Notes on the Troubleshooting and Repair of Compact Disc Players and CDROM Drives


Chapter 7) Troubleshooting Guide

  7.1) Instant troubleshooting chart - most common problems and likely causes

The following chart lists a variety of common problems and nearly all possible
causes.  Diagnostic procedures will then be needed to determine which actually
apply.  The 'possible causes' are listed in *approximate* order of likelihood.
Most of these problems are covered in more detail elsewhere in this document.

While this chart lists many problems, it is does not cover everything that can
go wrong.  However, it can be a starting point for guiding your thinking in
the proper direction.  Even if not listed here, your particular problem may
still be dealt with elsewhere in this document.

    7.1.1) CD player is totally dead.

Possible causes:

 1. Power outlet, wall adapter, or batteries are dead (as appropriate).
 2. Damage to line or wall adapter cord or plug.
 3. Bad connections or faulty component in power supply (including blown fuse).
 4. Defective microcontroller.

    7.1.2) CD player is operational but there is no display or partial display.

Possible causes:

 1. Burned out back-light bulb(s).
 2. Bad connections to display panel (totally dead or erratic).
 3. Bad solder connections on display panel (some segment work).
 4. Bad power supply (EL panel filament, driver voltages).

    7.1.3) CD player ignores you.

Possible causes:

 1. Bad connections to one or more buttons or sets of buttons.
 2. Microcontroller failed to reset properly.
 3. Missing/bad voltages from power supply.
 4. Defective microcontroller or other logic.

    7.1.4) Drawer does not open or close.

Possible causes:

 1. Worn, stretched, oily, flabby, belt.
 2. Dirty mechanism or gummed up lubrication.
 3. Stripped gear or other mechanical damage.
 4. Defective motor or bad connections to motor.
 5. Bad drawer/eject button.
 6. Missing/bad voltages from power supply.
 7. Defective microcontroller or other logic.

    7.1.5) Drawer operation is erratic.

Possible causes:

 1. Dirty sense switch contracts or bad connections.
 1. Worn, stretched, oily, flabby, belt.
 2. Dirty mechanism or gummed up lubrication.
 3. Defective motor or bad connections to motor.
 4. Stripped gear or other mechanical damage.
 5. Missing/bad voltages from power supply.
 6. Defective microcontroller or other logic.

    7.1.6) Drawer does not close (or open) completely.

Possible causes:

 1. Worn, stretched, oily, flabby, belt.
 2. Dirty mechanism or gummed up lubrication.
 3. Foreign object like toy, rock, or runaway disc blocking drawer.
 4. Stripped gear or other mechanical damage.
 5. Gear timing is messed up.

    7.1.7) CD changer jams when selecting or ejecting CDs.

Possible causes:

 1. Bad belts, dirt or need for lubrication.
 2. Foreign obejcts, chipped or broken gears, or other mechanical damage.
 3. Messed up gear timing.
 4. Defective sensor (microswitch or opto-interrupter.
 5. Defective motor, driver, or power supply.
 6. Logic or microcontroller problem.

    7.1.8) Spindle table loose or sticks to clamper upon eject.

Possible causes:

 1. Set screw loosened or glue failed holding spindle to motor shaft.
 2. Parts of spindle table broke.

    7.1.9) Intermittent or erratic operation.

Possible causes:

 1. Dirty, scratched, or defective disc.
 2. Dirty lens.
 3. Extended length discs too long for player.
 4. Loading (mechanical) not completed reliably.
 5. Bad connections including missing/erratic optical deck shield.
 6. Cracks in ribbon cable to optical pickup.
 7. Dirty drawer or limit switches.
 8. Power supply or logic problems.
 9. External interference.

    7.1.10) CD player or CDROM drive overheats.

Possible causes:

 1. Excessive ambient temperature - sauna or hot stereo components.
 2. Failing/marginal part in power supply, logic, or optical pickup.

    7.1.11) Operation is poor or erratic when cold:

Possible causes:

 1. Gummed up grease or dirt inhibiting movement until warm.
 2. Condensation on optical components due to temperature change.
 3. Bad connections or dirty contacts affected by temperature.

    7.1.12) Disc is not recognized displaying 'disc', 'error', etc.

