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    Lg 55ls5700-tb

    All,

    Having an issue with the backlight of a family members Television.

    TV turns on fine and works fine. Around 2hrs into operation the backlights are shutdown. On the power supply board the LED in the board flashes 4 times. Then repeats.

    I have checked all outputs as per service manual and they are spot on. The LED+ GND tes points measures around 76v when operating, but once the backlight drops out it measures 71.3v.

    I originally thought it was a dry solder on the power board, but after replacing with a new board its still playing up. Faulty backlight LEDs?

    Any ideas?

    Thanks.

    #2
    Re: Lg 55ls5700-tb

    Turn down the backlights level in the OSD User menu to as low as you can and see if the backlights will stay on longer.
    Never stop learning
    Basic LCD TV and Monitor troubleshooting guides.
    http://www.badcaps.net/forum/showthr...956#post305956

    Voltage Regulator (LDO) testing:
    http://www.badcaps.net/forum/showthr...999#post300999

    Inverter testing using old CFL:
    http://www.badcaps.net/forum/showthr...er+testing+cfl

    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
    http://s807.photobucket.com/user/budm/library/

    TV Factory reset codes listing:
    http://www.badcaps.net/forum/showthread.php?t=24809

    Comment


      #3
      Re: Lg 55ls5700-tb

      Originally posted by budm View Post
      Turn down the backlights level in the OSD User menu to as low as you can and see if the backlights will stay on longer.
      OK mate. I will give that a go.

      Comment


        #4
        Re: Lg 55ls5700-tb

        OK. So the TV has been running for around 2 1/2 hours with the backlight set to minimum. Every other time it usually switched off the backlights around the 2hr mark. Where from here?

        Comment


          #5
          Re: Lg 55ls5700-tb

          Looking like bad led/s in backlights.
          Last edited by nomoresonys; 01-23-2020, 07:31 AM.

          Comment


            #6
            Re: Lg 55ls5700-tb

            Is there a method to follow to test the backlights?

            Comment


              #7
              Re: Lg 55ls5700-tb

              Please upload the service manual and als the pictures of the whole backside of the TV showing all the board, and straight shot of the whole power supply board.
              Is this the exact board you have?
              https://www.shopjimmy.com/lg-eay6251...led-board.htm#
              Your LED panel has 12 LED strings. Do you have LED tester?
              Try checking each VC_x (LED Cathode return) pin to see if one are more are not the same as the rest. Notes: you need to turn off the dynamic contrast or any settings that will automatically adjust the Backlights zone control or backlights level.
              Never stop learning
              Basic LCD TV and Monitor troubleshooting guides.
              http://www.badcaps.net/forum/showthr...956#post305956

              Voltage Regulator (LDO) testing:
              http://www.badcaps.net/forum/showthr...999#post300999

              Inverter testing using old CFL:
              http://www.badcaps.net/forum/showthr...er+testing+cfl

              Tear down pictures : Hit the ">" Show Albums and stories" on the left side
              http://s807.photobucket.com/user/budm/library/

              TV Factory reset codes listing:
              http://www.badcaps.net/forum/showthread.php?t=24809

              Comment


                #8
                Re: Lg 55ls5700-tb

                OK mate. Will do.

                Comment


                  #9
                  Re: Lg 55ls5700-tb

                  OK

                  Here are the pictures and service manual. No I do not have a led tester. At this stage.
                  Attached Files

                  Comment

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