LG Won't turn on 47ld450

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  • Ice203
    Senior Member
    • May 2015
    • 99
    • Uk

    #1

    LG Won't turn on 47ld450

    I have an lg that won't turn on.
    The red standby lights on and when I press the on button the light dims
    Nothing else happens.
    I've replaced all the caps.
    It has the 3.3v and when power button is pressed the power/on pin jumps to 3v the straight back to 0v.
    Also tested rectifier. Diode. Resistors. And regulators. All seem fine.
    If I jump 3.3v to the pwr pin I get the 12v on the other pins



  • tom66
    EVs Rule
    • Apr 2011
    • 32560
    • UK

    #2
    Re: LG Won't turn on 47ld450

    It has the 3.3v and when power button is pressed the power/on pin jumps to 3v the straight back to 0v.
    This is a clue.

    What do the power board outputs do when this happens?

    How long does it jump up for...?

    Main board is a common fault on these sets.
    Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
    For service manual, schematic, boardview (board view), datasheet, cad - use our search.

    Comment

    • Ice203
      Senior Member
      • May 2015
      • 99
      • Uk

      #3
      Re: LG Won't turn on 47ld450

      Thxs for the reply Tom.
      The power pin only keeps voltage for a fraction on a second.
      Same with the outputs. They just to near the voltages but drop straight away.

      Comment

      • tom66
        EVs Rule
        • Apr 2011
        • 32560
        • UK

        #4
        Re: LG Won't turn on 47ld450

        So... would it seem to you that the power board is working... esp since it works when jumped?
        Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
        For service manual, schematic, boardview (board view), datasheet, cad - use our search.

        Comment

        • Ice203
          Senior Member
          • May 2015
          • 99
          • Uk

          #5
          Re: LG Won't turn on 47ld450

          Is there a way to test main boards. Don't want to buy one as the £40 and find out it's not that.
          Cheers.

          Comment

          • tom66
            EVs Rule
            • Apr 2011
            • 32560
            • UK

            #6
            Re: LG Won't turn on 47ld450

            Not easily - but the best method would be to try and eliminate all other faults first.
            e.g. you can try jumpering the backlight on signal to test the backlight and check the panel for obvious cracks.
            Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
            For service manual, schematic, boardview (board view), datasheet, cad - use our search.

            Comment

            • Ice203
              Senior Member
              • May 2015
              • 99
              • Uk

              #7
              Re: LG Won't turn on 47ld450

              But new main board in and still have the same problem. How do I go about testing backlight. Cheers

              Comment

              • tom66
                EVs Rule
                • Apr 2011
                • 32560
                • UK

                #8
                Re: LG Won't turn on 47ld450

                In the same manner as you jumpered the PSU to turn on the 12V etc... but you also jump BL ON (might be marked ON/OFF or INV ON or B/L), the main board must be disconnected.
                Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                Comment

                • Ice203
                  Senior Member
                  • May 2015
                  • 99
                  • Uk

                  #9
                  Re: LG Won't turn on 47ld450

                  Thxs. Back lights work fine.

                  Comment

                  • Ice203
                    Senior Member
                    • May 2015
                    • 99
                    • Uk

                    #10
                    Re: LG Won't turn on 47ld450

                    Checked all pins and no power at the inv on/off pin.

                    Comment

                    • tom66
                      EVs Rule
                      • Apr 2011
                      • 32560
                      • UK

                      #11
                      Re: LG Won't turn on 47ld450

                      Probably your new main board is faulty but try without TCON connected to main and see if it powers up with just backlights.
                      Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                      For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                      Comment

                      • Ice203
                        Senior Member
                        • May 2015
                        • 99
                        • Uk

                        #12
                        Re: LG Won't turn on 47ld450

                        Don't think it has a tcon board. It's led.
                        Could it be these. As don't know how to test

                        Comment

                        • budm
                          Badcaps Legend
                          • Feb 2010
                          • 40746
                          • USA

                          #13
                          Re: LG Won't turn on 47ld450

                          Those two are high Voltage inverter transformers for CCFL, your TV does not have LED backlights.
                          Pictures of the whole backside of the TV?
                          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

                          • tibimakai
                            Badcaps Legend
                            • Jan 2012
                            • 3680
                            • USA

                            #14
                            Re: LG Won't turn on 47ld450

                            LED TVs, have T-con boards as well.
                            Most likely, the "new" mainboard is bad. Do you get power on and inverter on signals? I have repaired a 47LD550 and 42LD450, with bad mainboard.
                            Last edited by tibimakai; 05-22-2015, 09:54 AM.

                            Comment

                            • Ice203
                              Senior Member
                              • May 2015
                              • 99
                              • Uk

                              #15
                              Re: LG Won't turn on 47ld450

                              Comment

                              • Ice203
                                Senior Member
                                • May 2015
                                • 99
                                • Uk

                                #16
                                Re: LG Won't turn on 47ld450

                                Comment

                                • Ice203
                                  Senior Member
                                  • May 2015
                                  • 99
                                  • Uk

                                  #17
                                  Re: LG Won't turn on 47ld450

                                  Every pin gets power except inv on/off

                                  Comment

                                  • budm
                                    Badcaps Legend
                                    • Feb 2010
                                    • 40746
                                    • USA

                                    #18
                                    Re: LG Won't turn on 47ld450

                                    LCD panel with integrated T-CON.
                                    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

                                    • Ice203
                                      Senior Member
                                      • May 2015
                                      • 99
                                      • Uk

                                      #19
                                      Re: LG Won't turn on 47ld450

                                      Just tried a 3rd board and same problem. What r the chances all 3 have same fault.

                                      Comment

                                      • Ice203
                                        Senior Member
                                        • May 2015
                                        • 99
                                        • Uk

                                        #20
                                        Re: LG Won't turn on 47ld450

                                        eBay seller I brought one of the boards said the EPROMs need reflashing. This sound right to any of u.

                                        Comment

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