Possible causes:

 1. Disc loaded upside-down.
 2. Transportation lock engaged.
 3. Dirty, scratched, or defective disc.
 4. Dirty or damaged objective lens.
 5. Loading (mechanical) not completed reliably.
 6. Damaged lens suspension or damaged lens cover preventing free movement.
 7. Dirt, gummed up lubrication, or damage in sled drive mechanism.
 8. Dirty/defective limit switch or sensor.
 9. Defective spindle motor.
10. Spindle table height incorrectly set.
12. Bad component in optical pickup.
13. Cracks in ribbon cable to optical pickup.
14. Need to adjust servo (or less likely, optical) alignment.
15. Faulty power supply, electronics, or control logic.
16. Bad connections including missing/erratic optical deck shield.
17. External interference.

    7.1.13) Disc spins in wrong direction or overspeeds and is never recognized.

Possible causes:

 1. Disc loaded upside-down.
 2. Dirty, scratched, or defective disc.
 3. Dirty or damaged objective lens.
 4. Tracking or CLV servo out of adjustment or faulty.
 5. Bad component in optical pickup.
 6. Microcontroller or control logic problems.
 7. Bad connections or defective ribbon cable to optical pickup.

    7.1.14) Pickup attempts to reset past inner track.

Possible causes:

 1. Dirty or defective limit switch, bad connections to it, or its electronics.
 2. Broken parts preventing limit switch from being activated.
 3. Tracking servo out of adjustment or faulty.
 4. Microcontroller or logic problems.

    7.1.15) Player won't let you go near it and/or use your favorite lamp.

Possible causes:

 1. Missing optical deck shield, ground strap, or other connection.
 2. Outside interference.

    7.1.16) Seek operations take too long or fail to complete.

Possible causes:

 1. Dirty, scratched, or defective disc.
 2. Transportation lock engaged.
 3. Dirty or damaged objective lens, suspension, obstruction, etc.
 4. Tracking or CLV servo out of adjustment or faulty.  
 5. Mechanical problems with sled movement.
 6. Faulty sled motor or drive IC.
 7. Faulty control logic.
 8. Bad flex cable to optical pickup.

    7.1.17) Search, seek, or play starts correctly, then loses time or position.

Possible causes:

 1. Dirty, scratched, or defective disc.
 2. Dirty or damaged objective lens, suspension, obstruction, etc.
 3. Tracking or PLL servo out of adjustment or faulty.
 4. Stuck button.
 5. Defective sled motor drive IC.
 6. Faulty control logic.

    7.1.18) Short distance skipping.

Possible causes:

 1. Dirty, scratched, or defective disc.    
 2. Dirty or damaged objective lens, suspension, obstruction, etc.
 3. Fine tracking servo out of adjustment or faulty.
 4. Weak laser or other defective part in the optical pickup.

    7.1.19) Playback gets stuck (rapid repeat).

Possible causes:

 1. Dirty, scratched, or defective disc.    
 2. Dirty or damaged objective lens, suspension, obstruction, etc.
 3. Dirt, gummed up lubrication, or damage in sled drive mechanism.
 4. Transportation lock engaged.
 5. Need for servo alignment.

    7.1.20) Occasional long distance skipping or repeating.

Possible causes:

 1. Dirty, scratched, or defective disc.
 2. Dirty or damaged objective lens, suspension, obstruction, etc.
 3. Dirt, gummed up lubrication, or damage in sled drive mechanism.
 4. Transportation lock engaged.
 5. Need for servo alignment.

    7.1.21) Player gets stuck at approximately same time on multiple discs.

Possible causes:

 1. Dirt, gummed up lubrication, or damage in sled drive mechanism.
 2. Sled reaching mechanical stop with extended length (>74 minute) disc.
 3. Transportation lock engaged.
 4. Need for servo alignment.
 5. Defective spindle motor.

    7.1.22) Various tracking problems on portions of discs:

Possible causes:

 1. Dirty, scratched, or defective disc.
 2. Faulty spindle motor.
 3. Misalignment of spindle table and sled track.
 4. Need for CLV adjustment.

    7.1.23) Repetitive noise at disc rotation rate.

