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


  7.11) Cordless phone keypads

(From: Martin Sniedze (MSniedze@STRNNTS1.telecom.com.au)).

I found that the keypad was always getting wet/oily somehow.  Cleaning with
alcohol only fixed the dialing problem for about a week. A bit of asking at
phone repairer revealed that sanyo has a 'possible' problem with the keypads
absorbing/emitting the oily substance. The repairer sold me a membrane that
goes between the silicon keypad and the PCB, it has carbon pads on the back.
It stops the moisture getting through. It has completely fixed the problem in
my phone (it was done 6 months ago). They should be free.

  7.12) Erratic or noisy telephone equipment

The following applies to normal desk or wall phones, cordless phones, modems,
answering machines, fax machines - essentially anything plugged or wired into
the phone system.

Always check the cords first - especially the one between the handset
and the desk or wall phone itself since it gets a lot of abuse.  Noisy,
intermittent, or totally dead behavior is possible.  In some cases, even the
(electronics) ringer will not work if a wire in this cord is broken as the
ringing signal is generated in the handset and sent back to the ringer unit.
Try jiggling the cord at both ends to see if noise is generated or behavior
changes.  Even permanently wired in cords are replaceable - just take care
to draw a diagram and/or label all the wires before disconnecting the old one.

Bad connections are relatively rare in original ATT dial or Touch Tone
telephones.  These old phones also used very high quality contacts for the
on-hook, dial, and button switches which rarely resulted in problems.
However, with the multitude of modern equipment of all degrees of quality,
bad connections and dirty or degraded switches and relays are very common.

The various microswitches and/or relays for on-hook and other functions
seem to be particularly prone to degredation if not properly specified
in the design.  If phone line pickup or mode switching is noisy or erratic,
this is a likely cause.  Most of these swiches and relays are replaceable
although creativity may be required as an exact match may not be easy
to locate.

To assure that the problem is actually with the particular piece of equipment,
disconnect other devices on the same telephone line.  Aside from the obvious
oversight of a phone that has not been hung up, modems or fax machines that
are not powered on may load the phone lines excessively.  For example, if you
have two PCs with modem connections to the same phone line, the signal quality
on one of them may degrade to the point of reducing the effective transmission
speed, producing an excessive error rate, or not successfully connecting at
all if the other is turned off.  (They may also behave strangely if the
Originate/Answer settings of the modem are set incorrectly - but that is
another matter.)

  7.13) Checking phones and answering machines for electronic problems

Most signal problems will be related to failed components on the telephone
line side of the coupling transformer including components in the phone
line derived power supply (if used).  Phone lines are subject to all kinds
of abuse including lightning strikes (although something significant may
do extensive damage beyond reasonably hope of repair).

* Test all the components on the telephone line side of the coupling
  transformer when line connect, detect, or dial problems are encountered.
  There may be shorted semiconductors due to a voltage spike or just bad luck.

* Some units extract power from the phone line and the rectifiers or other
  related components can go bad.  This can result in either power problems
  (telephone is totally dead) or dialing problems.

* Make sure you are using the proper AC adapter and test it for correct output.

* There could be a defective power supply inside the phone - the regulator
  could be shorted or a filter capacitor could be dried up.  See the chapter:
  "Equipment Power Supplies".

* Check for loose or broken connections - phones get dropped.

* For erratic dialing problems, inspect and clean the keypad and other
  switch contacts.  Also see the section: "Cordless phone problems".

  7.14) Modem problems

First, confirm that your modem settings are correct - reset the modem
to factory defaults using the Hayes AT commands (e.g., AT&F1) or
dip switch settings.  Confirm that your software is set up correctly and
that there are no IRQ or IO address conflicts.

If the modem starts to dial but aborts and hangs up, confirm that you
do not have the wiring of the 'telco' and 'phone' connectors interchanges.

Also see the section: "Erratic or noisy telephone equipment".

Since the phone line is subject to all kinds of abuse, most actual problems
(that are not software related), will be on the phone line side of the
coupling transformer.

* There will be various diodes, transistors, capacitors, opto-isolators, and
  relays for routing the incoming and outgoing signals, or for protection and
  these can fail shorted or open.

* There may be an actual fuse (or more than one) as well - but it will
  probably not look like a common fuse but may be very tiny - more like a
  resistor - or even a surface mount part.  Hopefully, the circuit board will
  be marked 'F1' or 'PR1' or something similar.  Check fuses for opens.

