powered line-connected or high voltage system.

• Wear rubber bottom shoes or sneakers.

• Wear eye protection - large plastic lensed eyeglasses or safety goggles.

• Don't wear any jewelry or other articles that could accidentally contact circuitry and conduct current, or get caught in moving parts.

• Set up your work area away from possible grounds that you may accidentally contact.

• Know your equipment: small appliances with 2 prong plugs do not use any part of the outside case for carrying current. Any metal parts of the case will either be totally isolated or possibly connected to one side of the line through a very high value resistor and/or very low value capacitor. However, there may be exceptions. And, failures may occur. Appliances with 3 prong plugs will have the case and any exposed metal parts connected to the safety ground.

• If circuit boards or other subassemblies need to be removed from their mountings, put insulating material between them and anything they may short to. Hold them in place with string or electrical tape. Prop them up with insulation sticks - plastic or wood.

• Parts of heating appliances can get very hot very quickly. Always carefully test before grabbing hold of something you will be sorry about later.

• If you need to probe, solder, or otherwise touch circuits with power off, discharge (across) large power supply filter capacitors with a 2 W or greater resistor of 100-500 ohms/V approximate value (e.g., for a 200 V capacitor use a 50 K ohm resistor). The only places you are likely to find large capacitors in small appliance repair are in induction motor starting or running circuitry or the electronic ballasts of fluorescent fixtures.

• Connect/disconnect any test leads with the equipment unpowered and unplugged. Use clip leads or solder temporary wires to reach cramped locations or difficult to access locations.

• Perform as many tests as possible with the device unplugged. Even with the power switch supposedly off, if the unit is plugged into a live outlet, line voltage may be present in unexpected places or probing may activate a motor due to accidentally pressing a microswitch. Most parts in household appliances and power tools can be can be tested using only an ohmmeter or continuity checker.

• If you must probe live, put electrical tape over all but the last 1/16" of the test probes to avoid the possibility of an accidental short which could cause damage to various components. Clip the reference end of the meter or scope to the appropriate ground return so that you need to only probe with one hand.

• Use an isolation transformer if there is any chance of contacting line connected circuits. A Variac(tm) is not an isolation transformer!

  The use of a GFCI (Ground Fault Circuit Interrupter) protected outlet is a good idea but will not protect you from shock from many points in a line connected TV or monitor, or the high voltage side of a microwave oven, for example. (Note however, that, a GFCI may nuisance trip at power-on or at other random times due to leakage paths (like your scope probe ground) or the highly capacitive or inductive input characteristics of line powered equipment.) A fuse or circuit breaker is too slow and insensitive to provide any protection for you or in many cases, your equipment. However, these devices may save your scope probe ground wire should you accidentally connect it to a live chassis.

• Don't attempt repair work when you are tired. Not only will you be more careless, but your primary diagnostic tool - deductive reasoning - will not be operating at full capacity.

• Finally, never assume anything without checking it out for yourself! Don't take shortcuts!

Should I unplug appliances when not in use?

BTW, electronic equipment should always be unplugged during lightning storms since it may be very susceptible to power surge and lightning damage. Don't forget the telephones and computer modems as well. This is not as much of a problem with small appliances that do not include electronic controllers as except for direct lightning strikes, the power switch will provide protection.

Troubleshooting tips

If you get stuck, sleep on it. Sometimes, just letting the problem bounce around in your head will lead to a different more successful approach or solution. Don't work when you are really tired - it is both dangerous and mostly non-productive (or possibly destructive - especially with AC line powered appliances).

Whenever working on precision equipment, make copious notes and diagrams. Yes, I know, a toaster may not exactly be precision equipment, but trust me. You will be eternally grateful when the time comes to reassemble the unit. Most connectors are keyed against incorrect insertion or interchange of cables, but not always. Apparently identical screws may be of differing lengths or have slightly different thread types. Little parts may fit in more than one place or orientation. Etc. Etc.

Pill bottles, film canisters, and plastic ice cube trays come in handy for sorting and storing screws and other small parts after disassembly.

Select a work area which is well lighted and where dropped parts can be located - not on a deep pile shag rug. Something like a large plastic tray with a slight lip may come in handy as it prevents small parts from rolling off of the work table. The best location will also be relatively dust free and allow you to suspend your troubleshooting to eat or sleep or think without having to pile everything into a cardboard box to eat dinner.

Basic hand tools

An electric drill or drill press with a set of small (1/16" to 1/4") high quality high speed drill bits is handy for some types of restoration where new holes need to be provided. A set of machine screw taps is also useful at times.

A medium power soldering iron and rosin core solder (never never use acid core solder or the stuff for sweating copper pipes on electrical or electronic repairs!) will be required if you need to make or replace any soldered connections. A soldering gun is desirable for any really beefy soldering. See the section: Soldering techniques.

A crimping tool and an assortment of solderless connectors often called 'lugs' will be needed to replace damaged or melted terminals in small appliances. See the section: Solderless connectors.

Old dead appliances can often be valuable sources of hardware and sometimes even components like switches and heating elements. While not advocating being a pack rat, this does have its advantages at times.

Soldering techniques

Use of the proper technique is critical to reliability and safety. A good solder connection is not just a bunch of wires and terminals with solder dribbled over them. When done correctly, the solder actually bonds to the surface of the metal (usually copper) parts.

CAUTION: You can easily turn a simple repair (e.g., bad solder connections) into an expensive mess if you use inappropriate soldering equipment and/or lack the soldering skills to go along with it. If in doubt, find someone else to do the soldering or at least practice, practice, practice, soldering and desoldering on a junk unit first!

Effective soldering is by no means difficult but some practice may be needed to perfect your technique.

