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


  11.14) Repairing flexible printed cables

It seems that more and more consumer devices from pocket cameras to
laptop computers are being built with miniature multiconductor flexible
printed cables.  Very often one or more traces to develop hairline cracks
due to repeated flexing.  In addition, damage from moving circuit boards
and modules during servicing is all to common.

Needless to say, repairing any kind of flex cable is a real pain.
I have succeeded by carefully scraping the plastic off with an Xacto
knife and then soldering fine wire (#30 gauge wire wrap for example)
to the traces.  This presumes that the conductors on your cable will
even take solder.  I then cover up the joints with a flexible sealer
for electrical and mechanical protection.

However, you need to make sure that the wire you use can be flexed or that the
joint is set up in such a way that the wire does not flex much - else
you will just end up with broken wires pretty quickly.

Here is another alternative if the flexing of the cable prevents the use of
ordinary wire for jumpers:  Find a piece of somewhat similar flex cable
cable from a dead piece of equipment.  Use it to jumper across the high stress
area and then solder it to the other cable with short wires if necessary.
Then coat the connections as above.

Soldering from end point to end point if possible may be preferable.
Even going to only one endpoint would reduce the risk of immediate damage
and reliability problems in the future.

With multiple traces broken or damaged, you are probably better off replacing
the cable entirely.  With the typical flex cables found in CD players, there is
often no way to repair a large number of broken traces and retain your sanity.

  11.15) CD player whine

CD players are generally nearly silent during play (though they may make
a variety of whirring and clicking noises when loading discs, initializing,
or seeking).  The only sound normally eminating from inside the machine
during play might be a very faint gritty noise from the focus and tracking

Thus, a sustained whine would generally be considered abnormal.

(Portions from: Larry Sirignano (sirig@esslink.com)).

There are two likely causes:

1. Worn spindle motor bearings can result in a high pitched whine.  In this
   case, adding a drop of oil may quiet it down temporarily but replacement
   will eventually be needed.

2. The whining noise may be the laser/chassis assembly resonating with the CD
   as it spins.  Depending on the model, there is a cure - adding a weight or 
   damping material to the pickup or the chassis to change the resonant 

   To confirm that this is your problem, gently rest your finger on the
   rotating clamper disk and/or other parts of the optical deck while it
   is whining - the whine should change or disappear.  If you can locate a
   particularly sensitive spot, try gluing a piece of heavy rubber to this
   location (even if it is the clamper disk) with rubber cement.  If this
   solves the whine problem, confirm that discs seek and play correctly for
   all tracks before buttoning it up.

For more details on Sony problems, see the section: "Audio whine (not from speakers) and/or muddy sound with Sony CD players".

(From: Joel B. Levin (levinjb@gte.net)).

If this were the problem it would be highly dependent on the CD's speed of
rotation, which varies as the disc is played.  If it always happened N minutes
into the disc and went away a few minutes later as the disc slowed down (and
came back if you repeated the track) I would consider that definitive of a
resonance problem.

(From: Mark Z. (Imzacharias@aol.com)).

I would try lubricating the shaft of the spindle motor, and check to see if the
motor brushes might be partially shorted.  (not to worry you at this early
stage, but sometimes Sony pickups, especially the KSS-240 and KSS-212 and 213,
have resonance problems, often just  as the disc is coming to speed.) This is
the subject of at least a couple service bulletins.  Can often be heard as a
whistling tone coming from the mechanism usually intermittent, and can be
observed in the focus error and tracking error lines as a sine wave overriding
what should be essentially a random noise signal.  Occasionally the resonance
gets so pronounced the disc won't even spin up.

  11.16) Objective lens popped out

Don't expect to see this one too often.  However, on some Pioneer changers in
particular, where the pickup is mounted upside-down, excessive heat, age,
long use with warped discs, or just bad luck, has apparently resulted in the
adhesive holding the objective lens in place to come unglued, as they say :-).
(See below.)