* A lightning strike is likely to obliterate components in the modem beyond
  even your abilities to salvage it.  If it arcs over the coupling transformer
  or just induces a large enough voltage spike, the logic circuitry will be
  history.  However, in many cases, damage is minor.

If you have signal problems - a modem will try to dial out but not
make its way to the phone line, testing on each side of the couping
transformer with a scope or Hi-Z headphones should be able to determine
if the problem is on the logic or phone line side of the device.

Check that the proper AC adapter is being used (if relevant) and that is
is putting out the proper voltage.  Check the internal power supply components
for proper output.  They are often common IC regulators like the 7805 and
are easily tested.  Replacements are inexpensive and plentiful.

(From: Rick Miller (wizkid@mv.mv.com)).

First thing to check: almost all modems have a pair of low-value
resistors (10-20 ohm) between the phone line and their line transformer.

I got a 2400 baud voicemail modem for free this way!  Repaired an
"unrepairable" modem (according to the ACER computer technician! :) )

Replaced a "booger resister" with a real 1/2 job.... had to work hard to
get the leads soldered onto the SMT pads!:)

(From: Jordan Hazen (jnh@aardvark.cen.ufl.edu)).

Yes, in my experience you're much more likely to sustain damage from a
phone-line surge than anything on the power grid.  Modem electronics tend
to be more delicate than the stuff in your power supply.

First thing to check: almost all modems have a pair of low-value
resistors (10-20 ohm) between the phone line and their line transformer.
These are intended to take the brunt of a lightning hit and protect
the electronics upstream.  Traditionally, these have been large,
high-current resistors (like 1/2 watt), but sometimes now they try
to get away with little 1/16-watt surface mount ones that are much more
likely to blow.  Sometimes it's obvious when the resistors have died,
with visible singe marks, pieces blown away(!), etc.  Usually these
fail as an open, resulting in "NO DIALTONE" on trying to connect.

Other vulnerable stuff includes the zener diodes intended to clip down
incoming ring voltage, on the transformer "primary" (telco) side.  These
may fail as a short-circuit.  The ring-detect optoisolator may also blow,
and it can simply be removed if you don't need to take incoming calls.

One of my modems actually had the line relay's contacts welded together by
a lightning hit, so it stayed off-hook constantly!  Check the
isolation transformer for a open coil on either side.  If it's a
high-speed modem, be sure to replace blown transformers with
one of about the same type & quality... the ones on 2400-baud modems
usually had poor frequency response/linearity.

Any damage beyond the transformer will be hard to repair w/o a schematic,
since the surface-mount diodes, transistors, etc. damaged may be hard to
ID for replacement on a surface-mount board.  Something blown in this area
may cause slow/error-prone connections, rather than complete failure.
It happened to be with a particularly nasty strike (the one welding the
line relay closed), transforming a 33.6k modem into a 4800 :-(

Oh, and if the modem's completely dead - no response to AT commands--
you're probably out of luck... this means there's damage to the digital
logic, and it's invariably the 200-pin custom ASICs that blow rather that
74xxx buffers.

(From: jlager@tir.com).

My experiences with the front end of answering machines are welded relay 
contacts mostly.  The symptom is usually holding down the line.

  7.15) Identifying and replacing SMD devices

See the document: "Surface Mount (SMD) Transistor/Diode Cross-reference".
If this does not list your device or it is so fried that no markings survive,
you can usually use some educated guesswork to select a suitable replacement.
SMD types can usually be replaced with normal devices since there is usually
sufficient space.  If there are any other SMD parts with the identical marking,
you should be able to determine pinout (e.g., BCE for transistors - see the
document: "Testing of Semiconductor Devices with a DMM or VOM") and replace
with a general purpose non-SMD type.  I doubt that the specifications of parts
used in telephones or modems are critical.  Even if there are no identical
device, if you can determine the voltages on the pins, you may be able to
guess the type.  The worst that will likely happen if you are wrong is to blow
your replacement device - anything that this will do the rest of the circuitry
has already been done.

Chapter 8) Calculators, Clocks, and Watches

  8.1) Problems with calculators

Small hand held and desk calculators share many of the same afflictions
as hand held IR remote controls.  In particular, battery and keypad
problems are common.