Possible causes:

 1. Dirty, scratched, or defective (possibly warped) disc.
 2. Dirty or damaged objective lens, suspension, obstruction, etc.
 3. Loose spindle or foreign material on spindle table.
 4. Disc not firmly clamped.
 5. Bent spindle.
 6. Excessive spindle runout due to worn bearing.
 7. Need for servo alignment.
 8. Weak laser or other component in optical pickup.

    7.1.24) Audio muting, noise, or distortion.

Possible causes:

 1. Dirty contacts on RCA jacks on CD player or amp.
 2. Bad connections to RCA jacks.
 3. Dirty/defective muting relay contacts.
 4. Defective components in the analog circuitry (final filter, muting, amp).
 5. Faulty power supply (for audio circuits if used).
 6. Dirty controls (probably on amp unless problem is with the headphones).

  7.2) General inspection, cleaning, and lubrication

The following should be performed as general preventive maintenance or when
erratic behavior is detected.  The lens and its suspension, turning mirror,
drawer mechanism, spindle, and sled drive should be checked, and cleaned and/or
lubricated if necessary and appropriate.

You will have to get under the clamp to access the lens and spindle on drawer
loading models but the lens and its suspension, at least, should be readily
accessible on portable CD players with pop-up doors.  These types can collect
a lot of dust, dirt, and even fingerprints!  Realistically, you probably won't
do any of this for component CD players, CDROM drives, or other drawer loading
models until something goes wrong! :-)  (I don't blame you - getting one of
those out from the tangle of entertainment center wiring, dusting it off,
removing the cover, disassembling to whatever level is needed, and so forth
can be a royal pain.)

Cleaning the objective lens and turning mirror (if accessible) are the most
important general maintenance that can be done.  Even minor contamination of
their optical surfaces can easily result in 50 percent reduction in the
returned signal - and all sorts of problems.

* Objective lens - Carefully clean the lens assembly.  Be gentle! The lens
  is suspended by a voice coil actuated positioner which is relatively
  delicate.  A CD lens cleaning disc is nearly worthless except for the most
  minor dust as it will not completely remove grease, grime, and condensed
  tobacco smoke products (yet another reason not to smoke!) and make matters
  worse by just moving the crud around.

  First, gently blow out any dust or dirt which may have collected inside the
  lens assembly.  A photographic type of air bulb is fine but be extremely
  careful using any kind of compressed air source.  Next, clean the lens
  itself.  It is made of plastic, so don't use strong solvents.  There are
  special cleaners, but isopropyl alcohol us usually all that is needed for CD
  players and VCRs.  (91% medicinal is acceptable, pure isopropyl is better.
  Avoid rubbing alcohol especially if it contains any additives.)  However,
  sometimes, a drop of water will be needed to dissolve sugar based crud.
  There should be no problems as long as you dry everything off (gently!)
  reasonably quickly.  DO NOT LUBRICATE!  You wouldn't oil a loudspeaker,
  would you?

  You cannot generally get to the bottom surface of the lens but this isn't
  nearly as exposed as the top surface so it usually isn't a problem.

  Do NOT use strong solvents or anything with abrasives - you will destroy the
  lens surface rendering the entire expensive pickup worthless.

* Now, inspect the lens.  When clean, the lens should be perfectly shiny
  with a blue tinge uniform over the central surface.  Minor (barely visible)
  scratches will probably cause no harm but any major scratches may result in
  erratic tracking or total inability to even read the disc directory.  The
  pickup (or lens assembly) will need to be replaced in this case.

  It is easy to be misled into thinking that there are serious problems at
  the root cause of discs not being recognized, audible noise (CD players) or
  data errors (CDROM or optical drives), and tracking problems like skipping,
  sticking, or seek failures.  However, in many cases, it is simply a dirty
  lens!  Even people who repair CD players regularly may make an incorrect
  diagnosis since many of the symptoms **are** similar to those caused by a
  bad laser, spindle motor, or major logic failure.

* Turning mirror or prism.  If you can get to it under the lens without
  disturbing anything, clean this as well using the same procedure.  Cleaning
  this may be at least as important as the lens.  Unfortunately, the turning
  mirror may not be accessible without major (and difficult) disassembly.

