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Panasonic tv doesn't have picture

Discussion in 'Electronic Repair' started by info, Jun 12, 2006.

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  1. info

    info Guest

    My tv has stopped working. The symptoms are as follows,

    Recently I noticed that the picture requires ever longer times
    to start after switching the tv on. The sound comes on
    immediately. I new that eventually, the pictures will not come
    on, and now I have reached that point. It seems as though
    the picture cannot "complete" the "warm up" stage. The
    screen is completely dark, i.e. as if there is no power.
    I have checked all the controls, and it is not a brightness
    setting or the tv/vcr switch, I am sure of that.

    The model is Panasonic TX-W28R3

    I am guessing that this is due to some dried out electrolyte,
    but this is just my educated guess, due to the fact that the
    fault became progressively worse, which could be an
    electrolyte in the process of drying up.

    If anyone has any experience with this particular model, please
    tell me what is the part, and I will fix this in a flash.

  2. Dave D

    Dave D Guest

    It may be something to do with the CRT heater supply, which could indeed be
    due to bad electrolytic caps, or bad solder joints, especially on the CRT
    I take it you are skilled in electronics and are aware of the potential
    lethal dangers within a CRT TV? First things first- check the neck of the
    CRT glows. If it does, the set will need some skilled diagnostics to get any
    further. If it doesn't, the fault should be easy to find as there are few
    parts to go wrong in the heater supply on most sets. Usually it will be a
    bad solder joint or broken PCB track.

  3. info

    info Guest

    I know about the dangers (I have a diploma in EE).
    When you say it may be a bad solder/track, this does not explain
    why the problem got progressively worse. A bad solder/track usually
    causes an intermittant problem?
  4. Dave D

    Dave D Guest

    Yes but a CRT heater has a lot of 'thermal inertia' and takes a good few
    seconds to go from off to on, on to off. A bad connection can often become a
    good one once parts warm up and expansion sets in. With ageing, thermal
    expansion and contraction and some arcing, a worsening connection can be
    fully expected.

    However, I agree the most likely cause is thermally sensitive components,
    especially electrolytic capacitors.

  5. Papa_J

    Papa_J Guest

    Dave: Use your ESR Meter and check the associated electrolytic, having the
    EE Diploma will definitely assist it the rest of the quandary. Cheers.
    FWIW Panasonic and Sony have been known for multiple 'ring cracks' in their
    soldering, esp after a few months of thermal changes during nominal
    operations, it's probable a good illuminated inspection mag lens will
  6. Dave D

    Dave D Guest

    Thanks, but I'm not asking the question, 'info' is the OP!

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