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 Disc Players and CDROM Drives

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انتقل الى الصفحة : الصفحة السابقة  1, 2
كاتب الموضوعرسالة
أحمد جمال
عضو جديد
عضو جديد


عدد المساهمات : 34
تاريخ التسجيل : 16/06/2010

مُساهمةموضوع: رد: Disc Players and CDROM Drives    الأحد يوليو 25, 2010 1:26 am

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.
    However, a few models do permit removal and replacement of the entire
    objective lens assembly without realignment. In such a case, you can get to
    the bottom of the lens as well as additional optics surfaces (see below) for
    cleaning.
    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:
      [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]
    • 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
      position.

    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 (if
    used) 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. Some models may use other types of drawer mechanisms
    but similar recommendations apply.
    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.
    If the there is evidence of dirty or hardened grease, clean the gears and
    track thoroughly as this may interfere with free movement. Use a sharpened
    toothpick or (very carefully) a pin or other tool to get in between each of
    the gear teeth as well to be sure that it is not hard and caked there as
    this may result in erratic operation and skipping.
    Then 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:
    [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط].

Try to play a disc again before proceeding further. I guess you have
already done this.
الرجوع الى أعلى الصفحة اذهب الى الأسفل
أحمد جمال
عضو جديد
عضو جديد


عدد المساهمات : 34
تاريخ التسجيل : 16/06/2010

مُساهمةموضوع: رد: Disc Players and CDROM Drives    الأحد يوليو 25, 2010 1:27 am

Cleaning the inside of the optical pickup



Except under extreme circumstances (like dropping the CD player in the
bathtub), the interior of the optical pickup should remain relatively clean
and dust-free. However, what happens if you DO drop the CD player in the
bathtub? Well, there will no doubt be other problems to deal with but once
those are taken care of (if ever), that leaves the optical pickup.
For many, the turning mirror is accessible by gently lifting up on the lens
assembly after removing the protective shroud. But, even this may not be
possible for some models. And, cleaning all of the other optics may be
difficult or impossible.
For example, on many Sony models, there is a metal plate fastened with a
single screw underneath the pickup. This plate can be removed without
disturbing any adjustments revealing the angled beam splitter and diffraction
grating (of the three beam pickup) in the barrel attached to the laser diode.
These can be cleaned with a Q-tip and alcohol.
However, there is no way to get beyond this point. So, if any water got in
there, the only chance of success would be via an alcohol? soak. Forget
about further disassembly - realignment would be totally impossible without
the factory jigs. A replacement pickup will probably be needed.
Each manufacturer has their own way of assembling a pickup. The only way to
determine if access is possible will be by careful exploration!

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!
الرجوع الى أعلى الصفحة اذهب الى الأسفل
أحمد جمال
عضو جديد
عضو جديد


عدد المساهمات : 34
تاريخ التسجيل : 16/06/2010

مُساهمةموضوع: رد: Disc Players and CDROM Drives    الأحد يوليو 25, 2010 1:28 am

Back to [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط].
General System Problems


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: Audio Equipment and Other
Miscellaneous Stuff for more info on linear power supplies. See
the document Small Switchmode Power Supplies
for more info on DC-DC convertors.

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
problem.
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
display 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.

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
    connectors.
  • 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
proceed further if the problem is not with a bad power supply or bad
connections.

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 like a gear
loose on the motor shaft or a slipping rubber wheel. Such a gear is probably
split and a replacement will be needed. Rubber parts may be cleaned for a
temporary repair but 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".
Another slight possibility is that the player has gotten into a "Dealer
Antitheft" mode which prevents people from stealing CDs or DVDs from demo
units in a store. Consult your user manual or ask the place where
you bought it for the key sequence. to reset it.

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.
الرجوع الى أعلى الصفحة اذهب الى الأسفل
 
Disc Players and CDROM Drives
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