  Cleaning the turning mirror is nearly as important as cleaning the lens
  (especially for Sony pickups apparently since it is relatively exposed).

  However, for the typical Sony pickup (also used in Sony PlayStations and by
  AIWA and other manufacturers), it is really pretty easy.  First, remove the
  black protective cover by prying the clips out on either side.  Use a
  toothpick or Q-tip stick to GENTLY lift up on the lens assembly taking care
  not to damage any of the fine wires.  Blow out any dust using an air bulb.
  There will be just enough room to get a Q-tip in between the lens and mirror.

  Note: The turning mirror is not silvered so don't expect a normal mirror
  appearance - it looks just like a piece of glass.  However, it is coated to
  be an excellent reflector for the 780 nm IR laser light.

  Of course, this procedure doesn't get to the beam splitter, photodiode, or
  laser diode window - but you can't have everything! :-)  Fortunately, these
  are usually better protected and less likely to collect dust and grime.

* Lens suspension for focus and tracking.  Check this for free movement
  and damage:

  - Focus: The lens should move up and down without sticking (turn the player
    or pickup upside-down carefully to watch the lens move without power and/or
    move it gently with a dry Q-tip).  It should remain parallel to the deck
    throughout its range and return to the center or just below center when
    released.  However, it is hard to say just how far below the center is
    enough to consider it bad.  Even a bottomed out lens might work - the
    focus servo can correct to a large extent - but could result in more
    susceptibility to skipping or other erratic operation particularly with
    less-then-perfect discs.  Also, see the section: "Comments on Sony KSS pickup suspension problems".

  - Tracking: Use a Q-tip to gently move the lens toward and away from the
    spindle.  It should move easily without sticking and remain parallel to
    the deck.  When released, it should return to approximately the middle

  A suspension which fails any of these tests probably means replacement of
  the pickup - or CD player - is needed.  However, the lens with its suspension
  is one of the few components of the optical pickup assembly that may be
  replaceable - at least in principle.  See the section: "Interchangeability of components in the optical pickup".

* Spindle bearing - Check the spindle bearing (this is primarily likely to
  cause problems with repetitive noise).  There should be no detectable side
  to side play.  I.e., you should not be able to jiggle the platform that the
  CD sits on.  If you find that the bearings are worn, it is possible to
  replace the motor (about $10 from various mail order houses), though removing
  and replacing the disc platform may prove challenging as a result of the
  usual press fit mounting.

  The focus servo can compensate for a vertical movement of the disc
  surface of 1 mm or so.  A small bearing side play can easily cause
  larger vertical errors - especially near the end (outer edge) of the disc.
  Even if you are not experiencing problems due to bearing wear, keep your
  findings in mind for the future.

  Sometimes there is a bearing runout adjustment screw on the bottom
  of the spindle if the spindle is not driven by a standard permanent
  magnet motor.  I have seen this in a Sony Discman which had a custom
  motor assembly. A small tweak to this may fix a marginal spindle problem.

To access the drawer mechanism and sled drive in component units, you will
probably need to remove the optical deck from the chassis. It is usually
mounted by 3 long screws (one of which may have a grounding doodad - don't
lose it.  In portables and CDROMs, the bottom panel of the unit will need
to be removed.  Try not to let any of the microscrews escape!  A good set of
jeweler's screwdrivers is a must for portables.

* Drawer mechanism (if present) - Check for free movement.  Test the belt for
  life - it should be firm, reasonably tight, and should return to its original
  length instantly if stretched by 25% or so.  If the belt fails any of these
  criteria, it will need to be replaced eventually, though a thorough cleaning
  of the belt and pulleys with isopropyl alcohol (dry quickly to avoid damaging
  the rubber) or soap and water may give it a temporary reprieve.

  Also, check the gears and motor for lubrication and damage and correct as
  necessary.  Clean and lubricate (if necessary) with high quality light
  grease suitable for electronic mechanisms such as MolyLube or Silicone
  grease.  A drop of light oil (electric motor oil, sewing machine oil) in
  the motor bearings may cure a noisy or dry bearing.

