Sharp LC-60E79U problems

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  • Redrebel10
    Senior Member
    • Jun 2017
    • 89
    • United States

    #21
    Re: Sharp LC-60E79U problems

    Just to be sure I'm reading DCV with meter set on 200 range?

    Comment

    • budm
      Badcaps Legend
      • Feb 2010
      • 40746
      • USA

      #22
      Re: Sharp LC-60E79U problems

      Originally posted by Redrebel10
      yes I see them, the R almost look like diodes and the C7120 is a cap all on the secondary side
      Then you should see the that MOSFET right next to those two resistors sitting right next to each other..
      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

      • Redrebel10
        Senior Member
        • Jun 2017
        • 89
        • United States

        #23
        Re: Sharp LC-60E79U problems

        I thought mosfets were tested off the board and out of circuit so how do I test the q7120 with my meter

        Comment

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA

          #24
          Re: Sharp LC-60E79U problems

          We are testing to see what DCV we have at the 3 pins of the MOSFET with ref. to chassis GND.
          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

          • Redrebel10
            Senior Member
            • Jun 2017
            • 89
            • United States

            #25
            Re: Sharp LC-60E79U problems

            I get 12v on both outer pins, the middle pin started with voltage but when I touched it the voltage dropped, all this was done with me forcing the backlights on, on normal start up the psb shuts down after 2 or 3 seconds

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA

              #26
              Re: Sharp LC-60E79U problems

              Test it in normal condition with every thing hooked back up because you need to force on the main power supply, and the panel power too not just the backlights circuit.
              What is the P/N as printed on the MOSFET?
              It should be P-CH, so right now you have Source pin and the Gate pin at 12V which means the MOSFET is not turned on, the Gate has to about 4V less than the Source pin for it to be on.
              You can force on the circuit by connecting 470~1000 Ohms resistor between PNL-POW and standby Voltage to do the force on.
              BTW, when you said force on backlights, do mean by using resistor?
              Last edited by budm; 07-19-2017, 10:16 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

              • Redrebel10
                Senior Member
                • Jun 2017
                • 89
                • United States

                #27
                Re: Sharp LC-60E79U problems

                OK I'll check try that later when I get home from work. Forcing backlights on by starting the whole holding volume down and input while plugging in the ac chord into the tv

                Comment

                • budm
                  Badcaps Legend
                  • Feb 2010
                  • 40746
                  • USA

                  #28
                  Re: Sharp LC-60E79U problems

                  Right now we are not dealing with the backlights circuit but we are trying to get that switched +12V to work so it will supply the +12V to run the T-CON board.
                  So as long as you have +12V on the Source pin of that switched MOSFET and the Gate drive Voltage (around +8V) to turn on the MOSFET when the PNL-POW command signal is present then it should supply +12V at the Drain pin, if not then we have to find out why.
                  Last edited by budm; 07-20-2017, 08:56 AM.
                  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

                  • Redrebel10
                    Senior Member
                    • Jun 2017
                    • 89
                    • United States

                    #29
                    Re: Sharp LC-60E79U problems

                    OK powering up the tv normally, both outer pins read 12v and when I touch the middle pin it starts at around 6v and immediately drops upon putting my lead on it. All this had to be done within 3 seconds due to the power board making the clicking noise and shutting down the tv which then it displays the flashing error codes on the front, I'm attaching a picture of the q7120 mosfet, best I can read it says 40P03G1 140 28F, Im going to a friend's tomorrow to get a resistor to try and jump the 2 pins as you suggested, I don't currently have one
                    Attached Files

                    Comment

                    • Redrebel10
                      Senior Member
                      • Jun 2017
                      • 89
                      • United States

                      #30
                      Re: Sharp LC-60E79U problems

                      Here is a clearer picture of q7120
                      Attached Files

                      Comment

                      • budm
                        Badcaps Legend
                        • Feb 2010
                        • 40746
                        • USA

                        #31
                        Re: Sharp LC-60E79U problems

                        Originally posted by Redrebel10
                        Here is a clearer picture of q7120
                        https://www.badcaps.net/forum/attach...4&d=1500602551
                        The left pin is GATE, the middle pin is DRAIN, the right pin is SOURCE.
                        So if you leave black probe on the chassis and Red probe on the GATE pin and watch the meter to see if the GATE pin Voltage goes down to less than 10V or not, if it does not change at all then it may be that the circuit is not getting the PNL-POW signal from the main board so you need to move the red probe to the PNL-POW pin and watch the meter to see if PNL-POW goes to>2V or not when the TV is turned on.
                        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

                        • Redrebel10
                          Senior Member
                          • Jun 2017
                          • 89
                          • United States

                          #32
                          Re: Sharp LC-60E79U problems

                          OK the gate pins go straight to 11.9v volts when powering on the tv. When powering on the PNL-POW pin reads zero, however when that click happens to shut down the tv , the voltage jumps to 2.5 just long enough for me to see it before dropping to zero.

