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


  3.7) For more information on CD technology

The books listed in the section: "Suggested references" include additional
information on the theory and implementation of digital audio, laserdisc,
and optical drive technology.

A Fundamental Introduction to the Compact Disc Player is a somewhat more theoretical discussion of compact disc audio technology with diagrams and even some equations. If it doesn't put you to sleep, you will find quite a bit of interesting information in this article. In either case, it may prove of value. Andy Poggio's relatively short article: From Plastic Pits to "Fantasia" provides a nice overview of CD technology. A site with CD-R specific information including some repair tips is:

  • Rictee's CD-R Page. An extensive amount of information on other optical disc/k technologies with many useful links can be found at:
  • Leopold's LaserDisc Page.
  • The MiniDisc Page.
  • The DVD Page.
  • DVD Central at E/Town.

  • Chapter 4) CD Player Placement, Preventive Maintenance, and CD Care


      4.1) General CD player placement considerations

    Proper care of a CD player does not require much.  Following the
    recommendations below will assure peak performance and long life, and
    minimize repairs.
    * Locate the CD player in a cool location.  While the CD player is not
      a significant heat producer, keeping it cool will reduce wear and
      tear on the internal components and assure a long trouble free life.
    * Don't locate CD players in dusty locations or areas of high (tobacco)
      smoke or cooking grease vapors.  I cannot force you to quit smoking,
      but it is amazing how much disgusting difficult to remove brown grime
      is deposited on sensitive electronic equipment in short order from
      this habit.
    * Make sure all audio connections are tight and secure to minimize
      intermittent or noisy sound.
    * Finally, store CDs away from heat.  The polycarbonate plastic used to
      mold CDs is quite sturdy but high temperatures will eventually take
      their toll.  Return them to their jewel cases or other protective
      container when not being played.

      4.2) Preventive maintenance

    You no doubt have heard that a CD should be cleaned and checked periodically.
    "Purchase our extended warranty" says the salesperson "because CD players
    are very delicate and require periodic alignment".  For the most part, this
    is nonsense.  CD players, despite the astonishing precision of the optical
    pickup are remarkably robust.  Optical alignment is virtually never needed
    for a component CD player and is rarely required even for portable or
    automotive units.  In fact, modern CD players often don't even have any of
    these adjustments - the components of the optical pickup are aligned at the
    factory and then fixed in place with hardening sealer.
    An occasional internal inspection and cleaning is not a bad idea but not
    nearly as important as for a VCR.  Realistically, you are not going to do
    any of this anyway.  So, sit back and enjoy the music but be aware of the
    types of symptoms that would be indications of the need for cleaning or other
    preventive or corrective maintenance - erratic loading, need to convince the
    CD player to cooperate and play a disc, audio noise, skipping, sticking, and
    taking longer than usual to recognize a disc or complete a search.
    If you follow the instructions in the section: "General inspection, cleaning, and lubrication", there is minimal risk to the CD player.  However, don't go
    overboard.  If any belts are in good condition (by appearance and stretch
    test), just clean them or leave them alone.  Except for the Sony drawer
    loading mechanism, belts are rarely as much of a problem in CD players as
    in VCRs.
    Of course, acute symptoms like refusal to play or open the door is a sign
    of the need for emergency treatment.  This still may mean that a thorough
    cleaning is all that is needed.

      4.3) CD lens cleaning discs

    Every CD, stereo equipment, department, discount, store - and even sidewalk
    venders - carries CD lens cleaning discs.  Are they of any value?  Can they
    cause damage?
    I generally don't consider CD lens cleaning discs to be of much value for
    preventive maintenance since they may just move the crud around.  However,
    for pure non-greasy dust (no tobacco smoke and no cooking grease), they
    probably do not hurt and may do a good enough job to put off a proper
    cleaning for a while longer.  However, since there are absolutely no sorts of
    standards for these things, it is possible for a really poorly designed
    cleaning disc to damage the lens.  In addition, if it doesn't look like a CD
    to the optical pickup or disc-in sensor, the lens cleaning disc may not even
    spin.  So, the drawer closes, the drawer opens, and NOTHING has been

