Notes on the Troubleshooting and Repair of Audio Equipment and Other Miscellaneous Stuff


[Document Version: 2.86] [Last Updated: 05/25/1998]

Chapter 1) About the Author & Copyright

Notes on the Troubleshooting and Repair of Audio Equipment and Other Miscellaneous Stuff

Author: Samuel M. Goldwasser
Corrections/suggestions: | Email

Copyright (c) 1994, 1995, 1996, 1997, 1998
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.

Chapter 2) Introduction

  2.1) Why is all that junk in your attic?

If you have ever tried to get a piece of consumer electronic equipment
repaired, you understand why so much dead stuff is likely to be gathering
dust in your attic or basement closet or junk box.  It does not pay!  This
may be partially by design.  However, to be fair, it may take just as much
time to diagnose and repair a problem with a $20 Walkman as a $300 VCR and
time is money for a repair shop.  It is often not even economical to repair
the more expensive equipment let alone a $40 answering machine.  The cost
of the estimate alone would probably buy at least one new unit and possibly
many more.

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 boombox to take take to
the beach may just make sense after all.

This document provides maintenance and repair information for a variety
of consumer electronic devices not covered 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.  As most difficulties encountered with this type of equipment are
mechanical, there is significant emphasis on dirt, lubrication, deteriorated
rubber parts, broken doohickies, and so forth.  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 - or decide that replacement
is indeed the better option.  However, in many cases, you will be able to do
what is required to repair a piece of equipment for a fraction of what would
be charged by a repair center.  Perhaps, you will even 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)!

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.  It will also be easier to do
further research using a repair book or guide.  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 new-found knowledge, you will have the upper hand and will not
easily be snowed by a dishonest or incompetent technician.

If you are just getting started, you should refer to "Repair Briefs, an
Introduction" for additional troubleshooting tips, recommended test
equipment, suggested parts inventory, and other general information.

  2.2) Information on consumer electronics technology

Your local public library (621.384 if your library is numbered that way)
or technical bookstore represents a valuable resource for books on both
the technology and repair of a large variety of consumer electronics

For general troubleshooting techniques, see the section: "Some general references".

  2.3) Web sites dealing with low voltage wiring

These sites deal with non-power wiring information: phones, audio, video,
home automation, etc.  Since much of the content of this document relates
to home electronics that may involve such wiring, these sites may be of
interest.  The first also has a pile of links to other related sites.

* http://www.mcdata.com/~meh0045/homewire/wire_guide.html
* http://www.geocities.com/SiliconValley/Pines/4116/
* http://www.geocities.com/ResearchTriangle/3300/
* http://us016757.home.mindspring.com  (Engineering Notebook section)

Chapter 3) Maintenance and Troubleshooting Guide

  3.1) SAFETY

The only danger to you in most of these devices is the AC line connection
(if any) and getting sucked into any mechanical people traps.  Before you
plug in the unit with any covers removed, make note and cover up any
exposed AC line connections.  The rest of the circuitry is low voltage
and while you can destroy your equipment by your actions, you should be
fairly safe.  Exceptions to this are noted where appropriate.

However, you never can tell where an exciting troubleshooting
expedition will lead.  The following Safety Guidelines are included
for your survival when working on line connected or high voltage
equipment (and your reading enjoyment).

  3.2) Safety guidelines

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.

The purpose of this set of guidelines is not to frighten you but rather to
make you aware of the appropriate precautions.  Repair of TVs, monitors,
microwave ovens, and other consumer and industrial equipment can be both
rewarding and economical.  Just be sure that it is also safe!

* 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

* Know your equipment: TVs and monitors may use parts of the metal chassis
  as ground return yet the chassis may be electrically live with respect to the
  earth ground of the AC line.  Microwave ovens use the chassis as ground
  return for the high voltage.  In addition, do not assume that the chassis
  is a suitable ground for your test equipment!

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

* 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 20K-100K ohm resistor).  Monitor while discharging and/or verify that
  there is no residual charge with a suitable voltmeter.