The best solution is to replace the entire pickup.  However, you have nothing
to lose by attempting to reattach the lens IF you can locate it AND its optical
surfaces are undamaged from the ordeal.  If either of these is not the case,
you will probably have to install an entire new pickup.  Swapping of a lens
from another player is even less likely to work unless it uses a similar
pickup from the same manufacturer and then only with great pain.

It is essential to line up the lens in EXACTLY the same position as it was
originally in terms of centering as well as the same orientation to have any
chance of success:

* The lens must be centered for the return beam to be properly aligned with
  the photodetector array.

* Some lenses are astigmatic (not circularly symmetric) to implement the focus
  servo (rather than using a separate cylindrical lens for this purpose).
  Thus, their orientation is also critical.  When this is the case, there will
  be a reference on the lens for this purpose.  On Sony pickups, for example,
  there is a flat filed on one edge of the lens.  (You always wondered why
  the lenses in all your Sony CD players appeared to be 'damaged', didn't
  you?)  However, I do not know if this is its function as the lens does not
  appear astigmatic from eyeball inspection.

Alignment isn't so bad if you can see the failure line in the old glue.  If
not, you will need to compare the orientation with an intact sample of a
pickup from the same manufacturer that uses a similar optical configuration.
Just guessing will NOT work!

Carefully position the lens and put the tiniest drop of adhesive such as
windshield sealer, Duco Cement, or Krazy Glue (if you have mastered that
disaster!) at three points roughly equally spaced around the edge of the lens.
Do not let any glue run down into the suspension or elsewhere.  Once the glue
has set, reinstall the pickup and try it.  If behavior seems reasonably normal,
put a tiny bead of adhesive all around the lens to anchor it securely.  Some
servo adjustments and/or optical alignment may still be needed to correct for
the slight shift in lens position that is unavoidable from this surgery.

(From: Dave (albrecht@se-iowa.net)).

A local radio station uses about 20 Pioneer PD-M510s.  I've been replacing a
lot of lenses that are starting to fall out.  I usually do a "shake" test,
recover the lens and glue it back in place. Not bad considering most haven't
been shut off and have played for 4 years now.

  11.17) Testing the optical pickup

See the special section "Testing of Optical Pickup Assemblies" for
detailed procedures for determining basic functionality of most of the
optical, electronic, and mechanical components in the pickup assembly.
These techniques do not require sophisticated test equipment and will
identify most common failures.  However, you should not consider such
involved tests until you have eliminated other possibilities for your
particular problems.

Chapter 12) Servo Systems and CD Player Adjustments

  12.1) Servo systems

There are several servo systems in a CD player:

1. Focus - maintains a constant distance to within 1 um (1/25,000th
   of an inch!) or so between the objective lens and the disc.  This
   must be maintained even with a slightly warped or uneven disc and
   in a portable player, with a certain amount of movement as well.
   Focus is accomplished with a voice coil type of positioner (similar
   to operation of a loudspeaker) using optical feedback from the
   disc surface.  See the chapter: "Startup Problems" for a description
   of how this and fine tracking (below) operate.

2. Fine tracking - centers the laser beam on the disc track (to within
   a fraction of a um) and compensates for side-to-side runout of the
   disc and player movement.  This also uses a voice coil positioner
   and optical feedback from the disc surface.  (Note: on rotary
   type pickups, there may be no separate tracking coil as its function
   is combined with the rotary positioner.)

3. Coarse tracking - moves the entire pickup assembly as a function of
   fine tracking error exceeding a threshold or based on user or
   microcontroller requests (like search or skip).  Coarse tracking
   uses several types of positioners depending on performance
   requirements.  It may either be a worm drive, a gear drive, a linear
   motor, or rotary positioner - in order of increasing access speed.