      4.4) CD protection and handling

    Although CDs are considerably more tolerant of abuse than LPs, some
    precautions are still needed to assure long life.  Also, despite the
    fact that only one side is played, serious damage to either side can
    cause problems during play or render the CD totally useless.
    It is important that the label side be protected from major scratches which
    could penetrate to the information layer.  Even with the sophisticated
    error correction used on the CD, damage to this layer, especially
    if it runs parallel to the tracks, can make the CD unusable.
    The CD is read by focusing a laser beam through the bottom 1.2 mm of
    polycarbonate.  As a result of the design of the optical system used in the
    pickup, at the bottom surface, the beam diameter is about 1 mm and thus small
    scratches appear out of focus and in many cases are ignored and do not cause
    At the information layer with the pits, the beam diameter has been reduced
    to under 2 um.  Still, scratches running parallel to the tracks are more
    problematic and can cause the optical pickup to get stuck repeating a track,
    jumping forward or back a few seconds, or creating noise or other problems
    on readout.  In severe cases, the CD may be unusable especially if the
    damage is in the directory area.
    This is why the recommended procedure for cleaning a CD is to use soap and
    water (no harsh solvents which may damage the polycarbonate or resin overcoat)
    and clean in a radial direction (center to edge, NOT in the direction of the
    tracks as you would with an LP).  While on the subject of CD care, CDs should
    always be returned to their original container for storage and not left out
    on the counter where they may be scratched.
    If there is a need to put one down for a moment, the label side is probably to
    be preferred since minor scratches have no effect on performance so long as
    they do not penetrate to the storage layer below (in which case the CD is
    probably history).  Protectors are available to prevent damage to the label
    side of the disc.  Personally, I think this is taking care to an excessive
    level but, hey, if you use your CDs as frisbies, go for it!

      4.5) CD cleaning

    You do not need a fancy CD cleaning machine.
    Use a soft cloth, tissue, or paper towel moistened with water and mild
    detergent if needed.  Wipe from center to edge - NOT in a circular motion
    as recommended for an LP.  NEVER use any strong solvents.  Even stubborn
    spots will eventually yield to your persistence.  Washing under running
    water is fine as well.
    Gently dry with a lint free cloth.  Do not rub or use a dry cloth to clean
    as any dirt particles will result in scratches.  Polycarbonate is tough
    but don't expect it to survive everything.  Very fine scratches are not
    usually a problem, but why press your luck?

      4.6) Should I really worry about cleaning my CDs?

    Something that not everyone is aware of is the multilevel error handling
    technology in a CD player.  Therefore, a dirty CD may not produce instantly
    obvious audio problems but can nonetheless result in less than optimal
    audio performance.
    Very severe errors - long bursts - will result in audible degradation
    including noise and/or muting of the sound.  Even this may not always be
    detectable depending on musical context.
    Shorter runs of errors will result in the player interpolating between
    what it thinks are good samples.  This isn't perfect but will probably not
    be detected upon casual listening.
    Errors within the correcting capability of the CIRC code will result in
    perfect reconstruction.
    Not all players implement all possible error handling strategies.
    Therefore, it is quite possible for CD cleaning to result in better
    sound.  However, a CD that is obviously clean will not benefit and
    excessive cleaning or improper cleaning will introduce fine (or not so
    fine) scratches which can eventually cause problems.

      4.7) Can a dirty CD or dirty lens damage my player?

