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Sharp LC-50P66U-completely dead PSU!!

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    Sharp LC-50P66U-completely dead PSU!!

    Hi guys
    I just got this TV which is completely dead, not a single sign of life!
    I have not a single voltage on the output of the PSU!
    I checked the fuse which it was ok, I have 385V on the main Capacitor, beyond that I have nothing. The Mosfets and diodes were checked and tested ok (I might have missed something out). I'm still troubleshooting, but I'm open to your suggestions!
    I didn't find any service manual or the schematic for the power supply yet, I just attached some pictures of the TV.
    Thanks in advance
    Attached Files
    Last edited by kgavionics; 07-18-2020, 12:25 PM.

    #2
    Re: Sharp LC-50P66U-completely dead PSU!!

    Update: I found the PSU schematic!
    Attached Files

    Comment


      #3
      Re: Sharp LC-50P66U-completely dead PSU!!

      Originally posted by kgavionics View Post
      Hi guys
      I just got this TV which is completely dead, not a single sign of life!
      I have not a single voltage on the output of the PSU!
      I checked the fuse which it was ok, I have 385V on the main Capacitor, beyond that I have nothing. The Mosfets and diodes were checked and tested ok (I might have missed something out). I'm still troubleshooting, but I'm open to your suggestions!
      I didn't find any service manual or the schematic for the power supply yet, I just attached some pictures of the TV.
      Thanks in advance
      The 385VDC on the main filter in the hot side of the circuit, it it measured right between the two legs of the cap? if it is then the PFC Voltage booster circuit is working, so that means IC N801 (IDP2301) is getting VCC on pin 3, this VCC is from Transistor V809 which it receives VCC1 from the rectifier on one of the transformer T803 winding so T803 is being driven, T803 also generates the 12V and 16V power supplies. So are you 100% sure that you do not have any 12V or 16V outputs?
      BTW, the schematic looks to be not from manufacturer but reverse engineering by some one so I do not know how accurate the circuit is.
      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


        #4
        Re: Sharp LC-50P66U-completely dead PSU!!

        Thank Budm for your input! It's really appreciated!
        I'm still trying to find what's going on with this PSU! But, I'm a bit stuck, because I didn't do any modification, but I'm only getting 170Vdc on the PFC cap! Weird!!

        Comment


          #5
          Re: Sharp LC-50P66U-completely dead PSU!!

          So now the Voltage on the main cap is no longer at 385VDC as reported in post 1?
          What happen if you hit power switch, do you see the Voltage on the cap jumps up to 385?
          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


            #6
            Re: Sharp LC-50P66U-completely dead PSU!!

            Originally posted by budm View Post
            So now the Voltage on the main cap is no longer at 385VDC as reported in post 1?
            What happen if you hit power switch, do you see the Voltage on the cap jumps up to 385?
            Sorry, I forgot to mention that while I was troubleshooting the set I accidentally shorted V802 drain and the source which burned the R 826 resistor (0.1 ohms), but I replaced it with a 0.17 resistor and tested the Mosfet V802 and it was fine! Could it be the reason why I don't have the 380V?

            Comment


              #7
              Re: Sharp LC-50P66U-completely dead PSU!!

              Originally posted by kgavionics View Post
              Sorry, I forgot to mention that while I was troubleshooting the set I accidentally shorted V802 drain and the source which burned the R 826 resistor (0.1 ohms), but I replaced it with a 0.17 resistor and tested the Mosfet V802 and it was fine! Could it be the reason why I don't have the 380V?
              So you shorted out the PFC section.
              Did you check R825 (470 Ohms) to see if it is damaged?
              Check the resistance between pin 2 (IC N801) and Hot side circuit ground, the IC could be damaged when you shorted out the S and D of PFC MOSFET.
              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


                #8
                Re: Sharp LC-50P66U-completely dead PSU!!

                Originally posted by budm View Post
                So you shorted out the PFC section.
                Did you check R825 (470 Ohms) to see if it is damaged?
                Check the resistance between pin 2 (IC N801) and Hot side circuit ground, the IC could be damaged when you shorted out the S and D of PFC MOSFET.
                Hi
                I checked the R825 and found 220kohms, so I'm going to replace it and report back!

                Comment


                  #9
                  Re: Sharp LC-50P66U-completely dead PSU!!

                  That means large amount of current flown through the resistor and the internal circuit of the IC to ground, so the IC may not survive.
                  BTW, is it SMD Resistor and labeled with 221?
                  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


                    #10
                    Re: Sharp LC-50P66U-completely dead PSU!!

