HELP! LG 50PQ3000 Plasma TV Repair

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  • alwaysfresh
    Member
    • Jan 2015
    • 12
    • Romania

    #1

    HELP! LG 50PQ3000 Plasma TV Repair

    Hello guys, this is my first thread on badcaps forum.

    I am asking for your help in repairing the LG50PQ3000 plasma I got.

    Its initial problem was that the TV wouldn't turn on, and it made that clicking sound. It had no voltages on the PSU, just the some unstable standby 5V. Changed the VSB3200 schottky diode with some equivalent (not schottky) and it works.

    Ok I turned on the TV and voila... entered the menu, configured the programs. After finishing the auto programming job (10 min maybe), the display suddenly shut down, heard some noise before this, but not like exploding or something similar, just some noise. The sound was still working, I could hear the TV program.

    I disassembled the TV again to see what happened. Nothing visible... just a round crack in the middle of the YSus board. Had a look on the bottom of the Ysus board, and seemed that the crack cut 2 routed lines (one was the connection with the ground). I said to myself it's the crack, I'll repair it. Repaired the crack but no result.

    Then I turned the TV on and listened carefully.I could hear some repetitive and discrete "beep-beep" sound coming from the radiator next to the drivers (this sound could be heard right from the moment when the display stopped).
    I had a look into the service manual, I verified that my PSU was ok all voltages were good, then I verified all the components attached to the radiators (diodes and transistors) and seems that 4 transistors are shorted: 3x30j124 and 1x30f124. Also the input fuse of the Ysus board was broken.

    Ok I ordered those IGBTs, but I want to ask you, if I change them with the new ones, the TV will work or I will get the same problem, breaking the new IGBTs? How can I assure that my problem was the cracked PCB and now it will work fine?

    I will attach some pictures of the board.
    Guys I can't wait to see your replays! Thank you!
    Attached Files
  • alwaysfresh
    Member
    • Jan 2015
    • 12
    • Romania

    #2
    Re: HELP! LG 50PQ3000 Plasma TV Repair

    Forgot to say, the Ysus board is EAX60987801 model.
    And if I replace the IGBTs, do I need to adjust any resistors or pots?

    Comment

    • tom66
      EVs Rule
      • Apr 2011
      • 32560
      • UK

      #3
      Re: HELP! LG 50PQ3000 Plasma TV Repair

      I would always replace the little surface mount gate driver ICs when replacing the IGBTs, as they can be damaged by this failure...
      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

      • alwaysfresh
        Member
        • Jan 2015
        • 12
        • Romania

        #4
        Re: HELP! LG 50PQ3000 Plasma TV Repair

        But is it plausible that the crack on the PCB to be the real cause for destroying my IGBTs?

        Comment

        • tom66
          EVs Rule
          • Apr 2011
          • 32560
          • UK

          #5
          Re: HELP! LG 50PQ3000 Plasma TV Repair

          Possibly, it depends where the crack is, but the failure could still have damaged the driver ICs so I would replace them or your new IGBTs could fail immediately on power up.
          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

          • alwaysfresh
            Member
            • Jan 2015
            • 12
            • Romania

            #6
            Re: HELP! LG 50PQ3000 Plasma TV Repair

            Is there a way of testing the driver?

            Comment

            • tom66
              EVs Rule
              • Apr 2011
              • 32560
              • UK

              #7
              Re: HELP! LG 50PQ3000 Plasma TV Repair

              With an oscilloscope yes... Otherwise you can check for shorts and hope it survived (doesn't guarantee the internal logic in it survived, just checks for output driver short.)
              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

              • alwaysfresh
                Member
                • Jan 2015
                • 12
                • Romania

                #8
                Re: HELP! LG 50PQ3000 Plasma TV Repair

                hmm may be i can get an oscilloscope. can you tell me what kind of component is usually that driver?
                Last edited by alwaysfresh; 01-31-2015, 09:53 AM.

                Comment

                • ReeceyBurger123
                  Never Give Up !
                  • May 2014
                  • 7325
                  • Britain

                  #9
                  Re: HELP! LG 50PQ3000 Plasma TV Repair

                  I have one in atm with a shorted bridge rectifier, will use this post to help me further trouble shoot thanks.
                  Please Do Not PM My Page Asking For Help Badcaps Is The Place For Advise, Page Linked For Business Reasons Only. Anyone Doing So Will Be Banned Instantly !

                  https://www.facebook.com/Telford-Tel...7894576335359/

                  Comment

                  • tom66
                    EVs Rule
                    • Apr 2011
                    • 32560
                    • UK

                    #10
                    Re: HELP! LG 50PQ3000 Plasma TV Repair

                    Usually an 8 pin chip surface mount on the bottom, sometimes bigger or smaller. Will be connected to GATE of IGBT/FET through some resistors or diodes.
                    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

                    • MagicSmoke
                      Badcaps Veteran
                      • Feb 2011
                      • 275
                      • USA

                      #11
                      Re: HELP! LG 50PQ3000 Plasma TV Repair

                      If the board is multi layered you will not be able to repair it. If it is only 2 layers ( top and bottom) then you might be able to fix it.

                      Comment

                      • alwaysfresh
                        Member
                        • Jan 2015
                        • 12
                        • Romania

                        #12
                        Re: HELP! LG 50PQ3000 Plasma TV Repair

                        No, it's not a multi layer board. I just reconstructed the circuit were it was broken.

                        Now I have to wait for my 30J124 and 30F124 transistors to come. It will take a long time, hope less than 1 month.

                        I have enough time to verify each component, I will try to verify the drivers also.
                        Last edited by alwaysfresh; 02-01-2015, 08:40 AM.

                        Comment

                        • alwaysfresh
                          Member
                          • Jan 2015
                          • 12
                          • Romania

                          #13
                          Re: HELP! LG 50PQ3000 Plasma TV Repair

                          The components arrived, now the TV works as new.
                          I just changed the broken transistors and the 4A input fuse so now everything is fine.
                          I will post some photos. Thank you guys for all your help

                          Comment

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