The following guidelines will assure reliable solder joints:

• Only use rosin core solder (e.g., 60/40 tin/lead) for electronics work. A 1 pound spool will last a long time and costs about $10. Suggested diameter is .030 to .060 inches for appliances. The smaller size is preferred as it will be useful for other types of precision electronics repairs or construction as well. The rosin is used as a flux to clean the metal surface to assure a secure bond. NEVER use acid core solder or the stuff used to sweat copper pipes! The flux is corrosive and it is not possible to adequately clean up the connections afterward to remove all residue.

• Keep the tip of the soldering iron or gun clean and tinned. Buy tips that are permanently tinned - they are coated and will outlast countless normal copper tips. A quick wipe on a wet sponge when hot and a bit of solder and they will be as good as new for a long time. (These should never be filed or sanded).

• Make sure every part to be soldered - terminal, wire, component leads - is free of any surface film, insulation, or oxidation. Fine sandpaper or an Xacto knife may be used, for example, to clean the surfaces. The secret to a good solder joint is to make sure everything is perfectly clean and shiny and not depend on the flux alone to accomplish this. Just make sure the scrapings are cleared away so they don't cause short circuits.

• Start with a strong mechanical joint. Don't depend on the solder to hold the connection together. If possible, loop each wire or component lead through the hole in the terminal. If there is no hole, wrap them once around the terminal. Gently anchor them with a pair of needlenose pliers.

• Use a properly sized soldering iron or gun: 20-25 W iron for fine circuit board work; 25-50 W iron for general soldering of terminals and wires and power circuit boards; 100-200 W soldering gun for chassis and large area circuit planes. With a properly sized iron or gun, the task will be fast - 1 to 2 seconds for a typical connection - and will result in little or no damage to the circuit board, plastic switch housings, insulation, etc. Large soldering jobs will take longer but no more than 5 to 10 seconds for a large expanse of copper. If it is taking too long, your iron is undersized for the task, is dirty, or has not reached operating temperature. For appliance work there is no need for a fancy soldering station - a less than $10 soldering iron or $25 soldering gun as appropriate will be all that is required.

• Heat the parts to be soldered, not the solder. Touch the end of the solder to the parts, not the soldering iron or gun. Once the terminal, wires, or component leads are hot, the solder will flow via capillary action, fill all voids, and make a secure mechanical and electrical bond. Sometimes, applying a little from each side will more effectively reach all nooks and crannies.

• Don't overdo it. Only enough solder is needed to fill all voids. The resulting surface should be concave between the wires and terminal, not bulging with excess solder.

• Keep everything absolutely still for the few seconds it takes the solder to solidify. Otherwise, you will end up with a bad connection - what is called a 'cold solder joint'.

• A good solder connection will be quite shiny - not dull gray or granular. If your result is less than perfect reheat it and add a bit of new solder with flux to help it reflow.

Desoldering techniques

See the document: Troubleshooting and Repair of Consumer Electronic Equipment for additional info on desoldering of electronic components.

Soldering pins in plastic connectors

One approach that works in some cases is to use the mating socket to stabilize the pins so they remain in position as you solder. The plastic will still melt - not as much if you use an adequately sized iron since the socket will act as a heat sink - but will not move.

An important consideration is using the proper soldering iron. In some cases, a larger iron is better - you get in and out more quickly without heating up everything in the neighborhood.

Solderless connectors

WireNuts allow multiple wires to be joined by stripping the ends and then 'screwing' an insulated thimble shaped plastic nut onto the grouped ends of the wires. A coiled spring (usually) inside tightly grips the bare wires and results in a mechanically and electrically secure joint. For appliance repair, the required WireNuts will almost always already be present since they can usually be reused. If you need to purchase any, they come in various sizes depending on the number and size of the wires that can be handled. It is best to twist the individual conductor strands of each wire together and then twist the wires together slightly before applying the WireNut.

Crimped connectors, called lugs, are very common in small appliances. One reason is that it is easier, faster, and more reliable, to make connections using these lugs with the proper crimping equipment than with solder.

A lug consists of a metal sleeve which gets crimped over one or more wires, an insulating sleeve (usually, not all lugs have these), and a terminal connection: ring, spade, or push-on are typical.

Lugs connect one or more wires to the fixed terminals found on switches, motors, thermostats, and so forth.

There are several varieties:

• Ring lugs - the end looks like an 'O' and must be installed on a threaded terminal of similar size to the opening in the ring. The screw or nut must be removed to replace a ring lug.

• Spade lugs - the end looks like a 'U' and must be installed on a threaded terminal of similar size to the opening in the spade. These can be slipped on and off without entirely removing the screw or nut.

• Push-on lugs - called 'FastOns' by one manufacturer. The push-on terminal makes a tight fit with a (usually) fixed 'flag'. There may also be a latch involved but usually just a pressure fit keeps the connection secure. However, excessive heat over time may weaken these types of connections, resulting in increased resistance, additional heating, and a bad connection or melt-down.

In the factory, the lugs are installed on the wires with fancy expensive equipment. For replacements, an inexpensive crimping tool and an assortment of lugs will suffice. The crimping tool looks like a pair of long pliers and usually combines a wire stripper and bolt cutter with the crimping function. It should cost about $6-10.

The crimping tool 'squashes' the metal sleeve around the stripped ends of the wires to be joined. A proper crimp will not come apart if an attempt is made to pull the wires free - the wires will break somewhere else first. It is gas-tight - corrosion (within reason) will not affect the connection.

Crimping guidelines:

• Use the proper sized lug. Both the end that accepts the wire(s) and the end that screws or pushes on must be sized correctly. Easiest is to use a replacement that is identical to the original. Where this is not possible, match up the wire size and terminal end as closely as possible. There will be a minimum and maximum total wire cross sectional area that is acceptable for each size. Avoid the temptation to trim individual conductor strands from wires that will not fit - use a larger size lug. Although not really recommended, the bare wires can be doubled over to thicken them for use with a lug that is slightly oversize.