Caution: many devices using LCD displays utilize a printed flex cable to
interconnect the electronics and the display.  Often, this is simply glued
to the LCD panel and possibly to the logic board as well.  The cables are
quite fragile and easily torn.  They are also easily ripped from the adhesive
on the LCD panel or logic board.  If the unit is fairly old, this adhesive
may be very weak and brittle.  Repair or replacement should this occur is
virtually impossible.  The material used for the conductors is a type of
conductive paint that cannot be soldered.  It may be possible to use a similar
material like the conductive Epoxy used to repair printed circuit boards
but this would be extremely tedious painstaking work.  Be extremely careful
when moving any of the internal components - LCD, logic board, keyboard,
battery holder/pack, and printer.

The following problems are likely:

1. Batteries - one or more cells are dead, weak, or have leaked.  Try a new
   set if normal primary cells (e.g., alkaline) are used.  Clean the battery
   contacts.  Where rechargeable (usually NiCd) batteries are used, one or
   more cells may have shorted resulting in a dead calculator or dim display,
   or printer that doesn't work reliably.  See the chapter: "Batteries".
   Test each cell after charging for the recommended time or overnight.
   NiCd cells should be about 1.2 V when fully charged.  If any are 0 V, the
   cell is shorted.  This is particularly likely with a unit that has been
   left in a closet unused for an extended period of time.  It is generally
   recommended that the entire battery pack be replaced rather than a single
   cell as the others are probably on their way out and the capacities will
   not be equalized anyhow.  Rechargeable batteries may be the cause of a
   calculator that does not work properly on AC power as well since they are
   usually used like a large filter capacitor and shorted cells will prevent
   the required DC voltage from being provided to the electronics.  Open cells
   or bad battery connections will prevent this filtering as well and may
   result in erratic operation or other symptoms.  For this reason, it may
   not be possible to run a unit of this type reliably or at all with the
   rechargeable batteries removed.

   Some calculators that use rechargeable batteries like older HPs and TIs
   have a battery pack of 24.4 to 3.6 V with a DC-DC inverter to obtain the
   9 V or so that the NMOS chipset required.  These rarely fail except
   possibly due to leakage of neglected dead batteries.  However, good
   batteries need to be in place for the calculator to work properly.  If
   you are not interested in using these types of calculators on batteries,
   disconnect the DC=DC convertor and substitute a suitable AC adapter.
   Check the voltage and current requirements for your particular model.

2. Keypad - dirt, gunk, and wear may result in one or more keys that are
   intermittent or bounce (result in multiple entries).  Disassemble, clean
   and restore the conductive coating if necessary.  See the document: "Notes
   on the Troubleshooting and Repair of Hand Held Remote Controls".

3. Printer (where applicable) - in addition to replacing the ribbon when
   the print quality deteriorates, cleaning and lubrication may be needed
   periodically.  Dust, dirt, and paper particles collect and gum up the
   works.  Clean and then relube with light machine oil or grease as
   appropriate.   Sometimes, gears or other parts break resulting in
   erratic operation or paper or other jams.  Locating service parts is
   virtually impossible.

4. AC adapter - if the calculator does not work when plugged into the
   AC line, this may be defective - broken wires at either end of the
   cord are very common.  However, shorted cells in an internal NiCd
   battery will likely prevent the proper voltage from being supplied to
   the electronics even when using AC power since the battery is often
   used like a large filter capacitor at the same time it is being
   charged.  Open cells or bad connections to the battery pack may result
   in erratic operation or other symptoms as well.

   Don't overlook the obvious: are you using the proper adapter and if
   it is a universal type, is the polarity and voltage set correctly?
   Check the specifications.  With the proliferation of AC adapters, it
   is all to easy to accidentally substitute one from another device.

  8.2) Repairing a calculator (or other device) with a fried power transformer

There may be a thermal fuse under the outer layers of insulation with is
the only casualty.  It is worth checking out.

(The specific example below is for a Sharp desktop calculator, model CS-1608.
It has a power transformer with 6 wires on the secondary: 2 red, 2 yellow,
1 orange, and 1 brown.)

Power surges, overheating, or connecting a 115 V device to a 220 V line can
all blow the primary.  An overload could also but is likely not the problem.
In my experience, it seems that the transformers in these things are designed
so close to core saturation that excess voltage will not be transferred to
the secondary and even plugging a 115 transformer device like a digital clock
into a 220 line will not kill the logic, but just melts the transformer
primary.  I have a bag full of the things (including a cordless phone) which
were damaged in this manner when someone decided to do a little house
rewiring.  You can guess the rest.