   The linear motor and rotary positioner have no gears and simply use
   a coil and permanent magnet to move the entire pickup very quickly -
   similar to a voice coil but on a larger scale.  CDROMs, especially
   the high performance models, usually use this type of actuator to achieve
   their relatively fast access.  These may have some type of lock to prevent
   the pickup from banging around when the unit is moved with power off.
   Note: for a CDROM drive that uses a caddy - always remove the caddy
   before transporting the drive or the equipment that it is in.  The
   loading of the caddy often unlocks the pickup permitting it to flop around
   during movement and possibly being damaged.

   A linear motor or rotary positioner driven pickup should move very
   smoothly and easily by hand when unpowered and unlocked.

   Note that the use of a rotary positioner is no guarantee of fast response.
   One of the earliest CD players - a Magnavox unit apparently manufactured
   by Philips - has about the slowest track seek time I have ever seen and
   uses a rotary positioner.  Watching it go from one track to another is
   like watching an inch worm crawl along - ssst, ssst, ssst (the sound made
   as the focus actuator vibrates while crossing tracks), ssst, ssst.

4. Spindle speed - maintains constant linear velocity (CLV) of disc
   rotation based on a PLL locking to the clock signal recovered from
   the disc.  Spindle drive is most often done with a permanent magnet
   DC motor connected to the disc platform.  It may be similar to the
   other motors in CD players and VCRs, (as well as toys for that matter),
   or a higher quality brushless DC motor.

  12.2) Play adjustments

You will see a circuit board, hopefully in your unit it is readily accessible
with component markings.  For each servo, there will be 1 or 2 pots to adjust.
Unfortunately for our purposes, some CD players have no adjustments!  In this
case about all you can do is confirm that the lens is clean and clean and
lubricate the mechanism.

The adjustments will be labeled something like:

1.   Focus - F.G. (focus gain), F.O. (focus offset)

2,3. Tracking - T.G. (tracking gain), T.O. (tracking offset), maybe others.

4.   Spindle PLL, PLL adj., Speed, or something like that.

DO NOT TOUCH THE LASER POWER ADJUSTMENT - you can possibly ruin the laser
if you turn it up too high.  Sometimes, just turning it with power applied
can destroy the laser diode due to a noisy potentiometer.  This adjustment
can only be made properly with the service manual.  It may require an optical
power meter to set laser output.  Very often the adjustment is on the optical
pickup itself so it should be easy to avoid.  Sometimes it is on the main PCB.
The laser optical power output is feedback controlled and unlikely to change
unless the laser is defective - in which case adjustments will have little
effect anyway.  If you run out of options, see the section: "Laser power adjustment" - last.

DO NOT JUST GO AND TWEAK WILDLY. You will never be able to get back
to a point where the disc will even be recognized (without test equipment
and probably a service manual).

First, somehow mark the EXACT positions of each control.  Some of these
may require quite precise setting - a 1/16 of a turn could be critical,
especially for the offset adjustments.

Sometimes, there will be marked test points, but even then the exact procedure
is probably model dependent.

  12.3) Adjustment procedure for noise or skipping

The assumption here is that you can get the disc to play but there is
audio noise skipping, or other similar problem.

Play a disc at the track that sounds the worst - put it into repeat mode
so it will continue for awhile.  Get it to play by whatever means works.

  12.4) Repetitive noise at disc rotation frequency

Try to locate the adjustments for focus.  Try the focus offset
first, just a hair in each direction.  If you go too far, you will loose
focus lock totally, the servo will go into focus search mode and/or
the unit will shut down.  Return the control to the exact
original position if there is no improvement.  You can also try gain,
but in my experience, the gain controls are not critical to
normal play but determine how the unit will handle dirty and/or defective
discs.  However, if they are way off, there could be general problems.
Too low a gain setting (this applies to focus as well as tracking) will
make the unit very prone to skipping as a result of minor bumps.  Too
high a setting will make the unit skip as a result of minor disc defects.