• For heating appliances, use only high temperature lugs. This will assure that the connections do not degrade with repeated temperature cycles.

• Strip the wire(s) so that they fit into the lug with just a bit showing out the other (screw or push-on) end. Too long and your risk interference with the terminals and/or shorting to other terminals. Too short and it is possible that one or more wires will not be properly positioned, will not be properly crimped, and may pull out or make a poor connection. The insulation of the wires should be within the insulating sleeve - there should be no bare wire showing behind the lug.

• Crimp securely but don't use so much force that the insulating sleeve or metal sleeve is severed. Usually 1 or 2 crimps for the actual wire connection and 1 crimp to compress the insulating sleeve will be needed.

• Test the crimp when complete - there should be no detectable movement of the wires. If there is, you didn't crimp hard enough or the lug is too large for your wires.

Wire stripping

A pen knife or Xacto knife can be used in a pinch but a wire stripper is really much much easier.

Attaching wires to screw terminals

1. The best mechanical arrangement is to put the wire under a machine screw or nut, lock washer, and flat washer. However, you will often see just the screw or nut (as in a lamp switch or wall socket). For most applications, this is satisfactory.

2. Avoid the temptation to put multiple wires around a single terminal unless you separate each one with a flat washer.

3. Strip enough of the wire to allow the bare wire to be wrapped once around the terminal. To much and some will poke out and might short to something; too little and a firm mechanical joint and electrical connection may be impossible.

4. For multistranded wire, tightly twist the strands of stripped wire together in a clockwise direction as viewed from the wire end.

5. Wrap the stripped end of the wire **clockwise** around the terminal post (screw or stud) so that it will be fully covered by the screw head, nut, or flat washer. This will insure that the wire is grabbed as the screw or nut is tightened. A pair of small needlenose pliers may help.

6. Hold onto the wire to keep it from being sucked in as the screw or nut is tightened. Don't overdo it - you don't need to sheer off the head of the screw to make a secure reliable connection.

7. Inspect the terminal connection: the bare wire should be fully covered by the head of the screw, nut, or flat washer. Gently tug on the wire to confirm that it is securely fastened.

Test equipment

First, start with some analytical thinking. Many problems associated with household appliances do not require a schematic. Since the internal wiring of many appliances is so simple, you will be able to create your own by tracing the circuits in any case. However, for more complex appliances, a schematic may be useful as wires may run behind and under other parts and the operation of some custom switches may not obvious. The causes for the majority of problems will be self evident once you gain access to the interior - loose connections or broken wires, bad switches, open heating element, worn motor brushes, dry bearings. All you will need are some basic hand tools, a circuit and continuity tester, light oil and grease, and your powers of observation (and a little experience). Your built in senses and that stuff between your ears represents the most important test equipment you have.

The following will be highly desirable for all but the most obvious problems:

1. Circuit tester (neon light) - This is used to test for AC power or confirm that it is off. For safety, nothing can beat the simplicity of a neon tester. Its use is foolproof as there are no mode settings or range selections to contend with. Touch its two probes to a circuit and if it lights, there is power. (This can also take the place of an Outlet tester but it is not as convenient (see below). Cost: $2-$3.

2. Outlet tester (grounds and miswiring) - This will confirm that a 3 prong outlet is correctly wired with respect to Hot, Neutral, and Ground. While not 100% assured of correct wiring if the test passes, the screwup would need to be quite spectacular. This simple device instantly finds missing Grounds and interchanged Hot and Neutral - the most common wiring mistakes. Just plug it into an outlet and if the proper two neon light are lit at full brightness, the outlet is most likely wired correctly. Cost: about $6.

   These are just a set of 3 neon bulbs+resistors across each pair of wires. If the correct bulbs light at full brightness - H-N, H-G - then the circuit is likely wired correctly. If the H-G light is dim or out or if both the H-G and G-N are dim, then you have no ground. If the N-G light is on and the H-G light is off, you have reversed H and N, etc.

   What it won't catch: Reversed N and G (unlikely unless someone really screwed up) and marginal connections since the neon bulbs doesn't use much current. For this (particularly important for the G since it won't do any good if its resistance back to the service panel is too high) you need a real load like a 100 W light bulb. Or, build a tester consisting of 100 W light bulbs (instead of neon lamps) wired between each of the prongs.

   It also won't distinguish between 110 VAC and 220 VAC circuits except that the neon bulbs will glow much brighter on 220 VAC but without a direct comparison, this could be missed.

   For something that appears to test for everything but next week's weather:

   (From: Bill Harnell (bharne@adss.on.ca).)

   Get an ECOS 7105 tester! (ECOS Electronics Corporation, Oak Park, Illinois, 708-383-2505). Not cheap, however. It sold for $59.95 in 1985 when I purchased somewhere around 600 of them for use by our Customer Engineers for safety purposes!

   It tests for:

   Correct wiring, reversed polarity, open Ground, open Neutral, open Hot, Hot & Ground reversed, Hot on neutral, Hot unwired, other errors, over voltage (130 VAC+), under voltage (105 VAC-), Neutral to Ground short, Neutral to Ground reversal, Ground impedance test (2 Ohms or less ground impedance - in the equipment ground conductor).

   Their less expensive 7106 tester performs almost all of the above tests.

   FWIW, I have no interest in the ECOS Corporation of any kind. Am just a very happy customer.

3. Continuity tester (buzzer or light) - Since most problems with appliances boil down to broken connections, open heating elements, defective switches, shorted wires, and bad motor windings, a continuity tester is all that is needed for most troubleshooting. A simple battery operated buzzer or light bulb quickly identifies problems. If a connection is complete, the buzzer will sound or the light will come on. Note that a dedicated continuity tester is preferred over a similar mode on a multimeter because it will operate only at very low resistance. The buzzer on a multimeter sounds whenever the resistance is less than about 200 ohms - a virtual open circuit for much appliance wiring.