    So the droid in the CD store warned you that dirty CDs could do irepairable
    harm to your CD player, your stereo, your disposition, etc.  "Buy our $19.95
    Super-Laseriffic CD cleaning kit".
    The claim made at one major chain was that dirt or dust on the laser eye would
    cause heat build-up that would burn out the mechanism. This is different
    from a dirty disc. The cleaner he was pushing was a little brush attached to
    a CD that brushed off the lens as it played.
    This is total rubbish.  The power of a CD laser is less than 1 mW and is not
    concentrated at the lens.  And, as noted elsewhere, those cleaning CDs with
    the little brush are next to useless on anything but the smallest amount of
    dry dust.
    There are a lot of suckers out there.  Save your money.
    The worst that can happen is the CD will not play properly.  There may be
    audible noise, it may fail to track properly, abort at random times, or not
    even be recognized.  The electronics will not melt down.
    It is just about impossible for a dirty CD to do any damage to the player.
    A dirty lens will only result in disc recognition or play problems similar
    to those caused by a dirty CD.  The laser will not catch fire.
    The only way damage could occur is if you loaded a cracked CD and the crack
    caught on the lens.
    You do not need any fancy CD cleaners in any case - soap or mild detergent
    and water and a soft cloth are all that are required.  If the CD looks clean,
    it probably will be fine.  If there are serious smudges or fingerprints,
    then cleaning could make a significant difference in performance.
    For further information, see the sections "CD cleaning" and "General inspection, cleaning, and lubrication".

      4.8) Rental or library CD considerations

    Unlike old or worn video tapes, it is unlikely that a 'bad' CD could damage
    your player.  If the borrowed CD is dirty, clean it as described in the
    section: "CD cleaning".  If it is badly scratched, the worst that will happen
    is that it will sound bad - skipping and audible noise.  No damage to your
    player will result.  However, if the CD is cracked or broken (this is really
    difficult to do but I have gotten cracked CDs from public libraries), don't
    even attempt to load it - a broken edge could catch on the lens and ruin
    the optical pickup entirely.

      4.9) Can a CD player damage CDs?

    The perhaps unexpected answer is a definite *yes* even though everyone has
    heard about the virtues of non-contact laser playback.  There are several
    ways that a broken or poorly designed or manufactured player can result in
    scratched discs:
    * If the lens moves too high while attempting to focus and the mechanical
      stop does not prevent it from hitting the disc, scratches can occur.  On
      some players, the objective lens can easily go this high if focus is not
      found on the first pass.  Note that in most cases, the lens will not suffer
      since it is protected by a raised ridge which is what actually scratches
      the disc.
    * Mechanical misalignment of the spindle motor or plastic cabinet parts can
      result in the disc touching the bottom or top of the disc compartment and
      this can leave scratches.  This could be the result of poor or cheap design,
      shoddy manufacturing, or damage from a fall or other abuse.
    * If the control logic gets confused, it may allow you to eject a disc while
      it is still spinning and not fully supported by the spindle platter.  A
      dirty disc that resulted in failure of the CLV servo to lock can result in
      a disc speed runaway condition with some players.  If the drawer is then
      opened too soon, the disc will still be spinning because the controller has
      no way of knowing its present status and will not have provided enough
      reverse torque to stop the spindle motor - or too much and it will be
      spinning in reverse.
    The likelihood of any of these is increased with dirty, smudged, warped, or
    previously damaged discs.
    Minor scratches may not result in a serious problem and there are products
    to polish them - don't know how well they work.  However, if these scratches
    can be proven to be a direct consequence of a defective player still under
    warranty, you should try to get some compensation from the manufacturer for
    any seriously damaged and now unplayable CDs.