As far as the calculator goes, there are probably 2 sets of secondary
windings probably with centertaps - check it with a multimeter.  I would
guess that the brown is the centertap for the reds and the orange is the
centertap for the yellows but simple tests will confirm or refute this.
One may be for the logic and the other for the printer motors, LCD, who

Obviously, if you can obtain an exact replacement, **this** is truly the
best solution.  Short of this, try to find someone who can measure the
secondary voltages on a working model of this calculator.  Then, you could
replace the transformer with a pair of readily available transformers with
suitable ratings.

If you feel on the lucky side and can at least determine which wires go with
which windings, you could carefully bring up power on one output and see if
there is any response.  It will be at least 5 V.  Examining the regulation
circuitry and filter capacitors could also provide a clue.  Also, you could
determine the ratio of the secondaries by powering one from a low voltage
AC source and measuring the output of the other (assuming the primary isn't
so messed up as to load down the transformer due to shorts).

There are many options besides giving up.

  8.3) Getting inside calculators

Many will have a couple of screws (possibly hidden under rubber feet or inside
the battery compartment) or snaps which will permit the two halves of the case
to be separated.  However, some very popular models are apparently not designed
to be repaired at all:

Note: I have heard that there is a somewhat less destructive (but not any
easier) procedure for getting inside HP48s than that given below but have
not seen it.

(From: A.R. Duell (ard12@eng.cam.ac.uk)).

Have you ever tried to open up an HP48 (or just about any HP calculator later
than the 71B)? It's non-trivial to do non-destructively - these darn things
are held together by pegs that were melted over after the case was assembled.

From memory (and I've never actually done a 48, just the smaller ones) you
have to:

1. Remove batteries, cards, etc.

2. Carefully peel off the metal overlay on the keyboard. This can be done
   without putting a fold in it, but it takes practice.

3. Use a 4 mm (I think) drill held in the fingers to remove the tops of the
   moulded studs holding the case together

4. Pull off the back part of the case.

You can now see the circuit board. It's held down by twisted metal tabs.  The
keyboard is under it, and is held together by a lot more of those infernal
moulded studs.

  8.4) Battery powered digital clock problems

First, try a fresh battery and clean the battery contacts if necessary.
If the battery is very low or dead, well....  When the battery is low
or the connections are bad, the countdown logic may run erratically - fast
as well as slow.  Give it a week and then see if the problem still exists.

If it does - and the error is only a few minutes a week - then an adjustment
may be all that is needed.  If the error is much worse - like it is running
at half speed - then there is a problem in the logic - time for new clock
(or at least a new movement).

There should be a recessed screw for fine speed adjustment accessible from
the back - possibly after a sticker or outer cover is removed.  It may be
marked with a couple of arrows and if you are lucky, with the proper
direction for speed increase and decrease.

Without test equipment, the best you can do is a trial and error approach.
Turn the screw just the tiniest bit in the appropriate direction.  If this
is not marked, use counterclockwise to slow it down and vice-versa.

Wait a week, then readjust if necessary.

If you have frequency counter with a time period mode, you can try putting
it across the solenoid terminals and adjusting for exactly 1.000000 second.
Hopefully the load of the counter will not affect the oscillator frequency.

With sensitive equipment, it may even be possible to do this without any
connections by detecting the fundamental frequency radiation of the quartz
crystal oscillator and adjusting it for exactly 32,768 Hz (most common).

However, keep in mind that the clock's quartz crystal accuracy required to
gain or lose less than 1 minute a month is about +/- 1 part in 43,000 which
may be better than that of your frequency counter's timebase.  One
alternative is to perform the same measurement on a clock that is known
to be accurate and then match the one you are adjusting to that.

  8.5) AC powered digital clock problems

Common problems include totally dead, missing segments in display, running
at the wrong rate, switches or buttons do not work.  (Also applies to the
clock portions of clock radios.)

Note that these is often a battery - possibly just an 9V alkaline type
for backup in the event of a power failure.  If this is missing or dead,
any momentary power interruption will reset the clock.

Although a totally dead clock could be caused by a logic failure, the
most likely problem is in the power supply.  The power transformer may
have an open winding or there may a bad connection elsewhere.  A diode
may be defective or a capacitor may be dried up.

