Lg 55ls5700-tb

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  • UND312DOG
    Senior Member
    • May 2014
    • 63
    • Australia
    #1

    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.
    Tags: None
    • budm
      Badcaps Legend
      • Feb 2010
      • 40746
      • USA
      #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

        • UND312DOG
          Senior Member
          • May 2014
          • 63
          • Australia
          #3
          Re: Lg 55ls5700-tb

          Originally posted by budm
          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

            • UND312DOG
              Senior Member
              • May 2014
              • 63
              • Australia
              #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

                • nomoresonys
                  Badcaps Legend
                  • Jan 2013
                  • 12074
                  • U.S.
                  #5
                  Re: Lg 55ls5700-tb

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

                    Comment

                    • UND312DOG
                      Senior Member
                      • May 2014
                      • 63
                      • Australia
                      #6
                      Re: Lg 55ls5700-tb

                      Is there a method to follow to test the backlights?

                        Comment

                        • budm
                          Badcaps Legend
                          • Feb 2010
                          • 40746
                          • USA
                          #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

                            • UND312DOG
                              Senior Member
                              • May 2014
                              • 63
                              • Australia
                              #8
                              Re: Lg 55ls5700-tb

                              OK mate. Will do.

                                Comment

                                • UND312DOG
                                  Senior Member
                                  • May 2014
                                  • 63
                                  • Australia
                                  #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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