  12.5) Short distance skipping or sticking

Try to locate the adjustments for tracking.  Try the fine tracking offset
first, just a hair in each direction.  If you go too far, you will loose
servo lock totally, the pickup will slew to one end of the disc, and/or
the unit will shut down.  Return the control to the exact
original position if there is no improvement.  Then try the other
tracking offset if there is one and also the gain (though this is probably
not the problem).

Always return each control to its original position after the test so you
don't confuse things more.

  12.6) General servo adjustment procedure

If you have a service manual for your player, by all means follow its
recommendations or at least read through its adjustment procedures before
attempting the one given below.  If you have an oscilloscope of at least
5 MHz bandwidth, using it to monitor the RF testpoint during these adjustments
will be of great value.  However, a scope is not essential.

* Once focus lock is established, there should be a strong signal at the
  RF testpoint - typically around a volt or so.  It may initially appear
  somewhat random, however.

* Once tracking lock is established, this signal should appear similar to
  the 'eye' pattern (see section: "The CD player 'eye' pattern" for details.
  However, while seeking, this may be jumping around somewhat as it attempts
  to home in on the correct track location.

If your CD player has a TEST MODE, see the section: "Pioneer PD/M series servo adjustment procedure" and modify it accordingly.  The following
procedure is for a typical unit without such a test feature.  It assumes
that the unit is functional but internal controls are not in their correct
position.  This might be the case if you violated rule #1 - never wildly
tweak any internal adjustments!  Or, if a major subassembly like the optical
pickup or mainboard has been replaced.

If you have not touched the internal controls and no major parts have been
replaced, there is no need to perform this procedure.  Use techniques and
observations discussed elsewhere in this document.

The following are assumed:

    * Controls on the main board are in an unknown state but not any
      laser power adjustments (hopefully, these were on the optical
      pickup itself or its flex cable and were not touched.

    * The player is otherwise functional - there is no physical damage.

You may need to modify this procedure based on your particular model.  Some
of the adjustments may go by different names or be non-existent.  Use
your judgement.  Except for the laser power adjustment, which should be
avoided, it is unlikely that any settings of these controls will result in
permanent damage.

Some of these adjustment will need to be performed while the unit is
in the startup sequence attempting to read the disc directory.  Until
focus and possibly tracking and CLV lock are established, it may give
up fairly quickly.  You will just need to keep cycling power or opening
and closing the drawer to get it to repeat the attempt.  Once some subset
of the servo adjustments are set within reasonable limits, the player
may continue to spin the disc ad-infinitum.

Hopefully, the adjustments on your player's mainboard are clearly marked.
This is not always the case.  I have restored a totally messed up portable
with totally unmarked controls to a marginal state of happiness using an
incremental procedure while observing changes in behavior and the signal
at the RF testpoint with an oscilloscope.  It was not fun and I never was
able to really make it fully functional - seeks still have a problem though
it will start track 1 most of the time and once started, play is flawless.
(I suspect that there may be actual electronic/optical problems with this
player in addition to the randomly tweaked controls).  I even had to poke
at random (testpoints were marked only with TP numbers) to locate the RF

Use both your eyes and ears.  The following may not apply but are probably
worth considering:

* If the sled slews to one end of the track immediately upon power-on or
  loading of the disc, there may be a coarse tracking balance control that
  is set incorrectly.

* If the disc does not start spinning at all, focus lock is probably not
  being achieved.  Concentrate on the RF and focus adjustments.

* If the disc spins hessitently or in the wrong direction or the sled slews
  to one end of the track after the disc starts spinning, there is a good
  chance that the tracking adjustments need attention.

* If the disc goes into overdrive, check the PLL/VCO/CLV adjustment (whatever
  it is called on your model).

* If the disc starts spinning and continues to spin at the correct speed (500
  to 200 rpm depending on track position) without the player shutting down, a
  valid data-stream is probably being read.  This indicates at least marginal
  RF, focus, tracking, and PLL/VCO/CLV settings.  This doesn't mean  you can
  ignore these adjustments but at least it is progress!

