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Sony MHC-695 - cd player problems

Discussion in 'Electronic Repair' started by [email protected], Sep 29, 2005.

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  1. Guest

    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
     
  2. Arfa Daily

    Arfa Daily Guest

    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
     
  3. Guest

    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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