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Th-p50x50z, no picture, no screen glow, semi-fine SN board

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    #1

    Th-p50x50z, no picture, no screen glow, semi-fine SN board

    Hi,
    I bought a TH-P50X50 Panasonic plasma TV which had sound but no picture and no error code and no screen glow. The SN board LED was lit green and was humming with no shorts and has the right voltages.
    I thought it was a main board issue so I looked around and managed to pick up the same TV with a cracked screen for cheap, NZ$10.
    I swapped out the main board, no difference.
    Swapped out the PSS board, no difference.
    The TV with the cracked screen had a SN board with a failed buffer IC due to the cracked screen, so i unsoldered it and installed it with the corresponding screen ribbon left unconnected.
    TV fired up fine with a picture on the screen!

    So my thoughts are this:
    I read this post:
    https://www.badcaps.net/forum/showth...ght=c14&page=6
    I figured it could be buffer IC16561 but with no screen glow thought possibly unlikely.
    I figured it could be the IGBT Control chip IC16921?
    I figure the picture data would be coming through but with an un-energized screen it couldn't be seen.
    Service manual for it is below.
    I have parts that can be transferred from one board to another but I'm not sure which parts and would rather not guess as they will be a pain to solder.



    Here's a good picture of it:
    http://assets.shopjimmy.com/media/ca...rhuu-top_3.jpg

    Any help would be appreciated.
    Thanks
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    #2
    Re: Th-p50x50z, no picture, no screen glow, semi-fine SN board

    Did some comparing between the boards and there seems to be an anomaly between the readings of Q16820 between the two boards.
    I'll investigate further.

    Comment

      #3
      Re: Th-p50x50z, no picture, no screen glow, semi-fine SN board

      Made some head way.
      VAD on the working board with the missing buffer IC, the one that has a picture is 100V.
      VAD on the working board that's intact but no picture is 35V.
      I'll do some more investigating.

      Comment

        #4
        Re: Th-p50x50z, no picture, no screen glow, semi-fine SN board

        I think I have figured out the issue but can't figure out why the problem exists.
        The voltages between the two boards are the same when using TPVFG as the earth.
        The problem is that there is a voltage difference between chassis earth and TPVFG.
        Can someone read the service manual to point me in the right direction please?
        TIA

        Comment

          #5
          Re: Th-p50x50z, no picture, no screen glow, semi-fine SN board

          I'm not sure if the voltage difference is because the panel is energized on one and not the other.
          The other thing I noticed was that pin 5, the drain pin of IC16784 (MIP3910), has a fluctuating voltage on the working board of between 180 and 190V and the other board has a steady voltage of about 188V.

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