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cd player skipping

Houas07tc

Houas07tc

Well-Known Member
I have a technics 60+1 file cd changer. Most of the time it works great until you start changing tracks and disc, it would start skipping. Is this a simple problem to repair such as replacing the laser eye or should I just chuck it and get a new one. Any suggestion is greatly appreciated.
 
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I had a Mission DAD7000 player that did this. Changing (and realigning)the laser head solved the problem. :D
 
Easier yet, to determine if you need a new laser. Clean the laser FIRST! Pull the unit apart(take the top off should do you) and look at the printed circuit board and look for a pot labeled "tracking" or "gain" or both. This is the laser power output. When the laser gets older, it grows dimmer, Just put in a disc and start playing a track, then turn the pot in one direction or another, until skipping is heard. Turn the pot in the other direction until it stops with just a hair over. Just have just increased the laser output. No guarntee how long it will last. The pot could have a wear spot in it and the voltage lowered due to an incursion at the point where the center spot was stopped on the resistive coating of the pot. Hope this helps...
 
A small correction here. A pot labeled "tracking," "TG," or similar has nothing to do with laser power. It changes the gain of the tracking servo, which can drift or become out of alignment for a number of reasons (including low laser power). It's safe to turn that pot. If TG is low, you will have trouble. As gain increases, noise from the head will increase- that's how you will know which direction you need to go.

Tracking gain is a compromise. Too much gain decreases performance on defects and errors, and can make for audible noise or oscillation from the head. Too little gain makes the player prone to skipping with shock, sonic vibration or marginal discs.

Tracking gain is also not the same as tracking offset and E/F balance. Don't ever touch pots labeled that without an alignment procedure from the service manual in your hand.

Laser power is another story. Most players have the adjustment on the head itself, though some early players do have LP adjustments on the main board. Turning that power pot is tempting complete disaster. Sometimes those pots get dirty, and moving them a half of a degree will be enough to destroy the laser diode. And just a smidge of extra power can be enough to degrade a laser diode very rapidly. One needs a laser power meter to get that correct, if adjustment is indeed in order.
 
PacificStereo said:
A small correction here. A pot labeled "tracking," "TG," or similar has nothing to do with laser power. It changes the gain of the tracking servo, which can drift or become out of alignment for a number of reasons (including low laser power). It's safe to turn that pot. If TG is low, you will have trouble. As gain increases, noise from the head will increase- that's how you will know which direction you need to go.

Tracking gain is a compromise. Too much gain decreases performance on defects and errors, and can make for audible noise or oscillation from the head. Too little gain makes the player prone to skipping with shock, sonic vibration or marginal discs.

Tracking gain is also not the same as tracking offset and E/F balance. Don't ever touch pots labeled that without an alignment procedure from the service manual in your hand.

Laser power is another story. Most players have the adjustment on the head itself, though some early players do have LP adjustments on the main board. Turning that power pot is tempting complete disaster. Sometimes those pots get dirty, and moving them a half of a degree will be enough to destroy the laser diode. And just a smidge of extra power can be enough to degrade a laser diode very rapidly. One needs a laser power meter to get that correct, if adjustment is indeed in order.
Click to expand...

Well, you saved me a job. Good someone was paying attention!
Actually there are some mechanical hangups that are more often the cause of skipping in CD players, these should be checked first.
1. Put a drop of light weight machine oil on the top bearing of the disc motor. Often these bearings dry up causing skipping.
2. If the laser slides back and forth on polished posts, and is not driven by a motor with gears, but instead is driven by a linear motor, clean the posts meticulously with alcohol, then put a few drops of lightweight machine oil on the posts. The gear driven type is less sensitive to grunge on the posts.
 
Ditto the "baptism" of the spindle motor--but do it to both upper and lower brgs. That is in the past my experience of cause of skip far and beyond optics issues. If a drop or two of oil corrects the problem it is temporary, and a new spindle motor is indicated.
 
Old1625 said:
If a drop or two of oil corrects the problem it is temporary, and a new spindle motor is indicated.
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That has not been my experience. A drop of oil will take you through another year at least. Then another drop will take you another year.
 
Another "trick of the trade" for older players:

I just did a PD-5010 today that had a skipping problem caused by the clamp assembly. Most modern clamps are magnetic. Many older ones use pressure to clamp a disc. These can wear and cause issues. Often the top half of the clamp will contain a ball bearing that rests against a flat bushing made of Delrin or some other hard, slippery plastic.

The bushing will develop a divot that wants to capture the ball bearing. The ball bearing will often develop a flat spot. These conditions will interact to cause intermittent skipping.

You want to remove the divot from the bushing, and push the ball bearing out and reinsert it to move the contact spot to some other part of the ball. In the case of Pioneer players that use this arrangement, you can push the bushing out of the "flapper" and lightly sand it on a flat (glass is good) surface (I use 600 grit, then 1500 grit) until the divot is gone. On Yamahas, the bushing is part of a larger part. You have to remove the part from the flapper (two screws), and then carefully sand away the divot.

I like to use a bit of Molykote yellow on the ball before I reassemble these, but you don't have to. Use only a TINY bit if you do this. Too much grease makes for viscosity trouble and may also cause skipping.
 
dr*audio said:
That has not been my experience. A drop of oil will take you through another year at least. Then another drop will take you another year.
Click to expand...

It depends on how long the spindle motor brgs have been starving for lubrication. We cheap Yankees can certainly be culpable on such count.

Sled brgs and such are also suspect, and most of us have wood fires to heat our houses. Lots of dust. Meaning all brgs and the optic lens assy are likely to need attention.

The only other advice I can give is that the player being attended is worth the time.
 
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