CD player repair tips

I don't consider myself an expert on any kind of repair, but I've had more experience with CD players than any other devices. A lot of people have told me that I've inspired them to repair their own players, which is fantastic - so if you're looking to repair your own unit, here are some pointers that might help you. There are literally hundreds of potential issues for CD players and I can't cover them all here, so this is just intended as a starter guide for the more common ones.

Tray won't open

This is by far the most common fault with vintage players and is usually caused by a bad tray belt, but not always. Some players use gears rather than belts, and those can get jammed up by old grease that goes sticky over time. Belts often get stretched or distorted, or just lose their grip. Having a bag of replacements in various sizes will be very useful here. It's also possible that the button has failed and the player isn't getting the message that you want to open the tray. This isn't very common, but worth considering if all else fails.

Skipping issues

Most players use sled rails that the optical pickup slides along. If the original grease on these rails goes sticky over time, it can cause skipping. But any kind of obstruction to the pickup's smooth movement can cause issues. Is the transport lock still on, or partially on? This is usually a lever or nylon screw on the base of the player that prevents the pickup from moving during transport. Are the cables that connect the pickup to the PCB getting snagged on something? Is there some other mechanical obstruction? I recently had a player that was skipping because the main disc motor wasn't spinning freely, so oiling the bearings of motors can make a difference. Also make sure it's not just disc damage - some players are more sensitive to scratches on the disc surface than others, so just because the disc plays perfectly on another machine doesn't mean it's free from blame. Try a perfect disc and see if the problem is still there.

Make sure the pickup lens is clean - this is the easiest CD player maintenance you can do, and might make the difference. The laser needs a clean 'view' to read the data on the disc and will struggle if the lens has a coating of dust or grease.

Sometimes a quick tweak of the tracking adjustment potentiometer is all that's required, but this should be done with caution. Always mark the position of the potentiometer before you start so that your adjustment can be reversed if necessary.

Some vintage players can't play discs that are more than 74 minutes long, since that was the maximum possible at the time they were manufactured. So if your player only skips at the 75 minute mark, there's likely nothing you can do about it.

Disc can't be read/won't spin up

These are often the worst problems, but sometimes it's not as bad as it seems. Some players have a mechanism that lifts the pickup and disc turntable into place rather than dropping the disc down onto it, and these require a strong loading tray belt. So even if your tray belt is strong enough to open and close the tray, it might not have that final 'push' to lift up the pickup. If this is the case, the disc won't even spin up. Try a slightly smaller, tighter belt. Some players are fussy about the exact belt size but you can usually check by turning the loading gear by hand to see if it's going as far as it needs to.

If you're sure it's not a belt issue and the disc still isn't spinning up, make sure the lens of the pickup is clean. To be honest I've rarely seen this kind of fault cured by just cleaning the lens, but it's certainly possible. And when I say clean it, I mean clean it properly - use at least 91% isopropyl alcohol with a cotton swab and gently clean it for several seconds. A quick wipe usually isn't enough. If the lens is particularly dusty, you might have to clean it for 30 seconds.

In order to read a disc, the lens must be in its 'home' position. It reads the disc from the centre and moves to the outside edge, so it starts as close to the disc turntable as it can get. I had a player recently that had a physical obstruction that was stopping the pickup getting to its home position, so it never had a chance of reading discs. Also make sure the limit switches are clean and conducting properly - there is a specific sequence that the player goes through before it will spin up the disc, and that includes getting signals from the limit switches. There will be one for the tray and usually one for the pickup. Use a multimeter on continuity mode to check that the switches are closing properly.

In almost all cases, a disc will only spin up if the pickup achieves focus on the surface of the disc. Occasionally the turntable that the disc sits on will slip down the motor shaft and cause problems. It has to be at a very specific distance from the pickup. Try rotating the disc by hand after it loads. If it's scuffing or otherwise not rotating freely, that's a sign that something isn't right. Is that puck that holds the disc down able to rotate properly? If it's jammed, that's likely to be your problem.