      4.10) Repairing a scratched CD

    So your five year old decided that your favorite CD would make nice
    frisbee - didn't really know much about aerodynamics, did he?
    Now it sounds like a poor excuse for a 78 rpm record.  What to do?
    There seem to be about as many ways of fixing scratches on CDs as producing
    them in the first place.  However, they fall into 3 classes of techniques:
    1. Mild abrasives: plastic or furniture polish, Brasso metal polish,
       toothpaste.  These will totally remove minor scratches.
    2. Fillers: turtle wax, car wax, furniture wax.  Apply over the whole disc
       and buff out with a lint free cloth.  Filling larger scratches should
       be fairly effective but the disc will be more prone to damage in the
       future due to the soft wax.
    3. Blowtorch.  At least one person who claims to have worked for several years
       in used CD store swears by this technique. Supposedly, he uses a pencil-type
       pocket butane torch and with great dexterity fuses the surface layer of the
       readout side of the disc so that all of those scratches and unsightly
       blemishes-well-melt away. Obviously, there are dangers in using fire on
       plastic and this is likely a last resort.  I would assume that you are
       rolling with hysterical laughter at this point.  In any case, I would not
       take this approach too seriously :-).
    As with cleaning a CD, when applying or rubbing any of these materials,
    wipe from the center to the outside edge.  A CD player can generally track
    across scratches that are perpendicular to its path reasonable well, but
    not those that run the parallel to the tracks.
    A mild abrasive will actually remove the scratch entirely if it is minor
    enough.  This is probably more effective where the surface has been scuffed
    or abraded rather than deeply scratched.
    Wax-like materials will fill in the space where the scratch is if the
    abrasive was not successful.  Even deep scratches may succumb to this
    A combination of (1) and (2) may be most effective.
    Exorbitantly priced versions of these materials are available specifically
    marketed for repair of CDs.  However, the common abrasives and waxes should
    work about as well.
    I cannot comment on the use of the blowtorch or how many years of practice is
    required to get you CD repair license with this technique.  However, I am
    highly skeptical that this works at all and suspect that destruction of the CD
    is the most likely outcome - totally melting, warping, or cracking or
    shattering from the thermal stress.  In other words, I don't recommend trying
    the Blowtorch approach unless you have a stack of AOL or MSN CD to sacrifice
    and you have sufficient accident insurance!
    An alternative to CD home repair are companies specializing in this service.
    A couple of these are: Aural Tech CD and CD Repairman.  I do not have
    information as to their effectiveness or cost.  However, if you have a very
    special irreplaceable CD that someone used as a skateboard, one of these may
    be worth considering.

      4.11) Repairing top-side problems on CDs

    If scratches penetrate to the information layer, all bets may be off.  Much
    of the optical system compliance with respect to damage depends on the short
    depth of focus assuring that surface scratches *on the bottom* will be out
    of focus and ignored.  This is not possible with damage to the pits.  Even
    though the CIRC code should be able to deal with thousands of bad bits, such
    damage can confuse the tracking servos to the point where the disc will be
    What if the aluminum (or gold) reflective layer has come off with no damage
    to the plastic underneath?  First of all, I don't know how this could occur
    unless you were attempting to clean them with a strong solvent.  Any physical
    damage which removed the mirror coating will also damage the pits and recoating
    will be useless.
    (Note that I have unintentionally removed the gold coating on a CD-R using a
    solvent similar to what is in Liquid Wrench(tm).  I was actually trying to
    remove the label but went a little too far!  The solvent apparently dissolved
    the greenish coating or binding underneath allowing the gold film and label
    to just flake off - very strange behavior.  Most of the green layer was still
    intact.  I now have a nice greenish somewhat transparent plastic coaster.)
    Some discs may still work on some players or drives without the aluminum
    coating.  However, this isn't that likely.  How to replace it?  Ideally,
    vacuum deposition is needed.  The problem isn't only the reflectance but
    the micro structure - the original coating was vacuum deposited to conform
    to the pits and lands of the information layer.  It is perfectly uniform below
    the resolution of the laser beam.  Modeling (silver or gold colored) paint is
    amorphous and rough at these feature sizes and floppy disk write protect
    stickers or other adhesive backed reflective films don't even come close
    to contacting the information layer consistently.  Mirror paint may work
    but is a long-shot.