* For TVs and monitors in particular, there is the additional danger of
  CRT implosion - take care not to bang the CRT envelope with your tools.
  An implosion will scatter shards of glass at high velocity in every
  direction.  There is several tons of force attempting to crush the typical
  CRT.  Always wear eye protection.

* 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.

* 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.

* Perform as many tests as possible with power off and the equipment unplugged.
  For example, the semiconductors in the power supply section of a TV or
  monitor can be tested for short circuits with an ohmmeter.

* 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 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.  A circuit breaker is too slow and insensitive to provide any
  protection for you or in many cases, your equipment.  The GFCI may protect
  your scope probe from smoking if you accidentally connect its ground 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!

  3.3) Troubleshooting tips

Many problems have simple solutions.  Don't immediately assume that
your problem is some combination of esoteric complex convoluted
failures.  For a tape deck, it may just be a bad belt or a bad tape.
Try to remember that the problems with the most catastrophic impact on
operation (a dead AC adapter) have the simplest solutions (repair the
wires broken due to flexing in the power cable).

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).

Whenever working on precision equipment, make copious notes and diagrams.
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 for storage.

Another consideration is ESD - Electro-Static Discharge.  The electronic
components in a some devices like cassette decks, Walkmen, and portable
phones, are vulnerable to ESD.  There is no need to go overboard but taking
reasonable precautions like not wearing clothing made of wool that tends
to generate static.  When working on larger devices like cassette decks, get
into the habit of touching a ground like the metal chassis before touching
any circuit components.

A basic set of precision hand tools will be all you need to disassemble
and perform adjustments on most consumer electronics equipment.  These
do not need to be really expensive but poor quality tools are worse than
useless and can cause damage.  Needed tools include a selection of Philips
and straight blade screwdrivers, needlenose pliers, wire cutters, tweezers,
and dental picks. A jeweler's screwdriver set is a must particularly if you
are working on compact equipment.  For adjustments, a miniature (1/16" blade)
screwdriver with a non-metallic tip is desirable both to prevent the
presence of metal from altering the electrical properties of the circuit
and to minimize the possibility of shorting something from accidental
contact with the circuitry.

For thermal or warmup problems, a can of 'cold spray' or 'circuit chiller'
(they are the same) and a heat gun or blow dryer come in handy to identify
components whose characteristics may be drifting with temperature.  Using the
extension tube of the spray can or making a cardboard nozzle for the heat
gun can provide very precise control of which components you are affecting.

For info on useful chemicals, adhesives, and lubricants, see "Repair Briefs,
an Introduction" as well as other documents available at this site.

  3.4) Soldering equipment

The ease and quality of your work will depend both on proper soldering as
well as desoldering (often called rework) equipment.

* A low wattage (25 W) iron for delicate components including discrete
  semiconductors, ICs, other small parts).

* A medium wattage (40-50W) iron for heavy duty circuit board work including
  power components, power plane connections, and large transformers).

* A 100-140 W soldering gun for chassis connections.

Three wire grounded soldering equipment is recommended but I do not consider
it essential for this type of repair work.  However, a temperature regulated
soldering station is a really nice piece of equipment if you can afford it or
happen on a really good deal.

I consider fine gauge rosin core solder (.030 or less) to be best for most
applications (e.g., Ersin Multicore).

* Desoldering pump - SoldaPullit or similar 'solder sucker' for removing
  components easily and usually nondestructively.  SolderWick is also
  handy for cleaning up desoldered connections.

A vacuum rework station is not needed unless you are removing your soldered
in 500 pin Intel P6!

  3.5) Soldering techniques

Soldering is a skill that is handy to know for many types of construction
and repair.  For modern small appliances, it is less important than it once
was as solderless connectors have virtually replaced solder for internal

However, there are times where soldering is more convenient.  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.

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

* 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.

Practice on some scrap wire and electronic parts.  It should take you about
3 minutes to master the technique!