* Sled drive - check the components which move the pickup including (depending
  on what kind of sled drive your unit has) belt, worm gear, other gears, slide
  bearings.  These should all move freely (exception: if there is a lock to
  prevent accidental damage while the unit is being transported the pickup may
  not move freely or very far).  Inspect for damage to any of these components
  which might impede free movement.  Repair or replace as appropriate.  Clean
  and lubricate (if necessary) with just a dab of high quality light grease
  suitable for electronic mechanisms such as MolyLube or Silicone grease).  A
  drop of light oil (electric motor oil, sewing machine oil) in the motor
  bearings may cure a noisy or dry bearing.  Also see the section: "Testing the sled for mechanical problems".

Try to play a disc again before proceeding further.  I guess you have
already done this.

  7.3) Lubrication of CD players

The short recommendation is: DO NOT add any oil or grease unless you
are positively sure it is needed.  Most moving parts are lubricated
at the factory and do not need any further lubrication over their lifetime. 
Too much lubrication is worse then too little.  It is easy to add a drop
of oil but difficult and time consuming to restore an optical pickup
that has taken a bath.

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.

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.

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.
In a CD player or CDROM drive, there are a very limited number of failures
specifically due to lubrication.

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.  If the
old lubricant is gummed up, remove it and clean the affected parts
thoroughly before adding new oil or grease.

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!

Chapter 8) General System Problems

  8.1) CD player is totally dead

Check input power, power cord, fuse, power supply components.  Locate the
outputs of the power transformer and trace them to the rectifiers and
associated filter capacitors and regulators.  While the actual voltages
will probably not be marked, most of the power in a CD player will be
typically between +15 and -15 VDC.  Sometimes, the voltage ratings of the
filter capacitors and/or regulators will provide clues as to correct power
supply outputs.   Don't forget the obvious of the line cord, line fuse
(if present), and power switch - or outlet.  Most component CD players use
linear power supplies so troubleshooting is straightforward.

Portables CD players and CDROM drives often use DC-DC converters to produce
the various voltages required, and these are much more difficult to
troubleshoot even with a complete service manual.  Doing anything other than
checking for shorted or open components is virtually impossible without an
accurate schematic.  If an incorrect power adapter was used (or this happened
when you plugged or unplugged the power connector of a CDROM drive with power
on - a no-no), then major damage can result despite the various types of
protective measures taken in the design.  However, check for the obvious - a
blown fuse on the mainboard near the power connector.  These may be
picofuses(tm) which look like little green resistors, IC Protectors which look
like tiny transistors with only 2 legs, or something else marked F, ICP, etc.
You might get lucky.

I inherited a Sony Discman from a guy who thought he would save a few bucks and
make an adapter cord to use it in his car.  Not only was the 12-15 volts
from the car battery too high but he got it backwards!  Blew the DC-DC
converter transistor in two despite the built in reverse voltage protection
and fried the microcontroller.  Needless to say, the player was a loss but the
cigarette lighter fuse was happy as a clam!

Moral: those voltage, current, and polarity ratings marked on portable
equipment are there for a reason.  Voltage rating should not be exceeded,
though using a slightly lower voltage adapter will probably cause no harm
though performance may suffer.  The current rating of the adapter should
be at least equal to the printed rating.  The polarity, of course, must be
correct.  If connected backwards with a current limited adapter, there may be
no immediate damage depending on the design of the protective circuits.  But
don't take chances - double check that the polarities match - with a voltmeter
if necessary - before you plug it in!  Note that even some identically marked
adapters put out widely different open circuit voltages.  If the unloaded
voltage reading is more than 25-30% higher than the marked value, I would
be cautious about using the adapter without confirmation that it is acceptable
for your player.  Needless to say, if the player behaves in any strange or
unexpected manner with a new adapter, if any part gets unusually warm, or if
there is any unusual odor, unplug it immediately and attempt to identify the
cause of the problem.

See the document: "Notes on the Troubleshooting and Repair of Audio Equipment
and other Miscellaneous Stuff" for more info on linear power supplies.  See
the document "Notes on the Troubleshooting and Repair of Small Switchmode
Power Supplies" for more info on DC-DC convertors.

