LG 55LS4600 powers on with backlight no image

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  • woodman45
    Senior Member
    • Aug 2015
    • 87
    • U.S.A

    #1

    LG 55LS4600 powers on with backlight no image

    LG 55Ls4600 as title says,powers on back lights are on no image.
    Are there any tests I can do?
    Is the main video board possibly bad?
    Also to mention there is sound just no video.
    Attached Files
  • diif
    Badcaps Legend
    • Feb 2014
    • 6978
    • England

    #2
    Re: LG 55LS4600 powers on with backlight no image

    There's a fuse on the tcon to check, measure for 12v each side of it.

    Comment

    • woodman45
      Senior Member
      • Aug 2015
      • 87
      • U.S.A

      #3
      Re: LG 55LS4600 powers on with backlight no image

      Where is the fuse at on the tcon board
      Attached Files

      Comment

      • nomoresonys
        Badcaps Legend
        • Jan 2013
        • 12086
        • U.S.

        #4
        Re: LG 55LS4600 powers on with backlight no image

        Fuse is labeled F1 2A/125v, black negative probe on chassis/metal ground. red positive probe on each side of fuse.
        Last edited by nomoresonys; 12-21-2019, 06:15 PM.

        Comment

        • woodman45
          Senior Member
          • Aug 2015
          • 87
          • U.S.A

          #5
          Re: LG 55LS4600 powers on with backlight no image

          Originally posted by diif
          There's a fuse on the tcon to check, measure for 12v each side of it.
          Yes 12v on each side.

          Comment

          • woodman45
            Senior Member
            • Aug 2015
            • 87
            • U.S.A

            #6
            Re: LG 55LS4600 powers on with backlight no image

            Originally posted by nomoresonys
            Fuse is labeled F1 2A/125v, black negative probe on chassis/metal ground. red positive probe on each side of fuse.
            Thanks. Yes 12v on both sides.

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA

              #7
              Re: LG 55LS4600 powers on with backlight no image

              What do you get on the screen if you have only one cable between T-CON and LCD panel connected one at a time?
              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

              • yokoono
                Badcaps Veteran
                • Apr 2010
                • 475

                #8
                Re: LG 55LS4600 powers on with backlight no image

                Measure the voltages circled in red and post the values found.
                Attached Files
                Last edited by yokoono; 12-22-2019, 02:17 AM.

                Comment

                • woodman45
                  Senior Member
                  • Aug 2015
                  • 87
                  • U.S.A

                  #9
                  Re: LG 55LS4600 powers on with backlight no image

                  Originally posted by budm
                  What do you get on the screen if you have only one cable between T-CON and LCD panel connected one at a time?
                  Left connector in pic did nothing,right connector unplugged showed half screen.
                  Attached Files

                  Comment

                  • woodman45
                    Senior Member
                    • Aug 2015
                    • 87
                    • U.S.A

                    #10
                    Re: LG 55LS4600 powers on with backlight no image

                    Originally posted by yokoono
                    Measure the voltages circled in red and post the values found.
                    The reading on vcc18 is 1.8
                    Vgl reading is -6.91
                    Vgh reading is 0.00
                    Vod reading is 0.19

                    Comment

                    • yokoono
                      Badcaps Veteran
                      • Apr 2010
                      • 475

                      #11
                      Re: LG 55LS4600 powers on with backlight no image

                      You have problems with the part where there is no image. Connect the defective part and measure the resistance at the VGH point. You can compare with the good side.
                      L.E.
                      It's a short on the VGH rail. You can leave the good side coupled and measure VGH. It can be a short or resistive smd cond, a diode or, worse, the panel.
                      Last edited by yokoono; 12-22-2019, 11:27 AM.

                      Comment

                      • woodman45
                        Senior Member
                        • Aug 2015
                        • 87
                        • U.S.A

                        #12
                        Re: LG 55LS4600 powers on with backlight no image

                        Originally posted by yokoono
                        You have problems with the part where there is no image. Connect the defective part and measure the resistance at the VGH point. You can compare with the good side.
                        L.E.
                        It's a short on the VGH rail. You can leave the good side coupled and measure VGH. It can be a short or resistive smd cond, a diode or, worse, the panel.
                        Those readings are with both sides connected.
                        I found a tcon board for $20, I think I'm gonna get it and if I get the same results is it safe to say the panel has a short?

                        Comment

                        • budm
                          Badcaps Legend
                          • Feb 2010
                          • 40746
                          • USA

                          #13
                          Re: LG 55LS4600 powers on with backlight no image

                          It can be as simple as shorted out caps on the tab bonding board of the bad side.
                          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

                          • woodman45
                            Senior Member
                            • Aug 2015
                            • 87
                            • U.S.A

                            #14
                            Re: LG 55LS4600 powers on with backlight no image

                            Originally posted by budm
                            It can be as simple as shorted out caps on the tab bonding board of the bad side.
                            Should I get the tcon first?

                            Comment

                            • budm
                              Badcaps Legend
                              • Feb 2010
                              • 40746
                              • USA

                              #15
                              Re: LG 55LS4600 powers on with backlight no image

                              I would start checking the caps first, you do want to damage T-CON board if you have shorts circuit on the tab bonding board.
                              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

                              • woodman45
                                Senior Member
                                • Aug 2015
                                • 87
                                • U.S.A

                                #16
                                Re: LG 55LS4600 powers on with backlight no image

                                Originally posted by budm
                                I would start checking the caps first, you do want to damage T-CON board if you have shorts circuit on the tab bonding board.
                                Thanks budm. Which caps should I check on the tab bonding board?
                                I have searched on internet but I can't find much info.
                                Any insight is greatly appreciated.

                                Comment

                                • budm
                                  Badcaps Legend
                                  • Feb 2010
                                  • 40746
                                  • USA

                                  #17
                                  Re: LG 55LS4600 powers on with backlight no image

                                  All the SMD caps on the tab bonding boards, you need to check for very low resistance reading.
                                  You do know what the tab boding boards are, correct? You need to remove the LCD frame to get to the tab bonding board.
                                  Attached Files
                                  Last edited by budm; 12-22-2019, 09:13 PM.
                                  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

                                  • woodman45
                                    Senior Member
                                    • Aug 2015
                                    • 87
                                    • U.S.A

                                    #18
                                    Re: LG 55LS4600 powers on with backlight no image

                                    Originally posted by budm
                                    All the SMD caps on the tab bonding boards, you need to check for very low resistance reading.
                                    You do know what the tab boding boards are, correct? You need to remove the LCD frame to get to the tab bonding board.
                                    I'm assuming the tab bonding board is the board on the bottom that connects into the panel.
                                    With SMD caps how do you read the resistance?

                                    Comment

                                    • budm
                                      Badcaps Legend
                                      • Feb 2010
                                      • 40746
                                      • USA

                                      #19
                                      Re: LG 55LS4600 powers on with backlight no image

                                      No power to TV, set meter to Ohm mode, 200 Ohm scale, then just check the resistance between the two legs of each cap.
                                      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

                                      • woodman45
                                        Senior Member
                                        • Aug 2015
                                        • 87
                                        • U.S.A

                                        #20
                                        Re: LG 55LS4600 powers on with backlight no image

                                        Originally posted by budm
                                        No power to TV, set meter to Ohm mode, 200 Ohm scale, then just check the resistance between the two legs of each cap.
                                        Thanks again budm. I found a video of a guy with similar problem and it was a smd cap on the panel driver board.he shows how to get to it and do the tests.
                                        I will get back and report my findings.

                                        Comment

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