  3.6) Desoldering techniques

Occasionally, it will be necessary to remove solder - either excess or
to replace wires or components.  A variety of tools are available for
this purpose.  The one I recommend is a vacuum solder pump called
'SoldaPullet' (about $20).  Cock the pump, heat the joint to be cleared,
and press the trigger.  Molten solder is sucked up into the barrel of the
device leaving the terminal nearly free of solder.  Then use a pair of
needlenose pliers and a dental pick to gently free the wires or component.
Other approaches that may be used in place of or in addition to this:
Solder Wick which is a copper braid that absorbs solder via capillary
action; rubber bulb type solder pumps, and motor driven vacuum solder
rework stations (pricey).

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

  3.7) Soldering pins in plastic connectors

The thermoplastic used to mold many common cheap connectors softens or
melts at relatively low temperatures.  This can result in the pins popping
out or shifting position (even shorting) as you attempt to solder to them
to replace a bad connection, for example.

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.

  3.8) Test equipment

Don't start with the electronic test equipment, start with some analytical
thinking.  Many problems associated with consumer electronic equipment
do not require a schematic (though one may be useful).  The majority
of problems with consumer electronics equipment are mechanical and can be
dealt with using nothing more than a good set of precision hand tools; some
alcohol, degreaser, contact cleaner, 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.

A DMM or VOM is necessary for checking of power supply voltages and
testing of sensors, LEDs, switches, and other small components.  This does
not need to be expensive but since you will be depending on its readings,
reliability is important.  Even a relatively inexpensive DMM from Radio
Shack will be fine for most repair work.  You will wonder how you ever
lived without one!  Cost: $25-50.

Unless you get deep into electronic repair, a high bandwidth oscilloscope
is not required.  However, a relatively inexpensive 5 or 10 MHz dual trace
scope is very handy and you will find all kinds of uses for it.  Such a
scope should cost less than $150 on the used market.

There are several specific pieces of test equipment that you may already own
which are required depending on the devices being fixed.

Audio equipment:

* Stereo tuner or other audio signal source.  An audio signal generator 
  is nice but not really essential.

* An audio amp connected to a loudspeaker.  The input should be selectable
  between line level and mic level and be brought out through a shielded
  cable to a test probe and ground clip.  This is useful for tracing
  an audio circuit to determine where a signal is getting lost.  Inexpensive
  signal tracers are also available but this option is likely free.

* Prerecorded and garbage cassettes or tapes for testing of component
  and walkman tape transports.

Video games, cable boxes, and other video sources:

* A TV (preferably color) with RF (antenna) inputs connected to a VCR
  with a working tuner and RF modulator or a TV with both RF and A/V (RCA
  jacks) inputs.

* A known good game cartridge to confirm that the problem is in the game

Telephone equipment:

* A working tone dialing phone.  If I had a choice, it would be a good
  old reliable ATT Touch Tone desk phone.

* A dual connector phone jack.  Two independent phone lines are desirable
  for answering machine or modem testing.

* A PC or laptop with a fax-modem (for modem and fax machine testing).

* A low voltage DC power supply or wall wart to perform certain tests
  without a telephone connection or phone line simulator.

* A handy-dandy phone line tester.  The inexpensive variety is just a pair of
  LEDs in series with a resistor for each line attached to an RJ11 connector.
  However, this is much more convenient than fumbling with a multimeter!  You
  can buy one at Radio Shack (about $7) or easily build your own.  See the
  section: "Handy-dandy phone line tester" for details.

  3.9) Handy-dandy phone line tester

This simple device (total cost about $3) will show at a glance the status of
all of the phone lines connected to a modular jack.

Parts list: Surface mount RJ11 modular jack, RJ11 extension cord.
            For each phone line: 2 LEDs (red and green), 10K resistor.

Construct the following circuit for each line and attach to the appropriate
color terminals/wires of the modular jack:

                           10K            Green LED
Line 1:     (Green) o------/\/\-----+--------|>|-------+------o (Red
Line 2:     (Black)                 |  Wiring Correct  |        (Yellow)
Line 3:     (White)                 |                  |        (Blue)
                                    |      Red LED     |
                                      Reverse Polarity

Note: Polarity of Tip and Ring are reversed with respect to the wire colors
because of swap that occurs using the RJ11 extension cord.

Mount the LEDs in holes drilled in the plastic cover of the modular jack
(making sure they clear the base when the cover is screwed down).