   A continuity tester can be constructed very easily from an Alkaline battery, light bulb or buzzer, some wire, and a set of test leads with probes. All of these parts are available at Radio Shack.

                        AA, C, or D cell    1.5 V flashlight bulb or buzzer
                               +|  -             +------------------+
      Test probe 1  o-----------| |--------------|  Bulb or buzzer  |-------+ 
                                |                +------------------+       |
                                                                            |
      Test probe 2  o-------------------------------------------------------+
   

   CAUTION: Do not use this simple continuity tester on electronic equipment as there is a slight possibility that the current provided by the battery will be too high and cause damage. It is fine for most appliances.

4. GFCI tester - outlets installed in potentially wet or outdoor areas should be protected by a Ground Fault Circuit Interrupter (GFCI). A GFCI is now required by the NEC (Code) in most such areas. This tester will confirm that any outlets protected by a GFCI actually will trip the device if there is a fault. It is useful for checking the GFCI (though the test button should do an adequate job of this on its own) as well as identifying or testing any outlets downstream of the GFCI for protection.

   Wire a 3 prong plug with a 15 K ohm 1 W resistor between H and G. Insulate and label it! This should trip a GFCI protected outlet as soon as it is plugged in since it will produce a fault current of about 7 mA.

   Note that this device will only work if there is an actual Safety Ground connection to the outlet being tested. A GFCI retrofitted into a 2 wire installation without a Ground cannot be tested in this way since a GFCI does not create a Ground. However, jumpering this rig between the H and and a suitable earth ground (e.g., a cold water in an all copper plumbing system) should trip the GFCI. Therefore, first use an Outlet Tester (above) to confirm that there is a Safety Ground present.

   The test button works because it passes an additional current through the sense coil between Hot and Neutral tapped off the wiring at the line side of the GFCI and therefore doesn't depend on having a Ground.

   If you want to be fancier, you can build a combination outlet and GFCI tester. Wire up a neon indicator with current limiting resistor) across each pair of wires. Add a 15K ohm 1 W resistor in series with a pushbutton switch between H and G. If the H-G neon is lit (indicating a proper Ground connection), pressing the button should trip the GFCI.

5. Multimeter (VOM or DMM) - This is necessary for actually measuring voltages and resistances. Almost any type will do - even the $14.95 special from Sears. Accuracy is not critical for household appliance repair but reliability is important - for your safety if no other reason. It doesn't really matter whether it is a Digital MultiMeter (DMM) or analog Volt Ohm Meter (VOM). A DMM may be a little more robust should you accidentally put it on an incorrect scale. However, they both serve the same purpose. A cheap DMM is also not necessarily more accurate than a VOM just because it has digits instead of a meter needle. A good quality well insulated set of test leads and probes is essential. What comes with inexpensive multimeters may be too thin or flimsy. Replacements are available. Cost: $15-$50 for a multimeter that is perfectly adequate for home appliance repair.

   Note: For testing of household electrical wiring, a VOM or DMM can indicate voltage between wires which is actually of no consequence. This is due to the very high input resistance/impedance of the instrument. The voltage would read zero with any sort of load. See the section: Phantom voltage measurements of electrical wiring.

Getting inside consumer electronic equipment

Appliance manufacturers seem to take great pride in being very mysterious as to how to open their equipment. Not always, but this is too common to just be a coincidence.

A variety of techniques are used to secure the covers on consumer electronic equipment:

1. Screws: Yes, many still use this somewhat antiquated technique. Sometimes, there are even embossed arrows on the case indicating which screws need to be removed to get at the guts. In addition to obvious screw holes, there may be some that are only accessible when a battery compartment is opened or a trim panel is popped off.

   These are almost always of the Philips variety though more and more appliances are using Torx or security Torx type screws. Many of these are hybrid types - a slotted screwdriver may also work but the Philips or Torx is a whole lot more convenient.

   A precision jeweler's screwdriver set including miniature Philips head drivers is a must for repair of miniature portable devices.

2. Hidden screws: These will require prying up a plug or peeling off a decorative decal. It will be obvious that you were tinkering - it is virtually impossible to put a decal back in an undetectable way. Sometimes the rubber feet can be pryed out revealing screw holes. For a stick-on label, rubbing your finger over it may permit you to locate a hidden screw hole. Just puncture the label to access the screw as this may be less messy then attempting to peel it off.

3. Snaps: Look around the seam between the two halves. You may (if you are lucky) see points at which gently (or forcibly) pressing with a screwdriver will unlock the covers. Sometimes, just going around the seam with a butter knife will pop the cover at one location which will then reveal the locations of the other snaps.

4. Glue: Or more likely, the plastic is fused together. This is particularly common with AC adapters (wall warts). In this case, I usually carefully go around the seam with a hacksaw blade taking extreme care not to go through and damage internal components. Reassemble with plastic electrical tape.

5. It isn't designed for repair. Don't laugh. I feel we will see more and more of this in our disposable society. Some devices are totally potted in Epoxy and are 'throwaways'. With others, the only way to open them non-destructively is from the inside.

When reinstalling the screws, first turn them in a counter-clockwise direction with very slight pressure. You will feel them "click" as they fall into the already formed threads. Gently turn clockwise and see if they turn easily. If they do not, you haven't hit the previously formed threads - try again. Then just run them in as you normally would. You can always tell when you have them into the formed threads because they turn very easily for nearly the entire depth. Otherwise, you will create new threads which will quickly chew up the soft plastic. Note: these are often high pitch screws - one turn is more than one thread - and the threads are not all equal.

The most annoying (to be polite) situation is when after removing the 18 screws holding the case together (losing 3 of them entirely and mangling the heads on 2 others), removing three subassemblies, and two other circuit boards, you find that the adjustment you wanted was accessible through a hole in the case just by partially peeling back a rubber hand grip! (It has happened to me).

