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Sony KV-27S36 HV-to-flyback connector

Discussion in 'Electronic Repair' started by Bob Masta, Sep 10, 2007.

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  1. Bob Masta

    Bob Masta Guest

    I've got an intermittent problem on a 27" Sony TV
    KV-27S36 where the picture "rolls up its eyballs"
    and then goes blank: The bottom of the screen
    goes blank first, and an up-shifted picture shows
    at the top 1/4 or 1/3 of the screen, with scan lines
    becoming coarser toward the bottom of this region
    and then dark below. This situation twitches and
    flickers for several seconds, then all goes dark.
    Cycling power off and back on (after say 10 sec)
    almost always restores the picture, sometimes
    for hours.

    The problem does not always arise on every
    viewing session.

    It does not seem to be particularly temperature
    sensitive, in that spraying "duster" air-in-a-can (which
    can come out quite cold!) on suspect areas seems to have
    zero effect.

    Poking parts with a stick also seems to have no effect
    once the problem starts, but after the problem goes into
    remission (after power cycling), poking at the HV cable
    where it emerges from the flyback brings the problem back.

    Assuming that there is something flaky about that connector,
    I thought I'd just inspect and repair or replace it. But the
    cable only wiggles up and down slightly, and I am uneasy
    about giving it a serious yank. So, is this supposed to come out
    with a yank, or is there some secret? What sort of connector
    is down in the hole?

    Many thanks for any help and advice!










    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!
     
  2. Meat Plow

    Meat Plow Guest

    Does it look like it's designed to come out? And what kind of repair do
    you think you can perform upon it once it's removed? Unless the cable end
    fits into a socket say like an auto distributor there might not be much
    that can be done other than replacing the flyback.
     
  3. JANA

    JANA Guest

    This sounds more like a vertical deflection fault rather than a horizontal
    fault. I have my doubts has anything to do with the flyback, unless it is
    one of the supply voltages from that section.

    Most of the common failures in your model series for this type of fault are
    many of the electrolytic caps and cold solder connections to the output
    devices since they run very hot.

    Use a heat gun and circuit freeze to troubleshoot for the fault. Heat the
    caps in the vertical deflection area, and then test them with an ESR meter.
    You can then use the circuit freeze to test the questionable caps in the
    cold state after you find them to be failing from heat.

    --

    JANA
    _____


    I've got an intermittent problem on a 27" Sony TV
    KV-27S36 where the picture "rolls up its eyballs"
    and then goes blank: The bottom of the screen
    goes blank first, and an up-shifted picture shows
    at the top 1/4 or 1/3 of the screen, with scan lines
    becoming coarser toward the bottom of this region
    and then dark below. This situation twitches and
    flickers for several seconds, then all goes dark.
    Cycling power off and back on (after say 10 sec)
    almost always restores the picture, sometimes
    for hours.

    The problem does not always arise on every
    viewing session.

    It does not seem to be particularly temperature
    sensitive, in that spraying "duster" air-in-a-can (which
    can come out quite cold!) on suspect areas seems to have
    zero effect.

    Poking parts with a stick also seems to have no effect
    once the problem starts, but after the problem goes into
    remission (after power cycling), poking at the HV cable
    where it emerges from the flyback brings the problem back.

    Assuming that there is something flaky about that connector,
    I thought I'd just inspect and repair or replace it. But the
    cable only wiggles up and down slightly, and I am uneasy
    about giving it a serious yank. So, is this supposed to come out
    with a yank, or is there some secret? What sort of connector
    is down in the hole?

    Many thanks for any help and advice!










    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!
     
  4. Bob Masta

    Bob Masta Guest

    Yes, it does look like it's designed to come out... looks exactly
    like an auto distributor socket complete with rubber boot
    that can slide up the cable. Since it seems to be quite
    sensitive to motion, I assumed (hoped!) it was just a flaky
    connection.

    Best regards,


    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!
     
  5. Bob Masta

    Bob Masta Guest

    Thanks for the advice. I will certainly check into these things.
    I agree the problem sounds like vertical deflection, but I am
    trying to work with the fact that I can bring it on by gently poking
    the HV cable at the top of the flyback. Doesn't seem to be
    enough motion to be wiggling the whole flyback and thus
    flexing the circuit board, etc.

    Best regards,


    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!
     
  6. Andy Cuffe

    Andy Cuffe Guest

    Some replacement flybacks require you to reuse the original HV cable.
    On those flybacks, they cable has about 1/4" stripped which is
    inserted in a one way gripper. Once it's in, there's often no way to
    remove it without breaking it. While extracting it from the old
    flyback, the stripped part of the wire often breaks off. The good
    news is that since it doesn't pull out easily, it must be making good
    contact with the gripper. If there was a bad connection there, you
    would see the picture get bigger and dimmer then snap back to the way
    it should be and you would hear arcing coming from the bad connection.

    Have you re-soldered all the bad connections? Those sets often have
    many bad solder connections all over the main board. Be sure to
    re-solder the horizontal drive transformer (off the base of the HOT).
    It often doesn't take much to make a bad solder connection act up.
    The bad connection can be far from the part of the board which seems
    most sensitive.
    Andy Cuffe

     
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