Often, the secondary of the power transformer is center tapped - test
both sides with a multimeter on its AC scale.  Typical values are
6-15 VRMS.  If both sides are dead, then the primary is likely open.
There may be a blown fusable resistor under the coil wrappings but a
burnt out primary is likely.  Although generic replacement transformers
are available you will have two problems: determining the exact voltage
and current requirements (though these are not usually critical) and
obtaining a suitable regulatory (UL. CE, etc) approved transformer -
required for fire safety reasons.

If the transformer checks out, trace the circuit to locate the DC outputs.
These power supplies are usually pretty simple and it should be easy to
locate any problems.

Missing segments in the display are most likely caused by bad connections.
Try prodding and twisting the circuit board and inspect for cold solder

A clock that runs slow on 50 Hz power or fast on 60 Hz power may not
be compatible with the local line frequency since these clocks usually
use the power line for timing rather than a quartz crystal.  This is
actually a more precise (as well as less expensive) approach as the power
line frequency long term accuracy is nearly perfect.  Sometimes there is
a switch or jumper to select the line frequency.

Dirty switches and buttons can be cleaned using a spray contact cleaner.

  8.6) Why is my $2 LED clock so much more accurate than the clock in my $2,000 PC?

Computer clocks use a crystal and are not tied to the AC line - after all,
they have to keep time even when the computer is unplugged.  Cheap digital
clocks that plug into the AC line are extremely accurate - better than anything
else you are likely to have access to short of the broadcast time signal.

The reason for this is that the power line frequency is referenced to an
atomic clock somewhere and its long term accuracy is therefore maintained
to great precision.  Even the short term frequency stability is very good,
changing by at most a small fraction of 1 percent due to variations in
electric load affecting generator speed (U.S national power grid - isolated
areas with local power generators could see much much wider swings).

These clocks may not keep good time if (1) the power line is very noisy, (2)
there is a power outage, or (3) they are broken.  Power line noise on the same
circuit might confuse some clocks, however.  This might happen with light
dimmers or universal motors (e.g., vacuum cleaners, electric drills, etc.) on
the same circuit.

  8.7) Replacing batteries in digital watches

About the only type of service you can expect to perform is battery
replacement but even this can save a few dollars compared to taking
the watch to a jeweler.  The typical watch battery will last anywhere
from a year (alkaline) to 5 years (lithium).  The most likely cause of
a watch that has a dead or weak display, or has stopped or is not
keeping proper time is a weak or dead battery.

The batteries (actually single cells) used in most modern watches (they
used to be called electric watches, remember the Accutron?) are either
alkaline or lithium button cells.  Some are quite tiny.  You will need to
open up the watch to identify the type so that a replacement can be

How you go about doing this will depend on the watch:

1. Screws.  If there are visible screws on either the front or rear, then
   removing these will probably enable the cover to be popped off.  These
   will be teeny tiny star (sort of Philips) head type - use a precision
   jeweler's screwdriver with a Philips head tip.  Immediately put the
   screws into a pill bottle or film canister - they seem to evaporate on
   their own.

2. Snap off back.  This is probably most common.  Look for an indentation
   around the edge.  Using a penknife or other similar relatively sharp
   edged tool in this indentation or at any convenient spot if there is
   none.  It is best to use the wristband mounting rod as a lever fulcrum
   if possible.  The back should pop off.  Note the orientation of the back
   before you set it aside so that you can get it back the same way.

3. Cover unscrews.  The entire back may be mounted in a screw thread around
   its edge in which case you will have to somehow grab the entire back
   and rotate counter clockwise.  An adjustable wrench with some tape to
   protect the finish on the watch may work.

If there is an O-ring seal (like on the space shuttle), be careful not to
nick or otherwise damage it (you know what happens when these are damaged!).

Once the back is off, you will see a lot of precision stuff - though not 
nearly as much as in an old fashioned mechanical watch.  DON'T TOUCH!
You are interested in only one thing - the battery.  Sometimes, once the
back is off, the button cell will simply drop out as there is no other
fastener.  In other cases, one or two more teeny tiny screws will hold it
in places.  Carefully remove these and the button cell.  Replace the screws
so you will not loose them.  Make a note of the orientation of the button
cell - it is almost always smooth side out but perhaps not in every case.

Test the battery with a multimeter.  The voltage of a fresh battery will
be about 1.5 V for an alkaline cell and as high as 3 V for a lithium cell.
A watch will typically still work with a battery that has gone down to
as little as half its rated voltage.

