LG 50PA4500 not turning on

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  • supered
    Member
    • Mar 2015
    • 22
    • USA
    #1

    LG 50PA4500 not turning on

    Hello
    I am trying to fix a 50" Lg tv that had clicking and would not power on.
    I found this post
    https://www.badcaps.net/forum/showth...light=50PA4500
    And this is where I'm at.
    Clicking was constant on the power supply and by disconnecting Y-sustain the clicking stopped ( 1 click when powered up) and the red led on the main board stopped flashing, replaced Y-sustain and buffer boards (came as a set) and now the tv will still not power up but no constant clicking.
    With every thing plugged in I get red power led and red led on main board and a flashing green led on the logic board.
    Power supply with everything disconnected except power I get 0 volts Vs and 0 volts Va with everything connected 206 Vs and 55 Va.
    I tried jumping m-on and stby pin 1 & 3 as suggested in above thread and nothing happens.

    Any help would be appreciated.
    Thanks
    Tags: None
    • Hamie
      Badcaps Legend
      • Apr 2014
      • 1383
      • UK
      #2
      Re: LG 50PA4500 not turning on

      the power supply will need the mainboard to turn on.
      WIth only the powersupply and mainboard connected does be tv turn on. Ie: no clicking and perfect vs va voltages?

        Comment

        • supered
          Member
          • Mar 2015
          • 22
          • USA
          #3
          Re: LG 50PA4500 not turning on

          With power supply and only the main board plugged in I get just 1 click and 206 Vs and 55 Va

            Comment

            • Hamie
              Badcaps Legend
              • Apr 2014
              • 1383
              • UK
              #4
              Re: LG 50PA4500 not turning on

              Ok well the powersupply and mainboard appear to be working.
              That's not to say that the powersupply isn't failing under load but that's doubtful.

                Comment

                • Hamie
                  Badcaps Legend
                  • Apr 2014
                  • 1383
                  • UK
                  #5
                  Re: LG 50PA4500 not turning on

                  So unplug the ysus form the XMain and plug the XMain back into the power supply Does the tv stay on. Vs va voltages still good?

                    Comment

                    • supered
                      Member
                      • Mar 2015
                      • 22
                      • USA
                      #6
                      Re: LG 50PA4500 not turning on

                      yes

                        Comment

                        • Hamie
                          Badcaps Legend
                          • Apr 2014
                          • 1383
                          • UK
                          #7
                          Re: LG 50PA4500 not turning on

                          Ok now unhook the buffer boards from the ysus and power on.

                          with the buffers unhooked locate the test point on the ysus for vsc (vscan)

                          Power on. If the tv stays on, and the vsc matches the panel sticker it would suggest bad buffer boards.

                            Comment

                            • Hamie
                              Badcaps Legend
                              • Apr 2014
                              • 1383
                              • UK
                              #8
                              Re: LG 50PA4500 not turning on

                              Also note the vsc voltage might only appear briefly when the tv is plugged in. Then slowly drop to 0.

                                Comment

                                • supered
                                  Member
                                  • Mar 2015
                                  • 22
                                  • USA
                                  #9
                                  Re: LG 50PA4500 not turning on

                                  vsc is 150 vdc and vsc is not on the sticker but 150 is

                                    Comment

                                    • Hamie
                                      Badcaps Legend
                                      • Apr 2014
                                      • 1383
                                      • UK
                                      #10
                                      Re: LG 50PA4500 not turning on

                                      There should also be a test point for -vy.
                                      Should match the panel sticker.

                                        Comment

                                        • Hamie
                                          Badcaps Legend
                                          • Apr 2014
                                          • 1383
                                          • UK
                                          #11
                                          Re: LG 50PA4500 not turning on

                                          Fyi

                                            Comment

                                            • Hamie
                                              Badcaps Legend
                                              • Apr 2014
                                              • 1383
                                              • UK
                                              #12
                                              Re: LG 50PA4500 not turning on

                                              -vy also located on ysus.

                                                Comment

                                                • supered
                                                  Member
                                                  • Mar 2015
                                                  • 22
                                                  • USA
                                                  #13
                                                  Re: LG 50PA4500 not turning on

                                                  Are they measured to chassis ground and with the buffers disconnected

                                                    Comment

                                                    • Hamie
                                                      Badcaps Legend
                                                      • Apr 2014
                                                      • 1383
                                                      • UK
                                                      #14
                                                      Re: LG 50PA4500 not turning on

                                                      Yes.

                                                        Comment

                                                        • Alastair E
                                                          Chief Womble
                                                          • Mar 2013
                                                          • 1963
                                                          • U.K.
                                                          #15
                                                          Re: LG 50PA4500 not turning on

                                                          -Vy is measured across a component--often a cap or resistor (Depending on model specifics)--the board is marked with + and - symbols and (-Vy)...

                                                          V-ZBias is found on X-SUS board and measured to chassis...
                                                          TELEFIX

                                                          How PLASMA SCREENS WORK, X-SUS and Y-SUS what they do--
                                                          http://www.irf.com/technical-info/appnotes/an-1088.pdf
                                                          PLEASE DO NOT EMAIL ME PRIVATELY FOR REPAIR ADVICE. QUESTIONS BELONG ON THE FORUM!

                                                            Comment

                                                            • Hamie
                                                              Badcaps Legend
                                                              • Apr 2014
                                                              • 1383
                                                              • UK
                                                              #16
                                                              Re: LG 50PA4500 not turning on

                                                              Yip sorry my mistake.

                                                                Comment

                                                                • Alastair E
                                                                  Chief Womble
                                                                  • Mar 2013
                                                                  • 1963
                                                                  • U.K.
                                                                  #17
                                                                  Re: LG 50PA4500 not turning on

                                                                  No mistake there, Hamie--Most are measured to chassis--Its only the -Vy thats a floating-supply that isnt...
                                                                  TELEFIX

                                                                  How PLASMA SCREENS WORK, X-SUS and Y-SUS what they do--
                                                                  http://www.irf.com/technical-info/appnotes/an-1088.pdf
                                                                  PLEASE DO NOT EMAIL ME PRIVATELY FOR REPAIR ADVICE. QUESTIONS BELONG ON THE FORUM!

                                                                    Comment

                                                                    • Hamie
                                                                      Badcaps Legend
                                                                      • Apr 2014
                                                                      • 1383
                                                                      • UK
                                                                      #18
                                                                      Re: LG 50PA4500 not turning on

                                                                      Yeah I forgot he had already checked the vsc and we'd moved on to -vy

                                                                        Comment

                                                                        • supered
                                                                          Member
                                                                          • Mar 2015
                                                                          • 22
                                                                          • USA
                                                                          #19
                                                                          Re: LG 50PA4500 not turning on

                                                                          My stickers reads
                                                                          voltage settings: 5v/ Va:55v/ Vs:205v
                                                                          N/A / - 190v / 150v / N/A / 120v
                                                                          The reading i am getting as measured at the green resistors marked -vy and vsc
                                                                          is 75vdc
                                                                          photo of board
                                                                          http://assets.shopjimmy.com/media/ca...3201-top_1.jpg

                                                                            Comment

                                                                            • Hamie
                                                                              Badcaps Legend
                                                                              • Apr 2014
                                                                              • 1383
                                                                              • UK
                                                                              #20
                                                                              Re: LG 50PA4500 not turning on

                                                                              -vy should be -190 volts.

                                                                                Comment

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