Moderator, please make this a sticky. I am tired of repeating this info in multiple posts so I want to make a memory dump in one place.
1. CD won't play:
Observe the mechanism with no disc loaded and the cover off (don't look directly at the lens!) When the player starts, the first thing the micro does is make sure the drawer is loaded and the mechanism has risen up to the play position. Then it will reverse the sled motor until the home position switch closes, then it moves the pickup forward a bit until the switch opens. (If the pickup doesn't move at all, the CD mechanism may not be in the fully loaded position, or there may be a problem with the sled drive or motor. Check the loading belts.) There is a switch that tells the micro that the pickup is in the home position so it can stop the motor and keep the pickup from jamming. If the switch gets dirty the micro keeps the motor on in reverse and the pickup won't move. With no CD in the player, turn the player on and watch the laser pickup (don't look directly at the lens!) If the pickup moves toward the disc motor then moves back, the switch is ok. If the pickup moves toward the disc motor and doesn't move back, the switch is dirty and doesn't close. On Sony based players, the home switch is a leaf switch located on the board that the disc motor is on. There is a plastic cover on the end of the leaf switch. Note what position it is installed in, and gently pull the cover off. Then clean the contacts by drawing 600 grit sandpaper through them just a couple of times. Then flush the debris out with contact cleaner or alcohol and gently replace the plastic cover. Depending on the construction of the mechanism, you may have to remove the disc motor board in order to get to the switch.
After the player correctly senses the home postion, the focus search starts and the laser pickup lens moves up and down. If the lens doesn't move after the pickup finds home, either the pickup is bad or the cable for the pickup is broken, or the drive IC is bad, or there is a power supply problem. Some players have IC protectors that look like transistors with only 2 leads. They go open.
If focus search starts, load a CD. If the disc spins, focus search was successful and the player achieved focus lock. The pickup may be good. If the table of contents is displayed but the player doesn't play, the pickup is either bad or the internal adjustments must be performed. A scope is necessary for this. If you have a scope and can see the RF waveform, it should be 1.2V - 1.5V peak to peak, on a player with a Sony chipset and many others as well. Use a commercially recorded CD, preferably an older issue, because newer issues can have lower reflectivity. If the RF waveform is lower than 1V peak to peak, the pickup is probably bad. Do the adjustments and if the waveform doesn't improve, the pickup is bad. Panasonic / Technics players have lower amplitude on the RF waveform, I think it's 1V peak to peak. Not sure about Philips players, I think they are 1.2 - 1.5V.
If the CD doesn't spin, the pickup could be bad or the disk motor, or disc motor drive could be bad. If the player does focus search and the disc doesn't spin and you hear a sizzling sound, the disk motor is bad. Try giving it a turn with your finger, it may start turning. If you replace the disc motor, the disk table height is critical. Measure the height before you replace the motor. You can use a ruler or calipers or feeler gauges. A good trick is to find something, a piece of wood cut to the same dimension, a nut, several feeler gauges; that fits under the disk table and you can use that as a gig to remount the disk table on the new motor, shoving the table down until it hits your gauge. The disk table must be glued to the motor shaft with a drop of superglue.
2. Skipping CDs:
There are several causes of skipping CDs. The most common is the top bearing of the disk motor is dried up and a couple of drops of light weight machine oil will cure it.
The second most common cause of skipping is the suspension of the CD mechanism is sagging and the CD chuck that holds the CD in place is rubbing on the arm that supports the chuck. This is cured by stretching the springs on the mechanism by the length of one turn. You must be sure to return each spring to the same position on the mechanism, because they are different tensions to account for the weight of the motors. If the player uses rubber bumpers instead of springs you can either replace them, replace them with springs if you can find some, or install washers under the bumpers to bolster them up.
On Sony 5 disc players that are sensitive to vibrations, open the top and insert a CD. Observe the chucking arm and magnetic chuck. On some Sony players the plastic chassis warps over time and the magnet is no longer centered in the chucking arm and rubs against the inside edge of the hole it rides in. If it appears not to be centered, push on the arm, from the front, sides and back to determine which edge the chuck is scraping on. You will be able to hear it scrape. If it does, remove the chucking arm. There is a screw in the back of the arm that adjusts the height of the arm and secures it, along with a spring. Remove the chuck from the arm by twisting the 2 halves until the plastic tabs line up with the openings. Now that the chuck is free, file or cut the hole in the arm on the side that it rubs, to enlarge the hole by about 1/8". Don't overdo it or the chuck will fall through.
Remove all burrs and plastic shavings and re-assemble the chuck and install the arm in the player. Adjust the height of the arm so that the chuck floats in the arm with equal parts above and below the arm. The improper height of the arm is another cause of skipping.
If the chuck is not off center, is it riding too low in the arm and scraping on the arm? If so, adjust the height of the arm if it is adjustable on this model.
Sometimes the machined posts that the laser slides on need to be cleaned and re-lubricated, especially if the owner had pets. Clean them thoroughly with alcohol and then apply 2 drops of light weight machine oil to each post on either side of the laser.
Clean the lens. Use a Q tip moistened with ethanol (NOT Isopropyl alcohol, it can cloud plastic!), distilled water or Kodak Lens Cleaner.
3. Drawer won't open / stay closed:
Replace the loading belts.
This covers most of the problems found in CD players.