Replacement batteries can be obtained from Radio Shack, some supermarkets,
large drug outlets, electronic distributors, or mail order parts suppliers.
Most likely, you will need to cross reference the teeny tiny markings
on the old battery - places that sell batteries usually have a replacement

Cost should be about $2.00 for a typical alkaline cell and slightly more
for the longer lived lithium variety.

Note: some watches bury the battery inside the works requiring further 
disassembly.  This is usually straightforward but will require additional
steps and some added risk of totally screwing it up.

Install and secure the replacement battery and immediately confirm that
the display is alive or the second hand is moving.  If it is not, double
check polarity.  Sometimes, the back will need to be in place for proper
contact to be made.

Chapter 9) Photographic Equipment

  9.1) Light meters

First check the batteries (if any).  Self powered meters like the old
Westons and their clones could also cause damage to the delicate meter
movement if the light regulating lid was left open in bright light.
Bad connections were also common.  I have repaired the meter movements
on these but it is not much fun.

Hand held light meters are subject to damage from being dropped.

Problems with internal light meters include bad batteries and corroded
battery contacts, dirty or worn potentiometers.

  9.2) Pocket camera repair

It seems that in the last few years, the amount of circuitry crammed into
a compact 35 mm camera has grown exponentially.  Auto-film-advance, auto-
exposure, auto-film speed detection and loading, auto focus, auto-flash
selection, auto-red-eye reduction - just about everything that could be
put under computer control has been.  Next thing you know, the photographer
will be replaced with a auto-robot!

For the most part, modern cameras are very reliable.  However, when something
goes wrong, it is virtually impossible to attempt repair for two reasons:

1. The circuitry is so crammed into a tiny case that access is difficult and
   convoluted.  Many connections are made with relatively fragile flexible
   printed cables and getting at certain parts means removing a whole bunch
   of other stuff.

2. Much of the circuitry is surface mount and many custom parts are used.
   Schematics are nearly impossible to obtain and with all the computer
   control, probably not that useful in any case.  Most parts are not
   available except from the manufacturer and then possibly only to
   authorized service centers.

However, some problems can be addressed without resorting to the camera
repair shop or dumpster.

If the camera is still under warranty, don't even think about attempting
any kind of repair unless it is just a bad battery.  Almost certainly,
evidence of your efforts will be all too visible - mangled miniature screw
heads and damaged plastic seams - at the very least.  There are no easy
repair solutions.  Let the professionals deal with it.

If out of warranty and/or you don't care about it and/or you want an
excuse to buy a new camera, then you may be able to fix certain (very
limited) types of problems.

  9.3) Getting inside a pocket camera

For anything beyond the battery, you will need to get inside.  However,
before you expend a lot of effort on a hopeless cause consider that
unless you see something obvious - a broken connection, bent or dirty
switch contact, or a motor or other mechanical part that is stuck, binding,
or in need of cleaning and lubrication - there is not a lot you will likely
be able to do.  One exception is with respect to the electronic flash which
is usually relatively self contained and simple enough to be successfully
repaired without a schematic.

As with other consumer electronics equipment, getting inside may be a
challenge worthy of Sherlock Holmes.  In addition to many obvious very
tiny screws around the periphery, there may be hidden screws inside the
battery compartment and under the hand grip (carefully peel it back if
that area is the last holdout).  Also see the section: "Getting inside consumer electronic equipment".

This is the time to make careful notes and put all the tiny parts in
storage containers as soon as they are removed.  If you never follow
any of these recommendations for other types of equipment, at least
do so for pocket cameras!

Caution: the energy storage capacitor for the electronic flash may be located
in an unexpected spot way on the other side of the camera.  Accidentally
touching its terminals when charged will be unpleasant to say the least.  Even
if the camera is 'off', some designs maintain this capacitor at full charge.
In addition, it may retain a painful charge for days - with the battery
removed.  Once you get the skins off of the camera (if you ever succeed),
identify this capacitor - it will be about the size of a AA battery - and
put electrical tape over its terminals.

  9.4) Pocket camera problems

The following malfunctions may sometimes be successfully dealt with
without an army of camera repair technicians at your disposal:

Caution: never open the back of a 35 mm camera anywhere there is light of
any kind if there is a chance that there is film inside.  If the camera
is dead, there may be no way of knowing.  Doing this even for an instant
may ruin all of the film that has been exposed and two (usually) additional
pictures.  Opening the back of any other kind of roll film camera will
only expose a few frames as the exposed film usually has a backing (120)
or is inside a cartridge (110).