  8.2) CD player is operational but there is no display or partial display

Where the display is very dim or totally out, suspect one or more burned out
bulbs for the backlight.  Sometimes the display uses miniature incandescent
lamps and these burn out.  Usually, alternatives to the high priced exact
replacement bulbs can be located.  Test the bulbs with an ohmmeter.  Measure
the voltage across the light bulb connections and then replace the bulb with
one of about 25-50% higher voltage.  These may not be quite as bright but
should last forever.

If the light bulbs are not at fault or there are no light bulbs, then check
for power to the display including bad connections or connectors that need
to be reseated.  There could also be a power supply (e.g., missing voltage
to the filament or segments for a vacuum fluorescent display) or driver

If only portions of the display are bad - some segments on multiple digits,
for example, check for bad connections to the driver chip.  The displays
are usually multiplexed meaning that a single output of the driver chip
actually is used for the same segment in multiple digits or even apparently
unrelated words or icons.  Thus, a single failure can result in strange
display behavior.  If no bad connections are found, the driver chip or actual
odisplay could be at fault.  Since the player works otherwise, unless you are
a purist, it make sense to just leave it alone.

In the case of a portable or car CD that uses a 'zebra stripe' type rubber
compression connector, cleaning the rubber piece, display, and circuit board
with alcohol and reinstalling may solve the problem.  If it uses a glued on
printed flex cable, DO NOT attempt to remove it.  Take extreme care when
working on such equipment as it is virtually impossible to repair a cable
of this type should it tear or pull free.

  8.3) CD player ignores you

Symptoms are that the display comes up normal when power is turned on
but all (or certain) commands are ignored.

This could mean several things:

* Front panel problem - one or more buttons are not responding.  Reseat
  internal cables, clean or replace offending push button switches.  If
  your CD player has a remote control, see if it operates correctly.

* Reset failure - the player has failed to reset properly and is not ready
  for user input.  Try pulling the plug for a couple of minutes to see if
  it will reset.  Check power supply voltages, clean and reseat internal

* Controller and/or driver electronics for the affected functions are
  defective.  Check power supply voltages, reseat internal connectors.

For all but the first one, a service manual will probably be needed to
precede further if the problem is not with a bad power supply or bad

  8.4) Drawer does not open or close

If the drawer doesn't open when the front panel button is pressed, listen
for motor attempting to open the drawer.  If you hear it whirring but nothing
happens, check for an oily/loose belt or other mechanical fault.  The belt
may be cleaned for temporary repair, replacement will be needed eventually.
If there is no attempt, motor, control chip, or front panel pushbutton (try
with the remote if you have one to eliminate this possibility) could be bad.
Sony players seem to have a built in timer that triggers the belt to go bad
after the warranty runs out.  Also see the section on "Small motors in CD players".

  8.5) Drawer operation is erratic

You are about to remove your favorite CD but the player beats you to it, 
closes the drawer, and starts playing it over again.  Or, the drawer
reverses course halfway out.  Or, the drawer motor continues to whir
even after the door is fully open or closed and the front panel is
then unresponsive.

This is usually due to dirty contacts on the door position sense switches.
There are usually 3 sets of switch contacts associated with the drawer
mechanism.  If any of these get dirty, worn, or bent out of place, erratic
operation can result:

* Drawer closed sense switch - dirty contacts may result in the drawer motor
  continuing to whir after the door closes and the front panel may then
  be unresponsive.  Eventually, the drawer may open on its own.

* Drawer open sense switch - dirty contacts may result in the drawer motor
  continuing to whir after the door opens and the front panel may then
  be unresponsive.  Eventually, the drawer may close on its own.

* Drawer pushed sense switch - most CD players allow the user to start play
  by gently pushing on the drawer which depresses a set of switch contacts.
  If these are dirty, the result may be the drawer deciding to close on its
  own or reversing direction in the middle of opening or closing.

The solution to all these problems is usually to simply locate the offending
switches and clean their contacts.  These switches contacts are usually not
protected from dust, dirt, and grime so that these types of problems are
quite common.

If the drawer simply doesn't respond to your wishes - sometimes, there may be
a bad belt or bad motor.

* Sometimes, how long the player has been powered will affect the 'stickiness'
  of the belt - leave it on long enough and the belt will loosen and be too
  weak to operate the drawer.  See the section: "Drawer does not open or close".