    Chapter 5) CD Player and CDROM Drive Troubleshooting


      5.1) SAFETY

    While there are far fewer potential dangers involved in servicing a CD player
    compared to a TV, monitor, or microwave oven, some minimal precautions are
    still required when working with the cover removed.  These relate to electrical
    connections to the AC line and exposure to the laser beam:
    * Electrical: There may be a few exposed electrically live parts from the
      power line, usually around the power cord entrance, power transformer,
      and on/off switch.  If there are, tape them over or cover them somehow
      so you need not be concerned with a low tech shock!  Unless you are
      troubleshooting a primary side power supply problem, there will be no
      need to go near the AC line.
    * Laser:  The laser in a CD player is infra red, near IR - 780 nm - border
      of visible range but for all intents and purposes invisible.  However, it
      is very low power (generally under 1 mW at the lens) and due to the optics,
      extremely unlikely that you could be in any danger.  Nonetheless, don't
      go out of your way to look closely into the lens while the unit is on!
      Caution: there is usually a very low intensity (in appearance) emission
      from an IR laser which appears deep red.  It will be visible as a spot the
      size of the period at the end of this sentence when the lens is viewed from
      an oblique angle.  This may be a spurious emission in the red part of the
      spectrum or just your eye's response to the near IR energy of the main beam.
      In either case, do not be mislead into thinking that the laser is weak as a
      result of noticing this.  The main beam is up to 10,000 times more intense
      than it appears!  Take care.  However, the red dot is an indication that the
      laser is being powered and probably functional, though it is no guarantee of
      the later.  You really need a laser power meter or at least an IR detector
      to confirm the existence of an IR laser beam.
      Whenever a full size (5-1/4") CD is in place, there is absolutely no danger
      of exposure to the laser beam.  Reflections of laser light at these power
      levels are harmless.  However, if you are testing with a 3-1/2" 'single' or
      homemade cut-down test CD (see the section: "Useful ways to mangle CDs"),
      avoid staring into the lens if there is any chance the laser is powered.

      5.2) Troubleshooting tips

    Many problems have simple solutions.  Don't immediately assume that
    your problem is some combination of esoteric complex convoluted
    failures.  For a CD player, it may just be a bad belt or dirty lens.
    Try to remember that the problems with the most catastrophic impact on
    operation (a CD player that will not play past track 6) usually have
    the simplest solutions (the gears that move the optical pickup need 
    lubrication).  The kinds of problems that we would like to avoid at all
    costs are the ones that are intermittent or difficult to reproduce: the
    occasional audio noise or skipping or a CD player that refuses to play
    classical CDs (depending on your tastes!) of music composed between the
    years 1840 and 1910.
    When attempting to diagnose problems with a CDROM drive, start by trying
    to get it to play an audio CD.  Data readback is more critical since
    the error correction needs to be perfect.  However, with audio playback
    functional, all of the optical pickup and most of the servo systems and
    front-end electronics must be working.  A CDROM drive which cannot even
    play a music CD will have no chance of loading Windows 95.
    If you get stuck, sleep on it.  Sometimes, just letting the problem
    bounce around in your head will lead to a different more successful
    approach or solution.  Don't work when you are really tired - it is both
    dangerous and mostly non-productive (or possibly destructive).
    Whenever working on precision equipment, make copious notes and diagrams.
    You will be eternally grateful when the time comes to reassemble the unit.
    Most connectors are keyed against incorrect insertion or interchange
    of cables, but not always.  Apparently identical screws may be of differing
    lengths or have slightly different thread types.  Little parts may fit in
    more than one place or orientation.  Etc.  Etc.
    Pill bottles, film canisters, and plastic ice cube trays come in handy for
    sorting and storing screws and other small parts after disassembly.
    Select a work area which is well lighted and where dropped parts can
    be located - not on a deep pile shag rug.  Something like a large plastic
    tray with a slight lip may come in handy as it prevents small parts from
    rolling off of the work table.  The best location will also be relatively
    dust free and allow you to suspend your troubleshooting to eat or sleep or
    think without having to pile everything into a cardboard box for storage.
    Another consideration is ESD - Electro-Static Discharge.  The electronic
    components - especially the laser diode - in CD players, CDROM drives, and
    similar devices, are vulnerable to ESD.  There is no need to go overboard but
    do take reasonable precautions like not wearing clothing made of wool that
    tends to generate static.  When working on component CD and laserdisc players,
    get into the habit of touching a ground like the metal chassis before touching
    any circuit components.  The use of an antistatic wrist strap would be further
    insurance especially if the optical pickup assembly needs to be unplugged for
    any reason.
    A basic set of precision hand tools will be all you need to disassemble
    a CD player and perform most adjustments.  However, these do not need to be
    expensive.  Needed tools include a selection of Philips and straight blade
    screwdrivers, needlenose pliers, wire cutters, tweezers, and dental picks.
    A jeweler's screwdriver set is a must particularly if you are working on
    a portable CD player or CDROM drive.
    For making servo adjustments, non-metallic fine tip jeweler's screwdrivers
    or alignment tools will be essential as some of the front-end circuitry may
    be sensitive to body capacitance - contact with the slot may alter the
    behavior of the player (for better or for worse).  In a pinch, wrapping
    electrical tape around the part of a normal jeweler's that you grasp will
    probably provide enough isolation.  However, with a tool with a blade made
    out of an insulator, you will be less likely to accidentally short things
    out as well
    You should not need any CD specific tools except in the unlikely event you
    get into optical alignment in which case the service manual will detail what
    tools and special rigs are needed.
    A low power fine tip soldering iron and fine rosin core solder will be
    needed if you should need to disconnect any soldered wires (on purpose
    or by accident) or replace soldered components.
    See the document: "Troubleshooting and Repair of Consumer Electronics
    Equipment" for additional info on soldering and rework techniques.
    For thermal or warmup problems, a can of 'cold spray' or 'circuit chiller'
    (they are the same) and a heat gun or blow dryer come in handy to identify
    components whose characteristics may be drifting with temperature.  Using the
    extension tube of the spray can or making a cardboard nozzle for the heat
    gun can provide very precise control of which components you are affecting.
    For info on useful chemicals, adhesives, and lubricants, see "Repair Briefs,
    an Introduction" as well as other documents available at this site.