When reassembling the equipment make sure to route cables and other wiring such that they will not get pinched or snagged and possibly broken or have their insulation nicked or pierced and that they will not get caught in moving parts. This is particularly critical for AC line operated appliances and those with motors to minimize fire and shock hazard and future damage to the device itself. Replace any cable ties that were cut or removed during disassembly and add additional ones of your own if needed. Some electrical tape may sometimes come in handy to provide insulation insurance as well. As long as it does not get in the way, additional layers of tape will not hurt and can provide some added insurance against future problems. I often put a layer of electrical tape around connections joined with WireNuts(tm) as well just to be sure that they will not come off or that any exposed wire will not short to anything.

Getting built up dust and dirt out of a equipment

Appliances containing fans or blowers seem to be dust magnets - an incredible amount of disgusting fluffy stuff can build up in a short time - even with built-in filters.

Use a soft brush (like a new cheap paint brush) to remove as much dirt, dust, and crud, as possible without disturbing anything excessively. Some gentle blowing (but no high pressure air) may be helpful in dislodged hard to get at dirt - but wear a dust mask.

Don't use compressed air on intricate mechanisms, however, as it might dislodge dirt and dust which may then settle on lubricated parts and contaminating them. High pressure air could move oil or grease from where it is to where it should not be. If you are talking about a shop air line, the pressure may be much much too high and there may be contaminants as well.

A Q-tip (cotton swab) moistened with politically correct alcohol can be used to remove dust and dirt from various hard to get at surfaces.

Lubrication of appliances and electronic equipment

NEVER, ever, use WD40! WD40 is not a good lubricant despite the claims on the label. Legend has it that the WD stands for Water Displacer - which is one of the functions of WD40 when used to coat tools for rust prevention. WD40 is much too thin to do any good as a general lubricant and will quickly collect dirt and dry up. It is also quite flammable and a pretty good solvent - there is no telling what will be affected by this.

A light machine oil like electric motor or sewing machine oil should be used for gear or wheel shafts. A plastic safe grease like silicone grease or Molylube is suitable for gears, cams, or mechanical (piano key) type mode selectors. Never use oil or grease on electrical contacts.

One should also NOT use a detergent oil. This includes most automotive engine oils which also have multiple additives which are not needed and are undesirable for non-internal combustion engine applications.

3-In-One(tm) isn't too bad if that is all you have on hand and the future of the universe depends on your fan running smoothly. However, for things that don't get a lot of use, it may gum up over time. I don't know whether it actually decomposes or just the lighter fractions (of the 3) evaporate.

Unless the unit was not properly lubricated at the factory (which is quite possible), don't add any unless your inspection reveals the specific need. Sometimes you will find a dry bearing, motor, lever, or gear shaft. If possible, disassemble and clean out the old lubricant before adding fresh oil or grease.

Note that in most cases, oil is for plain bearings (not ball or roller) and pivots while grease is used on sliding parts and gear teeth.

In general, do not lubricate anything unless you know there is a need. Never 'shotgun' a problem by lubricating everything in sight! You might as well literally use a shotgun on the equipment!

Common appliance problems

1. Broken wiring inside cordset - internal breaks in the conductors of cordsets or other connecting cords caused by flexing, pulling, or other long term abuse. This is one of the most common problem with vacuum cleaners which tend to be dragged around by their tails.

   Testing: If the problem is intermittent, (or even if it is not), plug the appliance in and turn it on. Then try bending or pushing the wire toward the plug or appliance connector end to see if you can make the internal conductors touch at least momentarily. Ii the cordset is removable, test between ends with a continuity checker or multimeter on the low ohms scale. If it is not detachable, open the appliance to perform this test.

2. Bad internal connections - broken wires, corroded or loosened terminals. Wires may break from vibration, corrosion, poor manufacturing, as well as thermal fatigue. The break may be in a heating element or other subassembly. In many cases, failure will be total as in when one of the AC line connections falls off. At other times, operation will be intermittent or erratic - or parts of the appliance will not function. For example, with a blow dryer, the heating element could open up but the fan may continue to run properly.

   Testing: In many cases, a visual inspection with some careful flexing and prodding will reveal the location of the bad connection. If it is an intermittent, this may need to be done with a well insulated stick while the appliance is on and running (or attempting to run). When all else fails, the use of a continuity checker or multimeter on the low ohms scale can identify broken connections which are not obviously wires visibly broken in two. For testing heating elements, use the multimeter as a continuity checker may not be sensitive enough since the element normally has some resistance.

3. Short circuits. While much less frequent than broken or intermittent connections, two wires touching or contacting the metal case of an appliance happens all too often. Partially, this is due to the shoddy manufacturing quality of many small appliances like toaster ovens. These also have metal (mostly) cabinets and many metal interior parts with sharp edges which can readily eat through wire insulation due to repeated vibrations, heating and cooling cycles, and the like. Many appliances are apparently designed by engineers (this is being generous) who do not have any idea of how to build or repair them. Thus, final assembly, for example, must sometimes be done blind - the wires get stuffed in and covers fastened - which may end up nicking or pinching wires between sharp metal parts. The appliance passes the final inspection and tests but fails down the road.

   A short circuit may develop with no operational problems - but the case of the appliance will be electrically 'hot'. This is a dangerous situation. Large appliances with 3 wire plugs - plugged into a properly grounded 3 wire circuit - would then blow a fuse or trip a circuit breaker. However, small appliances like toaster, broilers, irons, etc., have two wire plugs and will just set there with a live cabinet.

   Testing: Visually inspect for bare wires or wires with frayed or worn insulation touching metal parts, terminals they should not be connected to, or other wires. Use a multimeter on the high ohms scale to check between both prongs of the AC plug and any exposed metal parts. Try all positions of any power or selector switches. Any resistance measurement less than 100K ohms or so is cause for concern - and further checking. Also test between internal terminals and wires that should not be connected together.