* If the disc directory (TOC) is read successfully but the player has trouble
  locating a track to begin play (even track 1), concentrate on the tracking
  adjustments - focus and PLL/VCO/CLV are probably fine.

If the player works but there are noise or tracking problems and you
have an oscilloscope, see the section: "Diagnosis of erratic play" first
as the simplified procedure described there may be more appropriate.

1.  Precisely mark the current positions of all internal adjustments - just
    in case they were already set correctly!

2.  Set all main board controls to their midpoint.

3.  Adjust TR BAL (Tracking Balance) to the center of the range over
    which the sled remains stationary.  Outside this range, the pickup will
    slew to one end or the other.  Not all CD players have this control.
    A CD may need to be in place for this adjustment to have any effect.
    If you are unable to get the pickup to remain stationary, try fine
    tracking offset (TR.OFF) as well.

The following two items should be done with no disc in place.  If your
player does not have suitable test points or if these controls have no
effect without a disc in place, skip them.

4.  While monitoring the testpoint for focus error (e.g., TP.FE), adjust
    focus offset (FO.OFF) for 0 volts (+/- 10 mV or so).  This may not
    be the optimal setting but will get you in the ballpark.

5.  While monitoring the testpoint for tracking error (e.g., TP.TE), adjust
    fine tracking offset (TR.OFF) for 0 volts (+/- 10 mV or so).  This may not
    be the optimal setting but will get you in the ballpark.

6.  If you have a DMM, VOM, or scope, put it on the Focus OK testpoint if
    there is one.
7.  Load a disc and press PLAY if necessary to initiate the startup sequence.

8.  Confirm that focus is established.  There is an adjustment range for
    Focus Offset over which focus will be reliably achieved.  Outside this

    * The lens will hunt up and down - possibly with clicking sounds as it
      bumps into the end stops.

    * The Focus OK testpoint will not be asserted or will be jumping around
      as well.

    * The disc may never start spinning or spin erratically (model dependent).

    * Single play units will give up and enter stop more with display of
      'disc', 'no disc', 'error', etc.  Changers will come up with similar
      display and then move on to the next position of the carousel or

    Center the focus offset within the range for which focus is stable if
    it was not already there.

At this point there is a fair chance that the disc has started to spin and
even that the disc directory has been displayed.  If not, there are still
two sets of adjustments remaining.

9.  With focus stable, the disc should spin up.  It needs to reach and lock
    at about 500 rpm - roughly 8 revolutions per second.  If it does not move
    or overspeeds, try adjusting the PLL/CLV control (may be called PLL.ADJ,
    VCO.FR, CLV.ADJ, etc.).  Note: this assumes that the spindle motor and
    driver are in good condition.  If there is any doubt, see the section:
    "Testing of motors".)  WARNING: if the disc spindle speed runs away,
    turn power off and wait for spindle to stop completely.  PLL/CLV control
    may be set to high; turn it counterclockwise 1/4 turn and start try again.
    There will be some range of this control where the speed will not run
    away but will be within the required limits.

Now, these is an even better chance that the disc has started to spin and
that the disc directory has been displayed.  If not, there is still one
set of adjustments remaining.

10. Fine tracking offset may still not be quite right.  Try some slight
    adjustments on either side of the current position.  You may have to
    cycle power or open and close the drawer if you go too far.  Some
    adjustments of alternately fine tracking offset and PLL/CLV may be

Hopefully, you now have a disc directory and play may be operations though
perhaps with audio noise and/or skipping or sticking.

The following are best done with a scope monitoring the 'Eye' pattern or
other testpoints but if you do not have one, use your ears.

11. Adjust PLL/CLV control to midpoint of range in which disc plays correctly.
    Test this at both the start and the end of a full length (74 minute) disc.
    The optimal setting will result in the control being centered within the
    range over which the player works reliably at both ends of the disc.

