LG 43LJ594V main board not providing stby power

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  • edugimeno
    Badcaps Veteran
    • May 2017
    • 568
    • Spain
    #1

    LG 43LJ594V main board not providing stby power

    I there!
    I have this TV set that doesn't even light up the st by led. I fully checked the PS board and this one is fine, it provides 8.9V when Stdby and 13V when ON (forces by DRV_ON pin according to service document)

    So I checked the main board and it is not able to even light up the stdby led and of course it won't obbey to ON button or remote signals

    I checked all caps on board, none of them is shorted. I took some voltages at those caps, some of them have 8.9v on one side, some don't have any voltage. I see some coils and smalls IC's near banks of SMD capacitors that look like DC-DC converters, there got to be at least one source for 5V and probably some others too (3.3v...), but I can't find any other voltage other than 8,7 across the whole board. My guess is that some DC-DC is not working, but I don't know which one.

    I also tested all cap banks with a ESR tester but the results were inconsistent, probably because some of them need to be tested out of the circuit.

    I checked all diodes and Q's for shortcircuits and they were all good. All DC-DC coils show ~0 Ohms too

    Also the issue is not in another board (TCON...) because I've tried all this with no other cable other than PS and IR board attached.

    I'm attaching a close up view of this main board to see if anyone can suggest any idea on where to look at now


    Thank in advance!
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    • edugimeno
      Badcaps Veteran
      • May 2017
      • 568
      • Spain
      #2
      Re: LG 43LJ594V main board not providing stby power

      Also let me add that the 8.9V has a little "noise", it jumps up&down just a little bit, not 100% stable, probably 0.1 or 0.2v but to me this leads me to think there's some short in the main board? Does this make sense?

      Thanks

        Comment

        • edugimeno
          Badcaps Veteran
          • May 2017
          • 568
          • Spain
          #3
          Re: LG 43LJ594V main board not providing stby power

          I checked the coils. They all test infinite to gnd but the one on the top (L2310) shows 100 ohm to ground...

            Comment

            • edugimeno
              Badcaps Veteran
              • May 2017
              • 568
              • Spain
              #4
              Re: LG 43LJ594V main board not providing stby power

              TV has been fixed, there was a fried choke very close to the socket from PS board, in the +13V line, that was feeding a shorted to GND capacitor.

              All good now, thanks everyone

                Comment

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