   Too many people like to blame everything from blown light bulbs to strange noises on short circuits. A 'slight', slow, or marginal short circuit is extremely rare. Most short circuits in electrical wiring between live and neutral or ground (as opposed to inside appliances where other paths are possible) will blow a fuse or trip a breaker. Bad connections (grounds, neutral, live), on the other hand, are much much more common.

4. Worn, dirty, or broken switches or thermostat contacts. These will result in erratic or no action when the switch is flipped or thermostat knob is turned. In many cases, the part will feel bad - it won't have that 'click' it had when new or may be hard to turn or flip. Often, however, operation will just be erratic - jiggling the switch or knob will make the motor or light go on or off, for example.

   Testing: Where there is a changed feel to the switch or thermostat with an associated operational problem, there is little doubt that the part is bad and must be replaced. Where this is not the case, label the connections to the switch or thermostat and then remove the wires. Use the continuity checker or ohmmeter across each set of contacts. They should be 0 ohms or open depending on the position of the switch or knob and nothing in between. In most cases, you should be able to obtain both readings. The exception is with respect to thermostats where room temperature is off one end of their range. Inability to make the contacts open or close (except as noted above) or erratic intermediate resistances which are affected by tapping or jiggling are a sure sign of a bad set of contacts.

5. Gummed up lubrication, or worn or dry bearings. Most modern appliances with motors are supposedly lubricated for life. Don't believe it! Often, due to environmental conditions (dust, dirt, humidity) or just poor quality control during manufacture (they forgot the oil), a motor or fan bearing will gum up or become dry resulting in sluggish and/or noisy operation and overheating. In extreme cases, the bearing may seize resulting in a totally stopped motor. If not detected, this may result in a blown fuse (at the least) and possibly a burnt out motor from the overheating.

   Testing: If the appliance does not run but there is a hum (AC line operated appliances) or runs sluggishly or with less power than you recall when new, lubrication problems are likely. With the appliance unplugged, check for free rotation of the motor(s). In general, the shaft sticking out of the motor itself should turn freely with very little resistance. If it is difficult to turn, the motor bearings themselves may need attention or the mechanism attached to the motor may be filled with crud. In most cases, a thorough cleaning to remove all the old dried up and contaminated oil or grease followed by relubing with similar oil or grease as appropriate will return the appliance to good health. Don't skimp on the disassembly - total cleaning will be best. Even the motor should be carefully removed and broken down to its component parts - end plates, rotor, stator, brushes (if any) in order to properly clean and lubricate its bearings. See the appropriate section of the chapter: Motors 101 for the motor type in your appliance.

6. Broken or worn drive belts or gears - rotating parts do not rotate or turn slowly or with little power even through the motor is revving its little head off. When the brush drive belt in an upright vacuum cleaner breaks, the results are obvious and the broken belt often falls to the ground (to be eaten by the dog or mistaken for a mouse tail - Eeek!) However, there are often other belts inside appliances which will result in less obvious consequences when they loosen with age or fail completely.

   Testing: Except for the case of a vacuum cleaner where the belt is readily accessible, open the appliance (unplugged!). A good rubber belt will be perfectly elastic and will return to its relaxed length instantly when stretched by 25 percent and let go. It will not be cracked, shiny, hard, or brittle. A V-type belt should be dry (no oil coating), undamaged (not cracked, brittle, or frayed), and tight (it should deflect 1/4" to 1/2" when pressed firmly halfway between the pulleys).

   Sometimes all that is needed is a thorough cleaning with soap and water to remove accumulated oil or grease. However, replacement will be required for most of these symptoms. Belts are readily available and an exact match is rarely essential.

7. Broken parts - plastic or metal castings, linkages, washers, and other 'doodads' are often not constructed quite the way they used to be. When any of these fail, they can bring a complicated appliance to its knees. Failure may be caused by normal wear and tear, improper use (you tried to vacuum nuts and bolts just like on TV), accidents (why was your 3 year old using the toaster oven as a step stool?), or shoddy manufacturing.

   Testing: In many cases, the problem will be obvious. Where it is not, some careful detective work - putting the various mechanisms through their paces - should reveal what is not functioning. Although replacement parts may be available, you can be sure that their cost will be excessive and improvisation may ultimately be the best approach to repair. See the section: Fil's tips on improvised parts repair.

8. Insect damage. Many appliance make inviting homes for all sort of multi- legged creatures. Evidence of their visits or extended stays will be obvious including frayed insulation, short circuits caused by bodily fluids or entire bodies, remains of food and droppings. Even the smallest ventilation hole can be a front door.

   The result may be any of the items listed in (1) to (7) above. Once the actual contamination has been removed and the area cleaned thoroughly, inspect for damage and repair as needed. If the appliance failed while powered, you may also have damage to wiring or electronic components due to any short circuits that were created by the intruders' activities.

Types of Parts Found in Small Appliances

So many, so few

The following types of parts are found in line powered appliances:

• Cordsets - wire and plug.
• Internal wiring - cables and connectors.
• Switches - power, mode, or speed selection.
• Relays - electrically activated switches for power or control.
• Electrical overload protection devices - fuses and circuit breakers.
• Thermal protection devices - thermal fuses and thermal switches.
• Controls 1 - adjustable thermostats and humidistats.
• Controls 2 - rheostats and potentiometers.
• Interlocks - prevent operation with case or door open.
• Light bulbs - incandescent and fluorescent.
• Indicators - incandescent or neon light bulbs or LEDs.
• Heating elements - NiChrome coils or ribbon, Calrod, Quartz.
• Solenoids - small and large.
• Small electronic components - resistors, capacitors, diodes.
• Transformers - low voltage, high voltage.
• Motors - universal, induction, DC, timing.
• Fans and Blowers - bladed or centrifugal.
• Bearings and bushings.
• Mechanical controllers - timing motors and cam switches.
• Electronic controllers - simple delay or microprocessor based.