12. Adjust any RF Offset (RF.OFS) control to the midpoint of the range over
    which play continues normally with no audio noise.

13. Set Focus Gain (FO.GAIN or FO.G) to the midpoint of the range over which
    it locks.  CAUTION: the disc may enter a runaway state if you go to far.
    Check at both the beginning and end of the disc.  Focus gain may need to
    be increased if the player is overly sensitive to bumps or disc wobble
    It may need to be decreased if sensitivity to disc defects is too high.

14. Set Tracking Gain (TR.GAIN or TR.G) to the midpoint of range over which it
    locks.  CAUTION: the disc may enter a runaway state if you go to far.
    Check at both the beginning and end of disc.  Tracking gain may need to
    be increased if the player is overly sensitive to bumps or disc wobble.
    It may need to be decreased if sensitivity to disc defects is too high.

15. Press STOP and then PLAY again to confirm that the disc loads properly
    and the directory comes up quickly and the music starts without excessive
    delay, hunting, or hesitation.

16. Test forward and reverse search and seek functions for proper behavior.
    Some slight adjustments to tracking balance or fine tracking offset may
    be needed to equalize the forward and reverse search or seek speed.
17. Player should now operate normally.  However some tweaking of the gain
    controls may be necessary (as described above) for optimum defective disc
    and track seek performance over entire disc.

If you have an oscilloscope capable of at least 5 MHz bandwidth, you can now
optimize the amplitude and stability of the 'eye' pattern at the RF testpoint
by going back and touching up the various offset (RF, focus, fine tracking)
adjustments.  Unless otherwise instructed by the service manual, it is probably
safe to assume that the RF signal should be maximum when everything is properly
adjusted.  For example, if the tracking offset and/or E-F balance is not set
properly, you may find that the RF signal amplitude *decreases* when the
tracking servo is closed since the laser beam is consistently off-center with
respect to the row of pits and lands.  (With the servo loop open, the beam was
crossing tracks more or less at random so it was sometimes centered!)

  12.7) Tips for adjusting CDROM drives

The following assumes that your CDROM driver and MSCDEX load without errors
and that your IRQ, DMA, and any other software settings are correct but that
seeks take a long time to complete or fail and/or data reads are unreliable.

If you can get the CDROM drive to play an audio CD, that can be used to
do an initial alignment.  The procedure below provides a way of monitoring
data read performance while performing final servo adjustments since this is
more critical than audio.  Assuming, of course, that (1) there are any
controls to adjust and (2) that you can get to them with a disc in place!

If after using the procedures described in the section: "General inspection, cleaning, and lubrication", and possibly even servo alignment using an audio
CD, the drive still produces data errors or cannot be read at all, it is time
for more serious testing:

(Portions from: the_tooth_wraith (the_tooth_wraith@ptel.net))

Locate a copy of Disk Detective or another CD-ROM diagnosis program.

I'm pretty sure that Disk Detective (the limited version rather than
professional version) can be downloaded over the internet.  Check Mitsumi's
web site.  I use the limited version that ships with a new Mitsumi IDE drive.
It works perfectly on IDE, Mitsumi, SCSI, and likely any other interface
drives, and it does not require the presence of any Mitsumi drive or
controller.  If you can't find Disk Detective, then search for CD-ROM, CDROM,
or CD ROM at: http://www.shareware.com, and you'll find CD-ROM diagnostic

In Disk Detective, there is a Test Disk menu option that scans the entire
disk, and gives a continuous output to the screen of read errors it
encounters, giving the type of error and the average data throughput.

Now using Disk Detective (or a comparable program), load a disk into the
drive and select the test disk option, and tell it to scan the disk from
beginning to end, and tell it not to stop when it encounters an error.  Disk
Detective should start trying to read the disk at sector zero, and will
display read errors as it encounters them.

You might have to load an audio disk rather than a data disk in order to be
able to get to the Test Disk screen.

