A friend asked me to fix his CD player deck. This is a bare CD player stereo component. The scratcy noise starts shortly after starting to play, and is fairly constant while playing different CDs, including perfect CDs, no scratches at all. The noise sounds a lot like weak signal AM reception, except without the hiss part of the noise.

I see no burned parts or bulging capacitors. BUT I do see that on the power supply PCB it is a bit heat-discolored under the four diodes in the bridge. WOULD it be worth while to replace the 4 diodes and the big filter capacitor?? Could a weak DC supply be the problem?? Since with no service information I have no clue as to what the supply should be.

The build date is August 1989, so it is not new. I carefully cleaned the laser and sensors, which was the first suspect. No change that I could tell.

So what I am wondering is first, is there a laser power adustment on this CD deck?? And second, has anybody else experienced laser deterioration symptoms like this?? I have no idea as to how much use it has, but it is old. I think that semiconductor lasers do experience intensity loss, and that would certainly explain the weak-signal type of noise.

My guess is that there are no repair parts for that portion of the CD transport assembly, as it is a snap-together transport.
BUT it is not appropriate to tell a friend that "their piece of cheap junk is not repairable."

Has anyone had a better experience with this model?? OR is there a hidden adjustment to increase the laser power just a bit??

Should this post be shown in the "general electronics chat" section also??

 

Given the scratchy nature of the noise, I suspect something in the analog portion of the circuitry, not the digital, perhaps a faulty coupling or filter capacitor.

I would expect a weak digital signal with random errors to give spikes of noise of both large and small amplitude, depending upon which bit(s) in each digital word are corrupted.