      5.3) Test equipment

    Don't start with the electronic test equipment, start with some analytical
    thinking.  Many problems associated with consumer electronic equipment
    do not require a schematic (though one may be useful).  The majority
    of problems with CD are mechanical and can be dealt with using nothing
    more than a good set of precision hand tools; some alcohol, degreaser,
    contact cleaner, light oil and grease; and your powers of observation
    (and a little experience).  Your built in senses and that stuff between
    your ears represents the most important test equipment you have.
    A DMM or VOM is necessary for checking of power supply voltages and
    testing of sensors, LEDs, switches, and other small components.  This does
    not need to be expensive but since you will be depending on its readings,
    reliability is important.  Even a relatively inexpensive DMM from Radio
    Shack will be fine for most repair work.
    For servo and other electronic problems, an oscilloscope will be useful.
    However, it does not need to be fancy.  A 10 to 20 MHz dual trace scope
    with a set of 10X probes will be more than adequate for all but the most
    esoteric troubleshooting of CD players and CDROM drives.
    To determine if the laser diode is working properly, a laser power meter is
    very useful.  Such a device is expensive but is often essential to properly
    and safely adjust laser power on many CD players and CDROM drives.  However,
    for many problems, simply knowing that an IR laser beam is being emitted is
    enough.  For this, the simple device described in the section: "IR detector circuit" is more than adequate.  Alternatively, an inexpensive IR detector
    card or even some camcorders can perform the same function. 
    A stereo amplifier and loudspeakers is essential to allow your most important
    piece of audio test equipment to function effectively - your ears.  A lot can
    be determined by listening to the audio output to distinguish among dirt,
    lubrication, servo, control, and other mechanical or electronic problems.
    I would caution against the use of headphones as a sudden burst of noise
    could blow your eardrums and spoil your entire day.
    For testing of optical pickups, some additional equipment will be needed.
    However, this will be detailed in the section: "Testing of Optical Pickup Assemblies".

