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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Sony MHC-695 - cd player problems
Hello all,
Amidst other junk, I received a Sony HMC-695, which is an integrated mini stereo system. The three-disc cd changer wasn't working at all, always said "no disc" and didn't even try to spin up. I'm told it developed this problem suddenly. It seems that the cd player is contained on a small board beneath the turntable, and the motherboard just sends it commands and receives audio from it. The pickup has an octagonal black shield which is held in place by clips. I forgot to note the pickup model, but it looked a lot like this: http://repairfaq.ece.drexel.edu/sam/kss361a.gif (it did have the letter B in its type though). Cleaning the lens helped a bit: focus locks, disc spins up a bit and the pickup tries its best to move past the inner track. There are three adjustments on the board, which I've guessed to be focus, tracking balance and (tracking?) gain. Adjusting tracking balance (quite a bit from where it was originally), I was able to get the pickup to stay still, but there's still no tracking and no TOC. I just hear the wibbly-wobbly servo noise that Pioneers make with only focus and CLV servos enabled. The disc appears to spin at about the right speed, though it varies a bit. While I was playing around with the adjustments, I got the TOC a couple of times and once it even sort of played (didn't have speakers connected, but the eq-like display had its bars moving up and down). I must've hit the wrong place with my screwdriver. So. Something must have failed in the tracking circuit, but what? Or could the optics just be dirty? The behaviour seemed the same on pressed and CD-R discs, so I don't really think so. I can't figure it out and it's too late at night anyway... br, Ilkka |
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wrote in message ups.com... Hello all, Amidst other junk, I received a Sony HMC-695, which is an integrated mini stereo system. The three-disc cd changer wasn't working at all, always said "no disc" and didn't even try to spin up. I'm told it developed this problem suddenly. It seems that the cd player is contained on a small board beneath the turntable, and the motherboard just sends it commands and receives audio from it. The pickup has an octagonal black shield which is held in place by clips. I forgot to note the pickup model, but it looked a lot like this: http://repairfaq.ece.drexel.edu/sam/kss361a.gif (it did have the letter B in its type though). Cleaning the lens helped a bit: focus locks, disc spins up a bit and the pickup tries its best to move past the inner track. There are three adjustments on the board, which I've guessed to be focus, tracking balance and (tracking?) gain. Adjusting tracking balance (quite a bit from where it was originally), I was able to get the pickup to stay still, but there's still no tracking and no TOC. I just hear the wibbly-wobbly servo noise that Pioneers make with only focus and CLV servos enabled. The disc appears to spin at about the right speed, though it varies a bit. While I was playing around with the adjustments, I got the TOC a couple of times and once it even sort of played (didn't have speakers connected, but the eq-like display had its bars moving up and down). I must've hit the wrong place with my screwdriver. So. Something must have failed in the tracking circuit, but what? Or could the optics just be dirty? The behaviour seemed the same on pressed and CD-R discs, so I don't really think so. I can't figure it out and it's too late at night anyway... br, Ilkka Most likely bet is the pickup itself, however, many of the Sony CD signal processor boards, ( usually called the " BD " board ) mounted under the deck and soldered directly to the spindle and sled motors, have a number of very small surface mount electrolytics, with 3 all side by side along one edge ( the left edge looking from the front, with the deck the right way up ) It's very common for these three to give trouble, and erratic or no servo operation is the typical symptom. Occasionally, they get as far as leaking, and that's where your troubles really start, as the electrolyte attacks nearby thru' plated holes. When replacing them, you must only use similarly specced surface mount types. Conventional minature wire ended electrolytics, just don't work in this particular circuit - trust me ... Hope this helps Arfa |
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Sony MHC-695 - cd player problems
Replacing the caps had no effect, but replacing the pickup fixed it.
The player works flawlessly now. Thanks a bunch. BR, Ilkka |
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