                          Comment

                          • Redrebel10
                            Senior Member
                            • Jun 2017
                            • 89
                            • United States

                            #33
                            Re: Sharp LC-60E79U problems

                            I just used a 680 ohm resistor and jumped from BU5V (which reads 5v when powered on) to PNL-POW and nothing changed, TV still shut down after 2 or 3 seconds

                            Comment

                            • budm
                              Badcaps Legend
                              • Feb 2010
                              • 40746
                              • USA

                              #34
                              Re: Sharp LC-60E79U problems

                              Did you disconnect that PNL-PWR wire going back to the main board first? Otherwise the main board will keep that line low and not allowing it to go high, and you need to keep the meter on the PNL12V will jump up to 12V or not.
                              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

                              • budm
                                Badcaps Legend
                                • Feb 2010
                                • 40746
                                • USA

                                #35
                                Re: Sharp LC-60E79U problems

                                Right now if the only missing signal is the PNL-POWER, the rest of the Voltage at the connector going by the pin names should be something as shown in this thread:
                                https://www.badcaps.net/forum/showthread.php?t=54228
                                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

                                • Redrebel10
                                  Senior Member
                                  • Jun 2017
                                  • 89
                                  • United States

                                  #36
                                  Re: Sharp LC-60E79U problems

                                  Hey Bud, no I didn't pull the wire from the connector before jumping but I did hold my meter on the PNL12v and it stayed at .7v. I figured it might damage the connector If I removed a wire from it but I can try that tonight I work doubles on weekends so it will be late. I checked the other post and all my readings are good other than PNL-POW.

                                  I saw where you mentioned LDO switched regulator, where is this part and are you suggesting its worth a shot to replace it?

                                  Comment

                                  • budm
                                    Badcaps Legend
                                    • Feb 2010
                                    • 40746
                                    • USA

                                    #37
                                    Re: Sharp LC-60E79U problems

                                    Your board does not use Switched LDO, it uses the MOSFET as simple electronics switch.
                                    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

                                    • Redrebel10
                                      Senior Member
                                      • Jun 2017
                                      • 89
                                      • United States

                                      #38
                                      Re: Sharp LC-60E79U problems

                                      Ok thanks I will follow after correctly jumping resistor to PWR-PNL

                                      Comment

                                      • Redrebel10
                                        Senior Member
                                        • Jun 2017
                                        • 89
                                        • United States

                                        #39
                                        Re: Sharp LC-60E79U problems

                                        One other thing that comes to mind is initially I tested the PWR-PNL and got 3.2v when I did vol down/input start up which lights up the screen. I also tested q7120 at that time and I still got 12v on both outer pins, but still only had .7v on PNL12v. I could disconnect plug from psb and the pnl12v drops to zero, Is it possible that the .7v reading at pnl12v is somehow back fed from the tcon board maybe from the mother board? If I'm following everything you have been saying, the problem is the q7120.
                                        Last edited by Redrebel10; 07-22-2017, 03:26 PM. Reason: correct spelling

                                        Comment

                                        • budm
                                          Badcaps Legend
                                          • Feb 2010
                                          • 40746
                                          • USA

                                          #40
                                          Re: Sharp LC-60E79U problems

                                          If you did see the PNL-PWR for seconds but the PNL-12V did not even jumps up for seconds then for sure there is problem with that switching circuit. That 0.70V may be back fed from the T-CON as you suggested. Also, it looks like the circuit that produce the PNL-PWR is dead since it does switch the signal low and high, so you probably no need to simulate the PNL-POW signal at this point.
                                          I believe the Q7120 is OK but the circuit that drive the Gate of Q7120 is not working.
                                          Q7120 can be forced on by soldering in 330~470 Ohms resistor between Gate and GND to force it on and see when you turn on to see if you will get the PNL-12V or not.
                                          Last edited by budm; 07-22-2017, 03:56 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

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