• Batteries - Alkaline, Lithium, Nickel-Cadmium, Lead-acid.
• AC adapters and chargers - wall 'warts' with AC or DC outputs.

Cordsets - wire and plug

CAUTION: Some cordsets are more than what meets the eye. See the section: When a cordset is more than a cord and plug.

Most plug-in appliances in the U.S. will have one of 3 types of line cord/plug combinations:

1. Non-polarized 2 prong: The 2 prongs are of equal width so the plug may be inserted in either direction. These are almost universal on older appliances but may be found on modern appliances as well which are double insulated or where polarity does not matter. (Note: it **must** not matter for user safety in any case. The only time it can matter otherwise is with respect to (1) possible RFI (Radio Frequency Interference) generation or (2) service safety (this would put the center contact of a light bulb socket or internal switch and fuse on the Hot wire).

2. Polarized 2 prong: The prong that is supposed to be plugged into the Neutral slot of the outlet is wider. All outlets since sometime around the 1950s (???) have been constructed to accept polarized plugs only one way. While no appliance should ever be designed where the way it is plugged in can result in a user safety hazard, a lamp socket where the shell - the screw thread part - is plugged into Neutral is less hazardous when changing a light bulb. In addition, when servicing a small appliance with the cover removed, the Hot wire with a polarized plug should go to the switch and fuse and thus most of the circuitry will be disconnected with the switch off or fuse pulled.

   Thus, if you are replacing a plug and don't know (or didn't label) how the old one was hooked up, the narrow prong should go to the fuse, switch, thermostat or other control, center of the socket, etc. Since you may have trouble finding non-polarized plugs these days, this applies to older appliances as well and there is really no problem in replacing a non-polarized plug with a polarized one on an appliance.

3. Grounded 3 prong: In addition to Hot and Neutral, a third grounding prong is provided to connect the case of the equipment to safety Ground. This provides added protection should internal wiring accidentally short to a user accessible metal cabinet or control. In this situation, the short circuit will (or is supposed to) blow a fuse or trip a circuit breaker or GFCI rather than present a shock hazard. DO NOT just cut off the third prong if your outlet does not have a hole for it. Have the outlet replaced with a properly grounded one (which may require pulling a new wire from the service panel). As a short term solution, the use of a '3 to 2' prong adapter is acceptable IF AND ONLY IF the outlet box is securely connected to safety Ground already (BX or Romex cable with ground). Grounding also is essential for surge suppressors to operate properly (to the extent that they ever do) and may reduce RFI susceptibility and emissions if line filters are included (as with computer equipment and consumer electronics). Power conditioners require the Ground connection for line filtering as well.

Light duty cordsets are acceptable for most appliances without high power heating elements or heavy duty electric motors. These include table lamps, TVs, VCRs, stereo components, computers, dot matrix and inkjet printers, thermal fax machines, monitors, fans, can openers, etc. Electric blankets, heating pads, electric brooms, and food mixers are also low power and light duty cordsets are acceptable. The internal wires used is #18 AWG which is the minimum acceptable wire size (highest AWG number) for any AC line powered device.

Medium or heavy duty cordsets are REQUIRED for heating appliances like electric heaters (both radiant and convection), toasters, broilers, steam and dry irons, coffee makers and electric kettles, microwave and convection ovens, laser printers, photocopiers, Xerographic based fax machines, canister and upright vacuum cleaners and shop vacs, floor polishers, many portable and most stationary power tools. The internal wires used will be #16 AWG (medium duty) or #14 AWG (heavy duty).

For replacement, always check the nameplate amps or wattage rating and use a cordset which has a capacity at least equal to this. The use of an inadequate cordset represents a serious fire hazard.

Three prong grounded cordsets are required for most computer equipment, heavy appliances, and anything which is not double insulated and has metal parts that may be touched in normal operation (i.e., without disassembly).

The individual wires in all cordsets except for unpolarized types (e.g., older lamp cord) will be identified in some way. For sheathed cables, color coding is used. Generally, in keeping with the NEC (Code), black will be Hot, white will be Neutral, and green will be Safety Ground. You may also find brown for Hot, blue for Neutral, and green with a yellow stripe for Safety Ground. This is used internationally and is quite common for the cordsets of appliances and electronic equipment.

For zip cord with a polarized plug, one of the wires will be tagged with with a colored thread or a ridge on the outer insulation to indicate that it is the Neutral wire. For unpolarized types, no identification is needed (though there still may be some) as the wires and prongs of the plug are identical. However, fewer and fewer devices use non-polarized cords/plugs now so you are more likely to see this with older ones.

In general, when replacement is needed, use the same configuration and length and a heavy duty type if the original was heavy duty.

• Substituting a heavy duty cordset for a light duty one is acceptable as long as the additional stiffness is acceptable in terms of convenience.

• A shorter cord can usually be used if desired. In most cases, a longer cord (within reason) can be substituted as well. However, performance of heavy duty high current high wattage appliances may suffer if a really long cord (or extension cord) is used voltage drop from the wire resistance. For a modest increase in length, use the next larger wire size (heavy duty instead of medium duty, #14 instead of #16, for example).

• Where the old one was non-polarized, a polarized replacement is fine and usually preferred, for example, if:
  • It is an incandescent fixture. Connect the Neutral (wide prong/ridged wire) to the shells of the light bulb sockets.

  • It has an on/off switch or fuse in-line with the power. Connect the Hot wire to that side of the input.

  • There is a high value resistor and/or capacitor network between one side of the line and the case (for RFI suppression). Connect this to the Neutral.

  If the input is completely symmetric (e.g., it goes into a power transformer and no where else), then the polarity doesn't matter.