To test old style 4 prong phone jacks, use an adapter on the end of the RJ11
extension cord.

Correctly wired lines will light up green, reverse polarity will be red, dead
line will be dark, line-in-use will be dark or nearly dark.  If you catch a
line that is ringing. both LEDs will flicker.

Putting just the LED portion (leave out the resistor) of this circuit in
*series* with the phone line will implement an off-hook (in use) indicator.

  3.10) Getting inside consumer electronic equipment

Yes, you will void the warranty, but you knew this already.

Note: the sections on loudspeakers, cameras, and watches have additional
'getting inside' info.

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 or cassette compartment is opened or a trim panel is popped off.

   These will often be of the Philips variety.  (Strictly speaking, many
   of these are not actual Philips head screws but a slight variation.
   Nonetheless, a Philips screwdriver of suitable size will work on them.)
   A precision jeweler's  screwdriver set including miniature Philips
   head drivers is a must for repair of miniature portable devices.

   Sometimes, you will find Torx or a variety of security type fasteners.
   Suitable driver bits are available.  Sometimes, you can improvise
   using regular tools.  In the case of security Torx, the center post can
   usually be broken off with a pair of needlenose pliers allowing a normal
   Torx driver to be used.  In a pinch, a suitable size hex wrench can
   substitute for a Torx driver.   Places like MCM Electronics carry a
   variety of security bits.

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

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.

Don't force anything unless you are sure there is no alternative - most
of the time, once you determine the method of fastening, covers will
come apart easily.  If they get hung up, there may be an undetected
screw or snap still in place.

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!

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.  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.

  3.11) Getting built up dust and dirt out of a equipment

This should be the first step in any inspection and cleaning procedure.

Do not be tempted to use compressed air!

I would quicker use a soft brush to carefully dust off the circuit boards and
power supply.  Work in such a way that the resulting dust does not fall on
the mechanical parts.

For intricate mechanisms, using compressed air could dislodge dirt and dust
which may then settle on lubricated parts 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 surfaces of the deck (in addition to
the normal proper cleaning procedures for the guides, rollers, heads,
wheels, belts, etc.)

  3.12) What to do if a tiny tiny part falls inside

We have all done this: a tiny washer or spring pops off and disappears
from sight inside the guts of the unit.  Don't panic.  First - unplug it
if AC powered.  Remove the battery pack if possible from a portable device.

Try to locate the part with a bright light without moving anything.  You may
have gotten lucky (yeh, right).  Next, over an area where a dropped part
will be visible (not a shag carpet!), try any reasonable means to shake
it loose - upside down, a little gently tapping and shaking, etc.  A hard
surface is better in some ways as you might hear the part drop.  On the
other hand it may bounce into the great beyond.

If this does not work, you have two options:

1. Assume that the part has landed in a place that will not cause future
   problems.  There could be electrical problems if it is metallic and shorts
   out some circuitry or there could be mechanical problems if it jams some
   part of the mechanism.  There is an excellent chance that the part will
   never cause any harm.  What chance?  I don't know, maybe 99%.  It is not
   worth taking the unit to pieces to locate the part.  You are more likely to
   damage something else in the process.  Obtain a replacement and get on
   with your life.  The exception is, of course, if you now begin experiencing
   problems you **know** were not there before.

2. Take the unit to pieces in an attempt to locate the part.  For all you
   know, it may be clear across the room and you will never find it inside.
   If all the gymnastics have not knocked it loose, then it may be really
   wedged somewhere and will stay there - forever.  If the unit behaves
   normally, then in all likelihood it will continue to do so.

To prevent this sort of thing from happening in the future you will no doubt
be much more careful.  Sure you will!  Some suggestions to prevent ejection
of an E-clip, split washer, or spring into the great beyond:

* Construct a paper dam around the area.

* Tie a thread or fine wire around the part before attempting to remove it.
  Keep this 'safety line' on until after it has been reinstalled, then just
  pull it free.

* Keep one finger on the part as you attempt to pop it free.

* Hold onto the part with a pair of needlenose pliers or tweezers while prying
  with a small screwdriver.

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