52" Sharp LCD Transformer Backlight Bypass?

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  • tieny
    Badcaps Veteran
    • Feb 2012
    • 478
    • USA

    #1

    52" Sharp LCD Transformer Backlight Bypass?

    Hey I've been working on a Sharp LC-C5255U
    Symptoms were, once plugged in only the green LED light starts blinking continuously. If the power button is held down for 5 seconds the green led turns red.

    Then Press the power button again, red led turns orange, and the TV would turn on (backlights on) for about 2-3 seconds and shut back off and the starts the green blinking LED again.


    Opened up the TV to the CCFLs and found that one of them was not lighting on. Switched two of the lamps, but the same initial position did not light on, so the CCFL's are actually good.

    I switched the ballast caps to compare the ccfls but no change.

    Switched the transformers and what do you know! the position of the CCFL that is off also switched, so concluding a bad Transformer on the inverter board.

    So heres the question, I'm guessing its pretty hard to find an exact transformer component to replace so thinking of other options. Is there a way to bypass the transformer like i've seen with the lnt-4066f samsung lcd tv by jumping a wire where the bad transformer is?
    Attached Files
    Last edited by tieny; 12-21-2012, 06:11 PM.
  • diodo49
    Member
    • Dec 2012
    • 17
    • USA

    #2
    Re: 52" Sharp LCD Transformer Backlight Bypass?

    Iam waiting for an answer too.

    Comment

    • budm
      Badcaps Legend
      • Feb 2010
      • 40746
      • USA

      #3
      Re: 52" Sharp LCD Transformer Backlight Bypass?

      Can I see the picture of the whole bottom side of the inverter board?
      This is not the same setup used in the SONY/SAMSUNG balancer board, the transformers on the balancer is used for detecting if the lamp is drawing current or not, when the lamp is bad then there will be no voltage feedback to the PWM IC so it will shutdown the circuits.
      Your board use the typical sensing setup as you can see the pin of the output side is fed in to the sensing circuits.
      Attached Files
      Last edited by budm; 12-21-2012, 10:24 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

      • tieny
        Badcaps Veteran
        • Feb 2012
        • 478
        • USA

        #4
        Re: 52" Sharp LCD Transformer Backlight Bypass?

        Here you go
        Attached Files

        Comment

        • tom66
          EVs Rule
          • Apr 2011
          • 32560
          • UK

          #5
          Re: 52" Sharp LCD Transformer Backlight Bypass?

          I think that this should disable the shut down feature for that transformer.
          Attached Files
          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

          • tieny
            Badcaps Veteran
            • Feb 2012
            • 478
            • USA

            #6
            Re: 52" Sharp LCD Transformer Backlight Bypass?

            When you say cut, do you mean cut the trace to open circuit? Would removing the ballast cap also give the same results?

            Comment

            • tom66
              EVs Rule
              • Apr 2011
              • 32560
              • UK

              #7
              Re: 52" Sharp LCD Transformer Backlight Bypass?

              Cutting the trace is easier. Just use a knife or screwdriver to break it and check it with a multimeter. Leave the cap there in case you later decide to replace the transformer or find it's not the fault.
              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

              • tieny
                Badcaps Veteran
                • Feb 2012
                • 478
                • USA

                #8
                Re: 52" Sharp LCD Transformer Backlight Bypass?

                I just removed the cap and plugged it in but there was no change.

                In the picture where i circled the bad transformer that I removed, so I should cut that trace? (the red line)

                Comment

                • budm
                  Badcaps Legend
                  • Feb 2010
                  • 40746
                  • USA

                  #9
                  Re: 52" Sharp LCD Transformer Backlight Bypass?

                  You cannot remove the signal feeding that detection circuit which is on the return side of the lamp, the circuit is looking to see if the lamp is conducting and how much, when you cut the trace or remove the cap, there will be not output signals that goes back to the PWM IC to tell if the lamps are on or not. The primary side of the transformers are connected in parallel, there are duplicated detector circuits for each set of lamps, we just need to find out what the feedback signal level should be to satisfy the PWM feedback signal requirement. I will have to trace out the connection to see how they are connected, or we can disable the PWM dection input. I do not see any PWM IC on this master inverter board.
                  Also, is there a slave inverter board?
                  Also the resistance reading of the suspected transformer has the same resistance reading as the good transformer?
                  Last edited by budm; 12-22-2012, 09:39 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

                  • tieny
                    Badcaps Veteran
                    • Feb 2012
                    • 478
                    • USA

                    #10
                    Re: 52" Sharp LCD Transformer Backlight Bypass?

                    The photo I took was the slave inverter board. And yes the suspected transformer has the same resistance reading as the others at least I think. (Since I'm measuring the transformers pins and keep getting "1" on my meter on the highest range.)