* The drawer motor may have a 'dead spot' or be partially shorted.  See the
  chapter: "Motors and Spindles".

  8.6) Drawer does not close (or open) completely

This is a symptom that may not be obvious.  The drawer may appear to close
but a loose or oily belt can prevent the mechanism from completing the close
cycle.  This can result in erratic behavior since the disc clamping action
is often controlled by the movement - sometimes not recognizing disc,
sometimes just opening the drawer, or more subtle things like tracking
problems, etc.  Clean the belt and see if there is any improvement.  Belt
replacement will be necessary eventually.  Check for gummed up lubrication
as well.

If it goes through the motions of closing and then stops short without
any further sounds, a gear may have jumped a tooth or broken some.  The
result is either that the mechanism is now incorrectly timed or not able
to complete the operation.  Examine the mechanism closely for broken
parts.  Cycle it manually by turning the appropriate motor pulley or gear
to see if the drawer gets hung up or is much more difficult to move at
some point.

If it continues to make a whirring sound after the drawer stops, there might
be some other kind of mechanical damage resulting in an obstruction or really
gummed up lubrication not allowing the operation to complete.

If you have small kids around, don't overlook the possibility that your CD
player is being used as a storage cabinet!  A favorite toy, rock, gummy bear,
jelly bean, or other organic or inorganic object may have found its way into
the CD compartment.  Or, perhaps, someone, somehow, managed to lodge a disc
inside despite the best efforts of the CD player's designers.  (This might
happen if it was transported upside-down, for example).

  8.7) CD changer jams when selecting or ejecting CDs

Unfortunately, this is the sort of problem one has to see to be able to make
specific recommendations.

* Check for flabby/oily belts (if any), dirt, or and gummed up lubrication.

* Double check that it is in good condition mechanically - no chipped gear
  teeth or broken parts.

* Gear timing may be messed up (especially if someone worked on the unit
  previously though I don't know which, if any CD changers, depend on this for
  proper operation).

Try to cycle the mechanism manually by turning the appropriate motor shafts.

* A defective sensor - either a microswitch or opto-interruptor - can result
  in improper commends being issued to the motors.

* Check for bad connections, defective motors and drivers, and power problems,
  if movement is weak, erratic, or non-existent.

* A logic problem is also possible but not very likely.

Get a bunch of garbage AOL or MSN (your choice) CDs to experiment with - it
should be able to cycle them just fine but the audio may sound weird :-).
(Hint: Turn the volume way down!)  Then, try to determine exactly what it is
trying to do and how it screws up.

For auto changers where one disc doesn't come out:

(From: Tony (tony@buffnet.net)).

Try removing all the CDs from the magazine and inserting the empty magazine
into the changer. Now turn on the unit and see if the cd goes back into the
magazine. If it does not, look for a reset button on the changer. It will be
a tiny hole near the eject button that requires a paper clip or toothpick to
be inserted to contact the switch. Try pushing this with the magazine
inserted. If you do not see a reset switch on the changer look for one on
the face of the radio or, if it is a removable face radio, remove the face
and see if there is a switch on the panel behind the face and try that. If
all of this does not work, the changer will have to be disassembled for the
CD to be removed. If the unit is under warranty, take it back so as not to
void your warranty by disassembling the unit.

  8.8) Spindle table loose or sticks to clamper upon eject

When you remove the CD, you may have an added surprise - the platform upon
which the CD sits pops off as well, possibly jamming everything.  There may
also be startup and spindown problems.

Various models use different techniques to fasten the spindle table to the
motor shaft but this is strictly a mechanical problem.  Either a set screw
has worked loose, adhesive has weakened, or a press fit has come undone.

If there is no set screw, a drop of Epoxy may be what is needed.  However,
height is important to guarantee proper focus range so some care will be
needed if there no definite stop.  The disc and rotating clamper magnet
must be clear of any fixed structures and the correct distance from the
optical pickup.  Where something irreversible is involved like adhesive,
checking the service manual is highly recommended - the specification is
usually .1 mm accuracy.

A loose spindle table may also result in continued spinning upon eject or
sluggish or noisy startup or seek since the if the spindle is loose, the
motor will not be able to properly control disc speed during speed changes.