      5.4) Test CDs

    An inexpensive test CD is nice to have just to be able to play known
    frequencies and volume levels.  However, it is not essential - any
    half decent CD will work just fine for most tests.  For many players,
    even an old CDROM disc will be adequate to diagnose startup problems.
    However, to fully exercise the limits of the player, a disc with a full
    74 minutes of music will be needed - Beethoven's Ninth Symphony is a
    good choice (even if you are not into classical music) since it is usually
    very close (or sometimes slightly over) this length of time.
    Keep those old demo CDs or even obsolete CDROM discs - they can be used
    for testing purposes.  Where an optical deck has a servo problem, the 
    disc will end up spinning out of control.  Stopping this suddenly may
    result is the CD scraping itself against the drawer or or base of the
    deck and getting scratched.  Therefore, some 'garbage' discs are always
    handy for testing purposes.
    To evaluate tracking and error correction performance, any CD can be turned
    into a test CD with multiple width strips of black tape, a felt tip marker,
    or even a hand drill!  In fact, some professional test discs are made in
    exactly this manner.
    Also see the sections: "Comments on test discs" and "Custom test CDs using CD-Rs".

      5.5) Useful ways to mangle CDs

    These suggestions will allow you to put some of those AOL CDs to good use
    (well, besides making high tech coasters)!
    * For portable CD players where the designers in their infinite wisdom put some
      of the servo adjustments *under* the spinning disc, a 3-1/2" CD 'single' is
      extremely handy.  A normal CD can be cut down as well - to whatever size you
      need as long as enough actual tracks are left so that the directory and a few
      minutes of music/data remain - this could be as little as about 2-1/2" to
      gain access to the adjustments on some models.  This surgery is best done on
      a band saw with a narrow fine tooth blade.  However, tiny cracks may grow in
      from the edge (overnight, even) if the disc is subjected to any heating or
      stress from cutting or smoothing.  Perhaps some annealing is needed to
      prevent these from getting started.
      Note that the lower mass (actually the lower moment of inertia for you
      purists) of the small CDs may alter the servo response somewhat.  Putting a
      heavy metal ring or washer on top should help.  However, this is still much
      much better than continually having to remove a normal CD to get at the
      adjustments, incrementally moving them one way or another, and then
      replacing the CD to see how you made out.  One can grow old doing this!  The
      little CDs will enable you to monitor the test points as the adjustments are
      made which is also a definite advantage :-).
      The RCA RP-7903A Portable CD Player is an example of a design where this
      type of modified CD is invaluable for testing.
    * A handy special miniature CD can be made to permit viewing of the focusing
      action on any CD player or CDROM drive as long as you can get to the top of
      the deck while testing.  Using a band saw, cut a garbage disc down so as to
      leave only a 1-1/2" diameter center hub with a 1/2" by 1/2" tab sticking out
      from it.  This can then be positioned by hand to just cover the lens while
      it is supposed to be doing its focus search.
    * An alternative that will permit you to view both the laser output (from a
      safe distance) and the focusing action is to create a window in a garbage CD
      by removing the label and aluminum layers from an area of the CD at the inner
      tracks - at least a square inch worth.  Lacquer thinner (nail polish remover,
      with adequate ventilation) will probably work to remove the label.  Fine
      sand paper or steel wool will remove the aluminum and information pits/lands
      (grooves).  Then polish with a buffing wheel or old rag.
    Caution: when using any of these cut-down or windowed test CDs, or 3-1/2"
    'singles', avoid staring into the lens when the laser is powered.  See the
    section: "SAFETY".