You may just have a weak laser, or no laser output at all. The laser is infrared, so you can't really see it with your naked eye and it's also dangerous to look at. Open the camera app on your smartphone and look at the lens via the screen when you close the tray. If you can see a laser emission and the lens moves up and down to focus, there is hope - but if nothing happens at all you may have a dead pickup or a problem elsewhere in the player. Make sure the cables are seated properly.

If you can find the service manual for your player, and you have the right equipment, you can try carrying out the adjustments for focus and tracking which might have drifted (or been tampered with my someone else). Don't be tempted to adjust the laser power - this really is a last resort, and I've never personally had any success in doing this. But if you must adjust potentiometers, always mark their positions before you start so that you can return them to the original settings if it doesn't work. It's very likely that they are already in the right place, and if you mess with that and can't get them back to where they were, you'll have very little chance of success.

No power

Always check the obvious things first - is the power cord damaged? Measure the AC voltage entering the transformer (using one hand only if you can) to make sure power is at least getting to that point. Also make sure the power switch is working correctly.

If those things are okay but the unit won't turn on, you almost certainly have a blown circuit protector or fusible resistor. These components are there to protect the player in the event of a power surge or short circuit. Circuit protectors are little components that look like transistors, but only have two legs instead of three. If you have the service manual, they will usually be marked with exclamation points on the schematic diagram to indicate that they are critical to the power supply. Fusible resistors are low value resistors (usually between 1 and 3 Ohms) that are designed to fail open in the event of a problem. They are often green in colour and stand off the PCB. They can be replaced by regular resistors, but you will lose their protective value and risk damage to the rest of the circuit.

Before replacing circuit protectors or fusible resistors, try to establish why they blew in the first place. Measure the resistance across the two pads of the fuse - if the reading is low, it indicates a shorted component. Often it will be an electrolytic capacitor, so check them carefully. And if you find one, that's great - but check the others anyway in case there are more.

Disc spinning too fast/backwards

This is probably due to failed electrolytic capacitors. Having an ESR meter or LCR tweezers really helps here because sometimes a capacitor will appear to be fine but have very high ESR (equivalent series resistance) that prevents the circuit working correctly. A visual inspection isn't enough here - occasionally you will see evidence of damage on the PCB, but 95% of the time a failed capacitor looks perfectly normal. I've never once seen a 'bulging' capacitor in a CD player.

Unresponsive buttons

Almost all CD players use momentary tactile switches for the front panel controls. Over time, these can develop oxidation that prevents good contact. They can be replaced quite easily, but the ones you buy in bulk these days usually have a different feel to them - they are more 'clicky' and don't feel as nice to use. My preference is to service the existing ones, which works best if you use a fibreglass pencil. Use a sharp blade to cut off the four plastic 'welds' in the corners, remove the metal plate and plastic button insert, then take out the brass dome. They're easy to lose, so take care. On the underside (concave) side of the dome, use the fibreglass pencil to remove all the oxidation which will probably look black in colour. Be thorough and ensure the dome is shiny. Use the pencil again in the recess of the switch until the small metal contacts are clean and shiny. You might want to use some isopropyl alcohol on a swab to clean this part also. When everything is clean, reassemble the button and use a soldering iron to carefully melt the four corners again to secure the metal plate. You should have just enough plastic material to do this. With luck, your button should work perfectly again.

Optical pickup replacement

With vintage players, this usually isn't even an option. Many use pickups that are now obsolete and almost impossible to find at reasonable prices. However, if you're lucky enough to have a player that uses a Sony KSS-150 or KSS-210, you're in luck - these are interchangeable and can still be purchased relatively cheaply. But a new pickup is rarely just a 'drop in' replacement - carrying out the service manual adjustments after installation is recommended to get the best out of it.

There are plenty of less common issues that you might come across, but the above covers the basics. Although CD players are precision devices, my general experience is that they are surprisingly resilient. The odds are in your favour, so good luck!

Further resources:
There is an excellent, no-nonsense web page with advice on all manner of CD player problems here.

You might also care to try a book called Troubleshooting and Repairing Compact Disc Players by Homer L. Davidson. It's out of print now but you can find copies on eBay or perhaps your local library. It was written in the 1990s so the advice doesn't tend to focus on issues of age, but it might still be helpful to you.