  8.9) Intermittent or erratic operation

When a CD player appears to have a mood problem - playing fine sometimes or
for only part of a disc or aborting at random times, there can be several
possible causes including a dirty lens, dirty or worn interlock switch or bad
connections to interlock switch (mainly portables and boomboxes), flex cable
with hairline cracks in one or more conductors (or just misrouted and close to
a metal part of the chassis!), other bad connections, marginal power supply,
defective or extended length disc.

* Dirty, scratched, or defective CD - confirm that the CD is not the problem.
  Clean the disc and/or try another one.  However, not all CDs are created
  equal.  Both the overall quality of the information layer and plating as
  well as the amount of lead-in and blank space between music tracks varies.
  Thus, where some aspect of the CD player's optics or electronics is not
  perfect - or even variations in the microcontroller's programming - can
  result in the player not properly dealing with some discs.  The use of
  CD-Rs represents even more variability since they are increasingly written
  on low cost equipment of questionable quality.  

* Dirty lens - a player that accepts some discs and not others or accepts
  discs sporadically may simply need its eyeglasses cleaned.

* Extended length discs - some players will simply not play discs which
  exceed about 74 minutes (the legal limit for CD playing time) to the end
  (or possibly at all).  Such CDs may be as long as 78 or 80 minutes or more.
  This means that certain aspects of the CD specifications were compromised.
  Both mechanical and electronic problems are possible.  See the section:
  "Problems with extended length discs".

* Mechanical - oily, flabby belts preventing full drawer closing or gummed
  up lubrication on the sled (may fail depending on ambient temperature.
  For example, if the music gets stuck at about the same time on every disc,
  then there may be gunk on the end of the sled track preventing the sled
  from moving any further.  This is especially likely if you just purchased
  a disc with an unusually long playing time - it has nothing to do with
  the musical tastes of the CD player!  (There was this Chinese restaurant
  where the Chinese cooking grease apparently collected on the unused end
  portion of the sled track and when they tried to play an extra long CD.....)

* Bad connections - there are often many little connectors used to get
  signals and power between the optical deck and main circuit board.  These
  are usually cheaply made and prone to failure.  Wiggling and reseating
  these may cure these problems.  There may even be bad solder connections
  on the pins of connectors or board mounted switches.  Slight flexing or
  just expansion and contraction may result in intermittent shutdown or
  other problems.  These problems are more likely with portables and
  boomboxes which may get abused.

  The connectors for any flex cables are particularly prone to developing
  erratic contact.  Where a locking bar is used, pull it up to release the
  cable; remove, clean, and reinsert the cable; and press the locking bar
  firmly into place may help.  Where there is no lock, gently pull the cable
  out of the connector, clean, and install.  I have seen problems of this
  type on a couple of CDROM drives - portable and component CD players use
  the same types of cables.

* A missing shield between the analog ground and the optical deck can result
  in all kinds of erratic behavior.  If these weird problems started after
  you had the player apart for some reason, check that you replaced the
  grounding strap or metal strip and/or didn't accidentally disconnect  or
  break any shield connection on the ribbon cable to the optical deck.

* Cracks in ribbon cable - The moving and fixed parts of the optical pickup
  are often joined with a printed flexible cable.  Constant flexing may
  cause one or more of the copper traces to crack.  This may show up as
  an inability to get past a certain point on every disc - the player may
  shut down or start skipping at around 23 minutes into every CD.

* Dirty switches - oily film or oxidation may be preventing any of the
  limit or interlock switches from making reliable contact.  If this is the
  case, the player may stop at random times, fail to accept a disc, close the
  drawer without your permission, etc.  Use contact cleaner and typing paper
  to clean the contacts.  Disassembly may be required for enclosed switches.

* Power supply or logic problems are also possible but rare.  However, if
  you have a scope, check the power supply outputs for ripple - a filter
  capacitor may have dried up and lost most of its capacitance.

* External interference from a powerful local radio station (probably AM
  but could also be CB or a ham operator), light dimmer, or other source.
  Sometimes reversing the AC plug, repositioning the equipment, or using
  higher quality cables may help.  Unfortunately, there are often no easy
  solutions to these sorts of problems.  A missing or broken optical deck
  shield ground (see above) could make the player more susceptible to this.

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