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LG Plasma TV with no picture fault finding

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    LG Plasma TV with no picture fault finding

    Hi friends,
    This is my first post in this forum and I hope I would fetch some of your valuable time

    Let me brief, long story short..
    I am working on an LG plasma TV model 42PQ30R.
    The fault is no display.
    The tv is turning on, the blue led is working, however there is no standby (red light), tv automatically going in run mode (i.e blue led)
    Note: sometimes gets off automatically but it happened only once or twice.

    I began my troubleshooting with the power supply, all fuse ok.
    power supply ok, getting the required panel voltages (Vs and Va) at power supply outputs.

    My next step was to check the Ysus board.
    Ysus P201 to SMPS P812 connector is OK.
    Ysus P209 to left X drive --ok
    checked the MOSFETs, IGBTs, all ok except a few, IRGP 4086, IRFP 4332, K3667 (2), but cannot confirm as they were tested onboard, not standalone.
    Ysus P206 to Z sus ---doubtful, reason -fluctuating voltage received at Er com and VS pins which should be as per panel label i.e 94.9 and 193 V respectively.

    My question is what seems to be the fault , am I going in the right direction, what should be my next step?

    additional info- the fault started with the TV displaying coloured snow in picture and then it went pitch black.
    I am taking help from the LG training manual.

    Regards!!

    #2
    Re: LG Plasma TV with no picture fault finding

    Perform a logic board self test, unplug LVDS and power supply cable from main board and short 2 pads on the logic board named EXT_AUTO_GEN, the TV should come on and display test patterns. Without main board plugged the TV powers itself on, then if it runs fine, there is your problem, if not, you need to measure VSUS, VA, VSCN, -VY, ZBIAS and see if they match the panel sticker.

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      #3
      Re: LG Plasma TV with no picture fault finding

      Hi
      I have this issue
      Please help
      Thanks

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