How to Troubleshoot CD-ROM?

Types of problems found in CD playersMany repairs of CD-ROMS can be done without the need for the service manual or the use of sophisticated test equipment, but a reliable multimeter will be needed for any electrical tests and an oscillocope of at least 5 MHz bandwidth is highly desireable for servo alignment and more advanced troubleshooting. The types of problems found in a CD player can be classified into several categories:
A. Mechanical problems such as dirt, lack of lubrication, wear, worn-out rubber parts, dirty switches, or physical damage can all cause failure with CD-ROMS. A dirty lens is probably the cause of the following problems, discs not being recognized, seek failure, audible noise, and erratic tracking, sticking, or skipping. Cleaning of the lens and the turning mirror, and an inspection of the mechnical parts should be the first things done for any of these problems
B. Electrical Adjustments; coarse tracking, fine tracking, focus, laser power. However, some CD players no longer have some of these adjustments. The servo systems are totally digital.
C. Power problems such as lack of 12volt or 5 volt input, or failure of the power supply can be repaired.
D. Bad connections such as broken solder on the pins of components that are stressed like limit or interlock switches, or audio or power jacks, internal connectors that need to be cleaned and reseated, broken traces on flexible cables, or circuit board damage due to a fall all can cause failures of CD-ROMS.
E. Electrical Component Failure such as a power surge or a lightning strike may damage components in the power supply.
You can often repair a CD player which is faulty due to Mechnical failure except for laser power which I would not attempt except as a last resort without a service manual and/or proper instrumentation if needed as improper adjustment can ruin the laser. If discs are recognized at all or even if the unit only focuses correctly, then laser power is probably ok. While the laser diodes can and do fail, don't assume that every CD player problem is laser related. In fact, only a small percentage are due to a failure of the laser diode or its supporting circuitry. Mechanical problems such as dirt and lubrication are most common followed by the need for electrical (servo) adjustments
The solutions to power or bad connection problems are obvious, but it may take a conscious effort to remember to check these out before assuming that the fault is due to something much more serious. Failures in the power supply of CD-ROM can also be repaired fairly easily.
Most other electrical failures will be difficult to locate without the service manual, test equipment, and a detailed understanding and familiarity with CD technology. However, you might get lucky.I have heard of successfully repairing problems like a seek failure, by replaceing a driver chip because it was running excessively hot, or a door sensor failure, where the circuitry was traced to locate a bad logic chip. Since so much of the intelligence of a CD-ROM player is in the firmware, or the program code inside the microcontroller, even the schematic may be of only marginal value.

Troubleshooting Guide

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

Problem: CD-ROM is totally dead.
Possible causes:

1. bad DC voltage connector from power supply.
2. Bad connections or faulty component in power supply or blown fuse.
3. Defective microcontroller.

Problem: CD-ROM is operational but there is no display or partial display.
Possible causes:

1. Burned out back-light bulb.
2. Bad connections to display panel (totally dead or erratic).
3. Bad solder connections on display panel.
4. Bad power supply.

Problem: CD-ROM ignores you.
Possible causes:

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

Problem: Drawer does not open or close.
Possible causes:

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

Problem: Drawer operation is erratic.
Possible causes:

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

Problem: Drawer does not close (or open) completely.
Possible causes:

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

Problem: Spindle table loose or sticks to clamper upon eject.
Possible causes:

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

Problem: Intermittent or erratic operation.
Possible causes:

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

Problem: CDROM drive overheats.
Possible causes:

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

Problem: Operation is poor or erratic when cold:
Possible causes:

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

Problem: Disc is not recognized displaying 'disc', 'error', etc.
Possible causes:

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

Problem: Disc spins in wrong direction or overspeeds and is never recognized.
Possible causes.

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

Problem: Pickup attempts to reset past inner track.
Possible causes:

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

Problem: Seek operations take too long or fail to complete.
Possible causes:

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

Problem: Search, seek, or play starts correctly, then loses time or position.
Possible causes:

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

Problem: Short distance skipping.
Possible causes:

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

Problem: Playback gets stuck (rapid repeat).
Possible causes:

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

Problem: Occasional long distance skipping or repeating.
Possible causes:

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

Problem: Player gets stuck at approximately same time on multiple discs.
Possible causes:

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

Problem: Various tracking problems on portions of discs:
Possible causes:

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

Problem: Repetitive noise at disc rotation rate.
Possible causes:

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

Problem: Audio muting, noise, or distortion.
Possible causes:

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

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. Cleaning the objective lens and turning mirror 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. A CD lens cleaning disc is nearly worthless except for the most minor dust as it will not completely remove grease, grime. 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, I reccommend isopropyl alcohol. You cannot generally get to the bottom surface of the lens but this isn't nearly as exposed as the top surface so it usually isn't a problem.
Do NOT use strong solvents or anything with abrasives - you will destroy the lens surface rendering the entire expensive pickup worthless. Inspect the lens.When clean, the lens should be perfectly shiny with a blue tinge uniform over the central surface.

Turning Mirror

Cleaning the turning mirror is nearly as important as cleaning the lens. 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. 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. For focus the lens should move up and down without sticking. 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. 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.

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. 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, 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. 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. Sometimes the bottom panel of the unit will need to be removed.

Drawer mechanism

Check for free movement. Test the belt for life, it should be firm, reasonably tight, and should return to its original length instantly if stretched by 25% or so. If the belt fails, it will need to be replaced eventually, though a thorough cleaning of the belt and pulleys with isopropyl alcohol or soap and water may give it a temporary reprieve. Also, check the gears and motor for lubrication and damage and correct as necessary. Clean and lubricate 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 the belt, worm gear, other gears, slide bearings. These should all move freely. Inspect for damage to any of these components which might impede free movement. Repair or replace as appropriate. Clean and lubricate with just a dab of high quality light grease suitable for electronic mechanisms such as MolyLube or Silicone grease. A drop of light oil in the motor bearings may cure a noisy or dry bearing. Try to play a disc again before proceeding further.

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! 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 type mode selectors. Never use oil or grease on electrical contacts.