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LG 43UM7100PLB has power, BL and works but with no video

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    #1

    LG 43UM7100PLB has power, BL and works but with no video

    Hi there! Today I got this TV set . It has stdby_led, responds to remote and internally powers on, backlight powers up and all seems to be OK internally but there's no video signal at all ( I don't mean a "No signal" banner, I mean a black screen)

    I opened it and visually found nothing clearly burnt. LVDS cables from main to LCD bars were ok, tried to reseat them but nothing changed

    But I measured voltage on LCD bars (split t-con boards) and going to all capacitors near the lvds cable showed 0.0v. On both sides T-con's. (check attached pictures)

    Is it common that all voltage regulators on both (independent) t-con boards have gone bad at the same time? Should I trace this back to the main board? Any hint on what to try next?

    Thanks!
    Attached Files
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    #2
    Re: LG 43UM7100PLB has power, BL and works but with no video

    Might not work but try a basic reset, unplug tv for a few minutes, hold power button in on tv for 30 seconds if it has one, then plug tv back in and try it.

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      #3
      Re: LG 43UM7100PLB has power, BL and works but with no video

      do you have the audio optic out put lit red???

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        #4
        Re: LG 43UM7100PLB has power, BL and works but with no video

        Can try checking some mainboard voltages, example there, not english but gives the jist: https://www.youtube.com/watch?v=Ab6gMedtAwY

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          #5
          Re: LG 43UM7100PLB has power, BL and works but with no video

          More there, if you get strange readings maybe recheck with the ribbon cables from mainboard to panel unhooked on mainboard side: https://www.youtube.com/watch?v=Aes6WiG2044

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            #6
            Re: LG 43UM7100PLB has power, BL and works but with no video

            Ok, thanks everyone for your comments but...TV is fixed!!
            And the method to fix it was amazing....Guided by one video I found on youtube. I wouldn't have believed it if I hadn't a TV to try it.
            Ok so I used the normal procedure to determine the source of the issue.
            I removed the right hand LVDS cable and the LH t-con board still had no voltages
            I removed the LH LVDS cable and the RH had correct voltages in their main capacitors (17v, 8,7v, 1.8v). So there was an issue in the LH tcon board
            I checked all SMD capacitor I was able to find in that board but I wasn't able to find one that was shorted.
            Then following directions in one weird video I found, I used scotch tape to cover 13 traces starting from trace 4, couting from the right side of the LVDS cable. I reseated this LVDS cable into the TCON and the LCD is working perfectly (both half sides, with no difference in luminosity, etc)
            I understand this is very strange and there has to be a reason for those signals Im not isolating, but the fact is that this TV is now working thanks to 1 centimeter of scotch tape....

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              #7
              Re: LG 43UM7100PLB has power, BL and works but with no video

              This just means your panel is somehow shorted. It can go out in a day, or it can last another 5 years. You will definitely find out lol

              Comment

                #8
                Re: LG 43UM7100PLB has power, BL and works but with no video

                Yes, after watching this guy's video:
                https://www.youtube.com/watch?v=SbGAkRgaZhs
                I understood that the horizontal lines are run across the whole screen from side to side, driven from each side from each LVDS cable, so if the LH row trace is shorted, you can mask it out and leave the power coming from only the RH driver side. This may get a little dimmer but really unnoticeable

                Like you said, time will tell how long this works

                Thanks

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                  #9
                  Re: LG 43UM7100PLB has power, BL and works but with no video

                  There's probably at least 100 videos covering the tape method on youtube.

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