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Sick Gaoo - model PC-29XF20A

Discussion in 'Electronic Repair' started by John, Aug 25, 2003.

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  1. John

    John Guest

    I have a 1992 Panasonic GaooTV - model PC-29XF20A that has developed a
    intermittent thermal problem.

    When first turned on (cold) the TV tuner does not lock (just video and
    audio noise on all channels 2 - 125 (cable network).

    If I immediately switch from the ant input to video 1 (vcr provides
    signal) or video 2 (DVD player) the TV works OK - good video and audio
    from both inputs. Switch back to the ant input and nothing but noise.

    After warm-up the tuner will eventually start working (problem will
    clear - approx 15 minutes - sometimes longer). This is regardless of
    what channel the tuner was left on when the TV was last used.

    Immediately after turn on I can clear the tuner problem by swtiching
    the channel to 13 and then 14 and then back to 13 (tuner locks up -
    problem gone). I discovered this quite by accident but the above
    procedure will clear the problem immediately after power up (unit still
    cold) consistently.

    However, the tuner will sometimes remain functional after using the
    above procedure and sometimes the tuner will fail after a few minutes
    and then come good again once the TV is fully warmed up.

    I realize that the real fix is to try and replace the tuner but on a TV
    this old I wonder first of all if the part would still be available and
    second, if it would be cost effective for me to do so? And, I am not
    positive that the tuner module itself is the culprit. There are some
    potentiometers near the tuner and microprocessor on the main board but
    without a service manual I have not attempted any adjustments.

    The TV does deliver a beautiful picture when it is working and the
    picture tube is showing no signs aging.

    I have inspected and re-worked all the grounds and PCB solder joints
    where the Tuner module (metal can) is attached to the main board but
    with no success.

    This TV has had a history of PCB solder joint defects (mainly in the
    power supply) which I have successfully repaired over the past several
    years.

    Suggestions? Anyone seen this problem before?

    JAH
     
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