Before disconnecting the old cord, label connections or make a diagram and then match the color code or other wire identifying information. In all cases, it is best to confirm your final wiring with a continuity tester or multimeter on the low ohms scale. Mistakes on your part or the manufacturer of the new cord are not unheard of!

Common problems: internal wiring conductors broken at flex points (appliance or plug). With yard tools, cutting the entire cord is common. The connections at the plug may corrode as well resulting in heating or a broken connection.

Testing: Appliance cordsets can always be tested with a continuity checker or multimeter on a the low ohms scale.

Squeeze, press, spindle, fold, mutilate the cord particularly at both ends as while testing to locate intermittent problems.

If you are too lazy to open the appliance (or this requires the removal of 29 screws), an induction type of tester such as used to locate breaks in Christmas tree light strings can be used to confirm continuity by plugging the cord in both ways and checked along its length to see if a point of discontinuity can be located. A permanent bench setup with a pair of outlets (one wired with reverse polarity and clearly marked: FOR TESTING ONLY) can be provided to facilitate connecting to either of the wires of the cordset when using an induction type tester.

Note: broken wires inside the cordset at either the plug or appliance end are among the most common causes of a dead vacuum cleaner due to abuse it gets - being tugged from the outlet, vacuum being dragged around by the cord, etc. Many other types of appliances suffer the same fate. Therefore, checking the cord and plug should be the first step in troubleshooting any dead appliance.

If the cord is broken at the plug end, the easiest thing to do is to replace just the plug. A wide variety of replacement plugs are available of three basic types: clamp-on/insulation piercing, screw terminals, and wire compression.

• Clamp-on/insulation piercing plugs are installed as follows: First, the cord is cleanly cut but not stripped and inserted into the body of the plug. A lid or clamping bar is then closed which internally pierces the insulation and makes contact with the prongs. When used with the proper size wire, these are fairly reliable for light duty use - table lamps and other low power appliances. However, they can lead to problems of intermittent or bad connections if the wire insulation thickness does not precisely match what the plug expects.

• Plugs with screw terminals make a much more secure robust connections but require a bit more time and care in assembly to assure a proper connection and avoid stray wire strands causing short circuits or sticking out and representing a shock hazard. Tightly twist the strands of the stripped wire together before wrapping around the screw in a clockwise direction before tightening. Don't forget to install the fiber insulator that is usually supplied with the plug.

• The best plugs have wire clamp terminals. The stripped end of the wire is inserted into a hole and a screw is tightened to clamp the wire in place. Usually, a molded plastic cover is then screwed over this assembly and includes a strain relief as well. These are nearly foolproof and consequently are used in the most demanding industrial and medical applications. They are, not surprisingly, also typically the most expensive.

When a cordset is more than a cord and plug

• Sometimes, the plugs themselves include built-in fuses which if blown, might result in an incorrect diagnosis of a bad cordset. And, replacing the cordset with a normal one would result in the loss of the prtection provided by the fuses.

• A variety of electronic equipment as well as rechargeable (and other) appliances now use switching power supply type wall adapters rather than the usual bulky, heavy wall transformer. These weigh almost nothing and are only slighly larger than a normal wall plug. However, they are an essential part of the unit since the AC line voltage is converted into a lower DC voltage inside the oversize plug! These are functionally equivalent to the more common type (probably better in fact in terms of regulation and efficiency) and both provide the essential line isolation required for safety. Neither the entire cordset nor the plug can be cut off and replaced. An exact replacement for that particular model must be installed.

• Some appliances include either a Ground Fault Circuit Interrupter (GFCI) or what I call a GFCK (Ground Fault Circuit Killer) in an oversize plug. These provide protection from shock for items like hair dryers that might contact or be dropped into water. A GFCI can be reset once the fault condition is removed (it is unplugged and dried out). A GFCK is a one time circuit breaker type device. If it is activated, the appliance will need to be repaired to reset it (which may not be worth the cost since it will require replacement of the special GFCK cordset). While the appliance will still work if the special plug or the entire cordset is replaced with a normal one, the protection will be lost and it should then ONLY be used in a GFCI protected outlet. See the sections: "What is a GFCI?" and "The Ground Fault Circuit Killer (GFCK)".

Appliance cord gets hot

Of course, if the problem is with an *extension* cord, then either it is overloaded or defective. In either case, the solution should be obvious.

Some cords will run warm just by design (or cheapness in design using undersized conductors).

However, if it is gets hot during use, this is a potential fire hazard.

If it is hot mainly at the plug end - get a heavy duty replacement plug - one designed for high current appliances using screw terminals - at a hardware store, home center, or electrical supply house. Cut the cord back a couple of inches.

If the entire cord gets warm, this is not unusual with a heater. If it gets really hot, the entire cord should be replaced. Sometimes with really old appliance, the copper wires in the cord oxidize even through the rubber insulation reducing their cross section and increasing resistance. This leads to excessive power dissipation in the cord. Replacement *heavy duty* cordsets are readily available.

Note that just because the cord itself gets warm does NOT mean that the wiring in the walls is heating significantly. The smallest allowable wiring size inside the walls is #14 which has a resistance of about 2.5 ohms per thousand feet. An appliance drawing 10 A through 50 feet of cable (100 total feet of wire going both ways) would result in a 2.5 V drop and 25 W dissipation. But since this is distributed over 50 feet of cable, heating in any location is minimal.

Extension cords

Extension cord rules of use:

• The capacity must be at least equal to the SUM of the wattages or amperages of all the appliances plugged in at the far end. Larger is fine as well and is desirable for long extensions. Check the rating marked on the cord or a label attached to the cord. Thickness of the outside of the cord is not a reliable indication of power rating.

• Use a type which is the most restrictive of any appliances that will be plugged in (e.g., 3 prong if any are of this type, 2 prong polarized otherwise unless your outlets are non-polarized (old dwellings).

• Use only outdoor type extension cords (usually colored ye