With the Test Disk screen displaying the errors as it attempts to read the
drive, it will be possible to carefully tweak each of the servo adjustments
(as described elsewhere in this document) to minimize errors and maximize

  12.8) Low laser power

Indications of reduced laser power include erratic startup, noisy playback.
excessive variation of playback quality depending on the particular disc,
or total lack of startup.

WARNING: improper adjustment of the laser power may result in the absolutely
instant destruction of the laser diode - the heart of your CD player.  There
will be no warning.  One moment you have a working laser diode, the next you
have a DELD - Dark Emitting Laser Diode.  Read the relevant sections fully
before attempting any adjustments.

Nothing will help a dead laser diode - whether as a result of your efforts
or natural causes - short of replacing the optical pickup.

Very likely, low laser power indicates a sick laser as well and adjustments
will have limited if any effect since optical feedback normally maintains
laser diode output at the proper level and it may be doing all that is

However, sometimes due to component drift (this one way of saying: I haven't
got a clue), the power will drop slightly or the sensitivity of the photodiode
array will decrease resulting in a marginal signal.

If you have the service manual and it provides a procedure not requiring
a laser power meter (which you probably do not have), then by all means
follow that procedure.

Otherwise, see the section: "Laser power adjustment" for procedures that
may be used as a last resort.

  12.9) Optical alignment

Unless the unit was dropped, optical realignment of the laser assembly
is not likely to be needed.  All critical components are screwed,
sealed with loctite, or glued, and should not change alignment under
normal use.  Don't fall for the line 'CD players are very delicate
and will need frequent alignment - buy our extended service plan'.  CD
players are remarkably robust.  Portables, even when nibbled on by large
dogs, often survive unscathed.  I even carried a component type CD player
home from a garage sale 5 miles on the back of a 10 speed road bike over city
streets complete with potholes!  No problems.  In fact, it improved. The seller
claimed that it was broken but I could find nothing wrong!  One possible
exception is for automotive units which are subjected constantly to bumps
and vibration which eventually take their toll.

If you really believe that optical alignment is needed, I strongly recommend
that you obtain the service manual.  Special test discs or jigs may be
required and some test equipment will be required.  As with other adjustments,
make sure you can get back to your starting point should the need arise.
Again. eliminate other possibilities first if possible.

Chapter 13) Motors and Spindles

  13.1) Small motors in CD players

Conventional miniature Permanent Magnet (PM) motors are usually used for:

* Drawer/tray opening/closing.

* Spindle rotation.

* Pickup position (coarse tracking) unless the unit uses a linear motor
  or rotary positioner drive.

* Disc changing (changers and jukeboxes only).

* Optical pickup tilt (laserdisc players only).

These are DC motors with commutators and metal brushes and are very similar
in construction and quality to typical motors found in cameras, toys, portable
tools, and other electronic equipment like VCRs and audio cassette decks.

They usually run on anywhere from a fraction of a volt up to 10 or 12
volts DC on-off (e.g., drawer) or from a servo controller (spindle).

Some CD players and CDROM drives use brushless DC motors for spindle
driver rather that the cheap PM brushed variety.  The commutation
circuitry for these may be external to the motor itself.  Troubleshooting
beyond searching for bad connections will probably require a schematic.

Sled movement in high performance CD players and CDROM drives often uses
either a linear or rotary direct drive (voice coil) mechanism.  Since
these are integral parts of the coarse tracking servo system, the only
thing that can be tested without a schematic is for coil continuity.

  13.2) Problems with small PM motors

These motors can fail in a number of ways:

* Open or shorted windings - this may result in a bad spot, excess load on
  the driver, or a totally dead motor. 

* partial short caused by dirt/muck, metal particle, or carbon buildup on
  commutator - this is a common problem with spindle motors which fail to
  reach proper startup speed.

* dry/worn bearings - this may result in a tight or frozen motor or a spindle
  with excessive runout.

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