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Sony SL-810D Beta VCR

Discussion in 'Electronic Repair' started by Chris F., Jul 13, 2011.

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  1. Chris F.

    Chris F. Guest

    I service beta VCR's for resale, and right now I've got a Sony SL-810D
    that's driving me up the wall. When I acquired it, it was totally dead.
    Replacing the STK regulator on the power supply got it going, but the tape
    would only operate in reverse (even when it was supposed to be playing
    normally) and was also going way too fast. I replaced the capstan motor with
    a known-good one, this restored the correct bi-directional function, but the
    speed issue remains. When in normal playback mode, the tape runs at near
    fast-forward speed. When in slow-mo, it runs at just above normal playback
    speed. Pause, fast forward, and rewind work normally. The capstan free speed
    adjust potentiometer does have some effect, but doesn't bring the speed
    anywhere near within range.
    The problem is present both during playback and record, and it correctly
    senses BII or BIII recordings, ruling out any issues with the A/C head or
    associated circuitry. I've spent countless hours pouring over the service
    diagrams, and have swapped numerous IC's from the ST-18 board with
    known-good ones from another VCR, all to no avail. I've also checked all the
    caps in that area for ESR.
    Without a thorough knowledge of VCR design, all I can do at this point is
    swap parts. I thought I had enough skill, but I cannot grasp enough of this
    particular circuit design to effectively troubleshoot the problem. A good
    place to start would be knowing where to find the reference voltage or
    signal that determines the overall capstan speed.
    Can anyone give me any ideas, or better yet, does anyone have another one
    of these units for parts?
     
  2. Does the service manual show waveforms? Try checking those. This might
    narrow down the problem.

    Also, given the unit's presumed age, look for something electrical, rather
    than electronic -- bad board or cable connections.

    By the way, it's pore, not pour.
     
  3. David Farber

    David Farber Guest

    Hi Chris,

    Some basic things to check: Is the pinch roller engaging properly? Is the
    capstan motor actually moving the tape or is it getting some help by perhaps
    a take up motor or clutch that has too much torque? Try and add some drag to
    the pinch roller by squeezing it gently with your fingers. If that doesn't
    slow it down, then the tape is being pulled by the take up motor instead of
    being locked into the speed of the capstan motor. If the capstan motor
    really is turning too fast, you're going to have to figure out the servo
    control system. Or another approach is to just give the circuit boards a
    good visual check. A bad connection or cold solder joint could cause some
    strange things to happen. Does tapping on any of the boards have any effect
    on the speed?

    Good luck.
     
  4. Guest

    Is there actually a market for Beta VCR's? I never would have guessed
    that.
    Dave
     
  5. Roger Blake

    Roger Blake Guest

    I know I still use Beta, have a big library of tapes and a couple of
    working Beta VCRs. Heck, there's still a market for RCA "needlevision"
    CED videodisc:

    http://www.cedmagic.com/selectavision.html

    --
    -----------------------------------------------------------------------------
    Roger Blake (Change "invalid" to "com" for email. Google Groups killfiled.)

    "Climate policy has almost nothing to do anymore with environmental
    protection... the next world climate summit in Cancun is actually
    an economy summit during which the distribution of the world's
    resources will be negotiated." -- Ottmar Edenhofer, IPCC
    -----------------------------------------------------------------------------
     
  6. Chris F.

    Chris F. Guest

    Turns out the capstan motor I subbed was not quite the same, and had a
    different hall effect IC for the FG circuit. I managed to swap the IC from
    the old capstan and that appears to have corrected the problem. Another
    lesson learned......
     
  7. Seen bad tracking potentiometers on some Sony Beta decks - the center tap
    opens up. Cleaning doesn't help, since the tap is actually broken away from
    its holder.
    Some other Sony decks, like the SL-5000 had capacitor issues in the servo
    circuits - there was a kit sold for those.

    Mark Z.
     
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