Lg 32lb5700 no power on led

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  • axon18
    New Member
    • May 2020
    • 7
    • Portugal

    #1

    Lg 32lb5700 no power on led

    Good Morning,
    I have a TV that suddenly stopped showing pictures. After searching in the internet, i find that could be the LED tapes. I opened the TV and it really had a burnt and scorched tape led ... i replaces them all.
    When I connected everything is the same.
    Can you help me?

    I attach the photos and measurements on and off.

    Sorry my bad english.
    Attached Files
  • dick_barton
    Badcaps Legend
    • Aug 2015
    • 6642
    • Wales

    #2
    Re: Lg 32lb5700 no power on led

    You are missing a signal from the mainboard to turn the leds on. DRV_On should be approximately 3.5V
    Disconnect the mainboard from the power supply and connect a 1K resistor from 3.5V to PWR_On and a second 1K resistor from 3.5V to DRV_ON
    Last edited by dick_barton; 05-27-2020, 04:48 AM.
    Willing to help but I'm no expert.

    Comment

    • salarsat
      New Member
      • May 2020
      • 1
      • iran

      #3
      Re: Lg 32lb5700 no power on led

      Hello
      your board need to be reball CPU !!!!
      do not tuch any thing !!!

      Comment

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

        #4
        Re: Lg 32lb5700 no power on led

        Originally posted by salarsat
        Hello
        your board need to be reball CPU !!!!
        do not tuch any thing !!!
        That's just a HUGE assumption.

        Comment

        • axon18
          New Member
          • May 2020
          • 7
          • Portugal

          #5
          Re: Lg 32lb5700 no power on led

          Originally posted by dick_barton
          You are missing a signal from the mainboard to turn the leds on. DRV_On should be approximately 3.5V
          Disconnect the mainboard from the power supply and connect a 1K resistor from 3.5V to PWR_On and a second 1K resistor from 3.5V to DRV_ON
          Hello, i make what you said and the led poweer on, then i disconnectt the led and check 142vdc in led connector.

          Comment

          • dick_barton
            Badcaps Legend
            • Aug 2015
            • 6642
            • Wales

            #6
            Re: Lg 32lb5700 no power on led

            So the backlight works when you tested using the resistors, yes?
            Willing to help but I'm no expert.

            Comment

            • axon18
              New Member
              • May 2020
              • 7
              • Portugal

              #7
              Re: Lg 32lb5700 no power on led

              Yes

              Comment

              • dick_barton
                Badcaps Legend
                • Aug 2015
                • 6642
                • Wales

                #8
                Re: Lg 32lb5700 no power on led

                It looks like you have a mainboard problem not providing the signal and your leds are OK.

                Can you follow the DRV_ON pin on the mainboard and see if it connects to a transistor/mosfet.
                Willing to help but I'm no expert.

                Comment

                • yokoono
                  Badcaps Veteran
                  • Apr 2010
                  • 476

                  #9
                  Re: Lg 32lb5700 no power on led

                  Or reflow to the processor.

                  Comment

                  • axon18
                    New Member
                    • May 2020
                    • 7
                    • Portugal

                    #10
                    Re: Lg 32lb5700 no power on led

                    Originally posted by dick_barton
                    It looks like you have a mainboard problem not providing the signal and your leds are OK.

                    Can you follow the DRV_ON pin on the mainboard and see if it connects to a transistor/mosfet.
                    After search i find that c701 is missing, there is olny the place with solder.
                    I attatch picure with the pin DRV_ON and the component that is missing.
                    And i don't know what is...i search the board but i can't find the manual..eax65610905
                    Attached Files

                    Comment

                    • dick_barton
                      Badcaps Legend
                      • Aug 2015
                      • 6642
                      • Wales

                      #11
                      Re: Lg 32lb5700 no power on led

                      Why would the smd capacitor C701 be missing? It does look as though it is. Was this TV working for you or do you have it for repair? Has the mainboard been replaced or worked on?
                      Attached Files
                      Willing to help but I'm no expert.

                      Comment

                      • axon18
                        New Member
                        • May 2020
                        • 7
                        • Portugal

                        #12
                        Re: Lg 32lb5700 no power on led

                        The television was working. It was on a living room sideboard and then I posted it on the wall. after that it worked a few hours.
                        It wasn't to fix. It won't pay off. Appliances are very expensive to repair here.
                        Can you tell me what componet i have tu buy tu put there.. to see if works.
                        Regards

                        Comment

                        • dick_barton
                          Badcaps Legend
                          • Aug 2015
                          • 6642
                          • Wales

                          #13
                          Re: Lg 32lb5700 no power on led

                          Unfortunately, I do not know what the component is.
                          Perhaps someone with an identical board could tell you but there would be no guarantee that that is the only problem. There also appears to be an smd resistor alongside that is not in circuit so it may be that they were never included in this version of the mainboard.
                          Last edited by dick_barton; 05-29-2020, 05:50 AM.
                          Willing to help but I'm no expert.

                          Comment

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

                            #14
                            Re: Lg 32lb5700 no power on led

                            That's where a MLLC capacitor would go, see all the others, look around tho, maybe this setup did not require that cap, there are many more places on that board that don't have those caps in place, see them, just because there's a place for one does not mean it was needed in this particular setup/configuration.
                            Last edited by nomoresonys; 05-29-2020, 05:56 AM.

                            Comment

                            • diif
                              Badcaps Legend
                              • Feb 2014
                              • 6978
                              • England

                              #15
                              Re: Lg 32lb5700 no power on led

                              Originally posted by axon18
                              After search i find that c701 is missing, there is olny the place with solder.
                              I attatch picure with the pin DRV_ON and the component that is missing.
                              And i don't know what is...i search the board but i can't find the manual..eax65610905
                              That's definitely looks broken off, non filled pads have more rounded solder domes. I have an identical board here and have just pulled that capacitor, it's 10uf.

                              Comment

                              • dick_barton
                                Badcaps Legend
                                • Aug 2015
                                • 6642
                                • Wales

                                #16
                                Re: Lg 32lb5700 no power on led

                                Originally posted by diif
                                That's definitely looks broken off, non filled pads have more rounded solder domes. I have an identical board here and have just pulled that capacitor, it's 10uf.
                                There's also an smd resistor in the photo I posted that I could not see on his original photo. Is it on your board and can you see its value.
                                Attached Files
                                Last edited by dick_barton; 05-29-2020, 07:48 AM.
                                Willing to help but I'm no expert.

                                Comment

                                • diif
                                  Badcaps Legend
                                  • Feb 2014
                                  • 6978
                                  • England

                                  #17
                                  Re: Lg 32lb5700 no power on led

                                  It's tiny and black which is why it doesn't look like it's there. It's in circuit with the two black devices either side of it, it sits lower than them so it's very unlikely it could be knocked off, unlike that cap.

                                  Comment

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

                                    #18
                                    Re: Lg 32lb5700 no power on led

                                    Yep, looks like it fell off or was removed, what's the tv history? another pic. there: https://www.ebay.com/itm/LG-32LB570V...-/273575219348
                                    Last edited by nomoresonys; 05-29-2020, 12:35 PM.

                                    Comment

                                    • axon18
                                      New Member
                                      • May 2020
                                      • 7
                                      • Portugal

                                      #19
                                      Re: Lg 32lb5700 no power on led

                                      Good evening,
                                      Thank you all for your help. I ended up buying a new card.

                                      Comment

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

                                        #20
                                        Re: Lg 32lb5700 no power on led

                                        Ok, let us know if it works.

                                        Comment

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