If a 35 mm camera failed with a roll of film on which you have taken
irreplaceable photographs inside, the pictures can still be saved even if
the camera never works again.  First, wash your hands thoroughly to
remove skin oils.  Use a closet with a tightly fitting door (at night is
better or stuff something in any cracks to block all light - it must be
pitch black) for a darkroom.  Open the back of the camera and carefully
remove the film cassette.  Gently pull the exposed film from the takeup
spool (on the shutter release side of the camera).  It should unwind
easily.  Avoid touching the film surface itself with your fingers (the
edges are ok).  Then, turn the plastic shaft sticking out of the film
cassette clockwise to wind the exposed film entirely into the cassette.

(For items (2)-(4), you will need to get inside of the camera.  See the
section below: "Getting inside a pocket camera".)

1. General erratic or sluggish operation, weak display, camera pooped out
   during film advance or rewind.  Most likely cause: the battery died.

   Test the battery and/or try a new one.  It is possible that the
   battery simply decided to go flat at an inconvenient time or that
   a replacement was defective.  If possible, check the voltage on the
   battery while it is in the camera and the affected operations are
   performed.  If the voltage drops substantially, there could be an
   overload - a motor that is binding or a shorted component.  If the
   camera had been dropped, a mechanical problem is likely.

2. Flash inoperative or excess current drain - runs down batteries.
   Other functions may or may not work correctly.  Most likely cause: a
   shorted inverter transistor.  The electronic flash or strobe is
   usually a self contained module near the actual flash window but
   the energy storage capacitor may be mounted elsewhere - like the
   opposite side of the case.  See the warning below - you could be
   in for a surprise!

3. Mechanical problems with focus, exposure, film advance, or rewind.
   Likely causes: binding due to damage from being bumped or dropped,
   bad or erratic motor operation, gummed up lubrication or dirt, or
   defective driver or control logic.  Locate the motor for each
   function (right, good luck) and confirm that they spin freely and
   move the appropriate gears, levers, cogs, wheels, or whatever.  If
   there is any significant resistance to movement, attempt to determine
   if it is simply a lubrication problem or if something is stuck.  Test
   the motors - see the section: "Small motors in consumer electronic equipment".

4. Auto-film-loading, film advance, or rewind do not operate at all or do
   not terminate.  Most likely cause: defective motor or mechanical problems,
   dirty, corroded, or faulty sensor switches or bad controller.  If there
   is no action or something seems to get stuck or sounds like it is
   struggling, check the battery and motor (see (1) and (3) above).
   Inspect the various microswitches for broken actuators, bent or deformed
   contacts, or something stuck in them like a bit of film that broke away
   from the roll.  Dirt may be preventing a key contact closure.  Sometimes,
   improper cable routing during manufacture can interfere with the free
   movement of a leaf type contact.

5. Exposure too light or too dark.  Check the film speed setting and/or clean
   the contact fingers under the cassette that sense the film (ASA or ISO)
   speed.  Clean the light meter sensor.  Check the batteries,  Look for
   evidence of problems with the lens iris and/or shutter mechanism.  If
   the shutter speed can be set manually, see the section: "Testing of camera shutter speed".

6. Automatic camera not responding to adjustments.  Changing the diaphragm
   or shutter speed usually moves a variable resistor which is part of the
   exposure computer.  If a single control has an erratic effect or no effect,
   its variable resistor is likely dirty or broken.  If none of the controls
   behave as expected, there may be a problem in the actual circuitry that
   computes the exposure.  There is little chance that you could repair such
   a fault.  First, replace the batteries.  Some of these systems will behave
   strangely if the batteries are weak.

Unless there is something obvious - the diaphragm control is not engaging
the lever of the variable resistor, for example, and you care about the
future health of your camera, my recommendation would be to take it in for
professional service.

To successfully repair modern sophisticated compact cameras requires that you
be really really experienced working on teeny tiny mechanisms, have the proper
precision tools (e.g., good quality jeweler's screwdrivers, not just the $2
K-Mart assortment), bright light and a good magnifier, and a great deal of
patience and attention to detail.

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Written by Samuel M. Goldwasser. | [mailto]. The most recent version is available on the WWW server http://www.repairfaq.org/ [Copyright] [Disclaimer]