LG 42PG20 - has sound - no picture

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  • r4zorsoft
    Member
    • Feb 2015
    • 11
    • USA

    #1

    LG 42PG20 - has sound - no picture

    Currently I'm troubleshooting an LG 42PG20 plasma television.

    I'm able to confirm that sound works through the three HDMI ports, connected to my PC graphics card.

    I hear a "click" when the TV is plugged in, when it is turned on, and again when the TV is turned off. The red standby light on the front of the TV turns blue when "on".

    At no point does the panel energize/prime - I have blackout curtains in my room, and cannot see any glow whatsoever coming from the panel while testing.

    Initially I assumed the problem was the Y-SUS board (original part number: EBR50221404), so I replaced the board. The new board was indicated to be compatible per the reputable parts vendor (replacement part number: EBR54740702), but replacing the board unfortunately did not resolve the problem.

    The original power board (part number: EAY43533901) provided the following readings on my multimeter:
    • Vs: 3.43V
    • Vs: 3.43V
    • NC: N/A (no pin)
    • GND: 0.00V
    • GND: 0.00V
    • VA: 0.88V
    • VA: 0.88V
    • GND: 0.00V
    • M5V: 0.00V
    • M5V: 0.00V


    Definitely out of spec when compared to the voltage listing from the LG repair manual (see first image attachment). The manual I referenced is located at this documentation PDF

    I installed a new power board (replacement part number: EAY39333001), also different but confirmed to be compatible. Current voltage readings are:
    • Vs: 192.6V
    • Vs: 192.6V
    • NC: N/A (no pin)
    • GND: -1.2V
    • GND: -1.3V
    • VA: 59.6V
    • VA: 59.6V
    • GND: -0.6V
    • M5V: 5.09V
    • M5V: 5.09V


    Despite replacing both the Y-SUS and power boards, there is no change - still have sound, but the panel does not energize/prime.

    The images attached display the replacement boards installed in the TV (parts EBR54740702 and EAY39333001).

    The main board images are included to show:
    • No power
    • Standby
    • Powered on (green light on the left turns off after a few seconds)


    I still have the original boards, and can provide pictures of those if necessary.

    At this point, I am not sure what to do. Kindly advise as to what I should test next.
    Attached Files
  • vicvc
    Member
    • May 2015
    • 13
    • south africa

    #2
    Re: LG 42PG20 - has sound - no picture

    referring to your manual page 20 bottom can you measure vscan(vsc),-vy,zbais and post the values?

    Comment

    • r4zorsoft
      Member
      • Feb 2015
      • 11
      • USA

      #3
      Re: LG 42PG20 - has sound - no picture

      Thanks for your response. My apologies for my late reply. Had to move my things into storage for the past year due to life circumstances.

      I took readings as you suggested:

      vscan: 139.6V
      -vy: 186.8V
      zbias: 81.5V

      Comment

      • ReeceyBurger123
        Never Give Up !
        • May 2014
        • 7325
        • Britain

        #4
        Re: LG 42PG20 - has sound - no picture

        Lol but of a big delay there haha. Hope all is well Also have you tried the test patterns ?
        Please Do Not PM My Page Asking For Help Badcaps Is The Place For Advise, Page Linked For Business Reasons Only. Anyone Doing So Will Be Banned Instantly !

        https://www.facebook.com/Telford-Tel...7894576335359/

        Comment

        • r4zorsoft
          Member
          • Feb 2015
          • 11
          • USA

          #5
          Re: LG 42PG20 - has sound - no picture

          Things are going better, thanks!

          I have not tried the test patterns; the panel does not glow at all in a pitch-dark room. I get the loud relay click when plugging in the power cable and turning it on/off, but there is no light from the panel at all.

          Comment

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