                    Comment

                    • budm
                      Badcaps Legend
                      • Feb 2010
                      • 40746
                      • USA

                      #11
                      Re: 52" Sharp LCD Transformer Backlight Bypass?

                      But it has MASTER printed on the top left of the board as shown on the pictures in post 1.
                      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

                      • tieny
                        Badcaps Veteran
                        • Feb 2012
                        • 478
                        • USA

                        #12
                        Re: 52" Sharp LCD Transformer Backlight Bypass?

                        Oh oops, I keep swapping boards and kind of got confused and just took a photo of the board I had out last thinking the circuit was the same.

                        Heres the back of the master inverter board. I kind of striped some traces when desoldering the transformer... I'm thinking its the ground pins for the transformer?
                        Attached Files

                        Comment

                        • budm
                          Badcaps Legend
                          • Feb 2010
                          • 40746
                          • USA

                          #13
                          Re: 52" Sharp LCD Transformer Backlight Bypass?

                          I am a little confused, so the Master and the Slave inverter boards are about the same setup? So the both Master and Slave have transformers?
                          Last edited by budm; 12-22-2012, 10:15 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

                          • tieny
                            Badcaps Veteran
                            • Feb 2012
                            • 478
                            • USA

                            #14
                            Re: 52" Sharp LCD Transformer Backlight Bypass?

                            Yes both boards have transformers on them, heres a photo of the front of both boards
                            Attached Files

                            Comment

                            • budm
                              Badcaps Legend
                              • Feb 2010
                              • 40746
                              • USA

                              #15
                              Re: 52" Sharp LCD Transformer Backlight Bypass?

                              So you switched the transformer on the Master or on the Slave 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

                              • tieny
                                Badcaps Veteran
                                • Feb 2012
                                • 478
                                • USA

                                #16
                                Re: 52" Sharp LCD Transformer Backlight Bypass?

                                At first I switched two transformers on the master board to see the ccfl changes. Then I switched the bad one from the master onto the slave, so now the bad transformer is on the slave, the one where the cap was removed. (just making sure the test was conclusive)
                                Last edited by tieny; 12-22-2012, 10:36 PM.

                                Comment

                                • budm
                                  Badcaps Legend
                                  • Feb 2010
                                  • 40746
                                  • USA

                                  #17
                                  Re: 52" Sharp LCD Transformer Backlight Bypass?

                                  By passing the circuits will be hard since both boards have sensing circuit, the Master and Slave lamp drive work in concert, one push one pull (those small inverter transformers can not drive the tube that long by using one transformer, that is why they use MASTER/SLAVE SETUP), so you will also have to stop the transformers that drive the lamp on both side (Master side and Slave side). Not sure how to get that done yet.
                                  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

                                  • tieny
                                    Badcaps Veteran
                                    • Feb 2012
                                    • 478
                                    • USA

                                    #18
                                    Re: 52" Sharp LCD Transformer Backlight Bypass?

                                    I see, I thought each transformer just drove their corresponding lamp. So a transformers from both the master and slave actually drive one lamp?

                                    Anyway I had already ordered the inverter board yesterday though. =)

                                    Welcome back! I haven't see you around the forum much lately budm.

                                    Comment

                                    • Cosmo66
                                      Senior Member
                                      • Nov 2012
                                      • 87
                                      • USA

                                      #19
                                      Re: 52" Sharp LCD Transformer Backlight Bypass?

                                      Whats the part number on the transformer?

                                      Is it Z1335 07086

                                      oh nevermind I can see in the picture they are different than the ones I have here

                                      Comment

                                      • tom66
                                        EVs Rule
                                        • Apr 2011
                                        • 32560
                                        • UK

                                        #20
                                        Re: 52" Sharp LCD Transformer Backlight Bypass?

                                        Originally posted by budm
                                        You cannot remove the signal feeding that detection circuit which is on the return side of the lamp, the circuit is looking to see if the lamp is conducting and how much, when you cut the trace or remove the cap, there will be not output signals that goes back to the PWM IC to tell if the lamps are on or not. The primary side of the transformers are connected in parallel, there are duplicated detector circuits for each set of lamps, we just need to find out what the feedback signal level should be to satisfy the PWM feedback signal requirement. I will have to trace out the connection to see how they are connected, or we can disable the PWM dection input. I do not see any PWM IC on this master inverter board.
                                        Also, is there a slave inverter board?
                                        Also the resistance reading of the suspected transformer has the same resistance reading as the good transformer?
                                        I was going by the Norcal video where that tracei is only used for the open built detect; it picks up the high open circuit voltage. Short circuit is done by primary current sensing, or the fuse.
                                        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

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