      5.6) Getting inside a CD player or CDROM drive

    WARNING: you will void the warranty, if any.  You may make the problem worse,
    possibly much worse.  If the player partially worked, it may no longer even
    recognize the disc directory.  You may accidentally damage parts that were
    perfectly fine.  If you should decide to then have the unit professionally
    serviced, you may find that the shop simply refuses to touch it if they
    suspect your tampering.  There is nothing worse than having to undo 'fixes'
    introduced by a well intentioned do-it-yourselfer where the state of the
    player is now a total unknown.  At best you will be charged for this effort on
    a time and materials basis.  It may be very costly.  It may not be worth the
    A CD player still under warranty should probably be returned for service for
    any covered problems except those with the most obvious and easy solutions.
    On the other hand, it is possible that you will do a better job than some
    repair shops.  You will probably have a better understanding of the basic
    theory and will certainly be able to spend much more time on the problem.
    And, of course, hobbiest/handyman's time is cheap - as in free.
    * Component CD players.  It is generally very easy to remove the top cover on
      most CD players.  There are usually some very obvious screws on the sides
      and possibly back as well.  These are nearly always Philips head type - use
      the proper screwdriver.  Once all the screws are out, the top cover will
      lift up or slide back and then come off easily.  If it still does not want
      to budge, recheck for screws you may have missed.
      Once the top cover is removed, the optical deck and electronics board will
      usually be readily accessible.
      In rare cases, removing the bottom cover will provide access to the solder
      side of the electronics board.  However, with most CD players, the bottom
      is solid sheet metal and the entire board would need to be unmounted.  On
      some, the electronics board is mounted upside-down so there is full access
      to the wiring side once the cover is removed.
    * With most single play designs, the entire optical deck can be lifted out
      after removing 3 or 4 screws.  One screw may have a grounding contact under
      it.  Replace this in exactly the same position.  There may be fragile
      flexible cables.  Be careful so as not to damage any.  Usually, these cables
      plug in to connectors on the electronics board and permit the entire optical
      deck to be easily replaced if needed (not very common, however, despite what
      you may have heard).
    * For changers, details will depend on the particular model but in general, it
      is more likely that removal of the entire changer mechanism will be more
      involved.  However, this is usually not needed unless there is an actual
      mechanical problem with it.  With Pioneer cartridge changes, for example,
      the optical deck is easily removed with just 4 screws.
    * For portables, the bottom plate or top cover usually comes off after
      removing several very tiny screws - use the proper size Philips blade
      jeweler's screwdriver and don't lose them.  Then, you either have access to
      the bottom of the mainboard or the top of the mainboard blocked mostly by
      the optical deck.  With the RCA RP-7903A Portable CD Player, it is the latter
      and the pickup and/or normal size CD conveniently block all access to servo
      adjustments and test points (which as is often the case, are ummarked in
      this RCA unit).  These types of CD players are usually quite a pain to
      troubleshoot!  Of course, there are also many components including most of
      the large multilegged ICs surface mounted on the *bottom* side of the
      mainboard which makes for even more fun should probing be required!  You can
      easily see all the 'stuff' packed into a box just slightly larger than a CD!
    * For CDROM drives, both top and bottom covers may be removable depending on
      model.  These are more wide open than portables, especially the newer models
      where everything has been shrunk to a tiny optical pickup and circuit board
      with a few large ICs.  Unfortunately, adjustments (if any) and test points
      are even less likely to be labeled on CDROM drives.  All testing will also
      require a working PC unless your model has built-in audio play capability.
    Make notes of screw location and type and immediately store the screws away
    in a pill bottle, film canester, or ice cube tray.
    When reassembling the equipment make sure to route cables and other wiring
    such that they will not get pinched or snagged and possibly broken, or have
    their insulation nicked or pierced, and that they will not get caught in
    moving parts.  Replace any cable ties that were cut or removed during
    disassembly and add additional ones of your own if needed.  Some electrical
    tape may sometimes come in handy to provide insulation insurance as well.
    (This applies mostly to portables and CDROM drives - component CD players
    are very wide open.

      5.7) CD enhancers

    The process of reading a CD is digital.  I have seen and heard advertisements
    for sonic rings or special magic markers to improve the quality of the digital
    audio reproduction.  This is total bunk.  Don't waste your money.  These
    products do nothing beyond depleting your pocketbook - and enhancing those
    of the vendors.
    For more amusement, see the section: "Totally worthless gadgets for CD enthusiasts".
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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]