                    Originally posted by budm View Post
                    That means large amount of current flown through the resistor and the internal circuit of the IC to ground, so the IC may not survive.
                    BTW, is it SMD Resistor and labeled with 221?
                    I checked PIN2 and hot ground and didn't find a short!so hopefully, the IC is not burnt out!
                    I checked the value of the R825 on my USB microscope and it's marked 471 which is 470ohms!
                    I'm going to report all my findings after I replace the resistor!
                    Thanks again Budm!!

                    Comment


                      #11
                      Re: Sharp LC-50P66U-completely dead PSU!!

                      The IC could have blown open circuit and damaged..
                      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


                        #12
                        Re: Sharp LC-50P66U-completely dead PSU!!

                        Originally posted by budm View Post
                        The IC could have blown open circuit and damaged..
                        Yeah! I'm 100% sure that the IC is faulty, because even I replaced the V802, I still have 165V on the main cap, which indicates that the booster circuit is not working!
                        I looked on eBay for replacement board and I ordered it, but soon realized that even though it has the same part number it's missing some components which may indicates that the board is not 100% compatible with mine!
                        https://www.ebay.ca/itm/BEST-BUY-SHA...53.m1438.l2649

                        I wrote to the seller to cancel the item! Meanwhile, I'm looking for a new PSU!

                        Comment


                          #13
                          Re: Sharp LC-50P66U-completely dead PSU!!

                          The bar code sticker is what you need to go by since it shows the PCBA (Printed Circuit Board Assembly) P/N.
                          Last edited by budm; 07-20-2020, 12:09 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


                            #14
                            Re: Sharp LC-50P66U-completely dead PSU!!

                            Originally posted by budm View Post
                            The bar code sticker is what you need to go by since it shows the PCBA (Printed Circuit Board Assembly) P/N.
                            Thank budm! I ordered one eBay for $25!

                            Comment


                              #15
                              Re: Sharp LC-50P66U-completely dead PSU!!

                              I received the power supply board today, but I have the same problem! No output voltage or whatsoever, even with the backlight and main board connectors disconnected!
                              I have 388V across the main capacitor! And I have 245V on v905 anode (backlight)
                              I don't think that the new PSU is faulty either, according to the seller it was pulled from a broken screen TV!
                              To be honest, I never came across a problem when I don't have any output voltage!really weird problem!!

                              Comment


                                #16
                                Re: Sharp LC-50P66U-completely dead PSU!!

                                Originally posted by kgavionics View Post
                                I received the power supply board today, but I have the same problem! No output voltage or whatsoever, even with the backlight and main board connectors disconnected!
                                I have 388V across the main capacitor! And I have 245V on v905 anode (backlight)
                                I don't think that the new PSU is faulty either, according to the seller it was pulled from a broken screen TV!
                                To be honest, I never came across a problem when I don't have any output voltage!really weird problem!!
                                1) So the PFC is owrking and also the boost converter for the backlights is working.
                                2) What do you get on the Cathode return of the LED string? You do have the LED connector in place when you measure the Anode Voltage, correct?
                                3) I cannot see how you still do not have 12V and 16V at the connector since the 200V for the backlight power supply is generated from same circuit and transformer that generates t he 12V and 16V, see the schematic. Are you 100% sure that you probe at the correct pins of the connector?
                                4)What Voltage do you have on C878/879, C873/874, C875/876 when you turn on the power 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


                                  #17
                                  Re: Sharp LC-50P66U-completely dead PSU!!

                                  https://www.badcaps.net/forum/attach...9&d=1595096371
                                  Can you provide good clear hi res straight shots of the whole top and bottom side of the power supply board? As you can see, your picture is not in focused for me to be able to read anything on the 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


                                    #18
                                    Re: Sharp LC-50P66U-completely dead PSU!!

                                    Originally posted by budm View Post
                                    https://www.badcaps.net/forum/attach...9&d=1595096371
                                    Can you provide good clear hi res straight shots of the whole top and bottom side of the power supply board? As you can see, your picture is not in focused for me to be able to read anything on the board.
                                    i have attached the top and bottom pictures of the old board.
                                    Attached Files

                                    Comment


                                      #19
                                      Re: Sharp LC-50P66U-completely dead PSU!!

                                      Originally posted by kgavionics View Post
                                      i have attached the top and bottom pictures of the old board.
                                      That is better.
                                      How about my questions on my post #16?
                                      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


                                        #20
                                        Re: Sharp LC-50P66U-completely dead PSU!!

                                        1-Yeah, the booster circuit is working fine
                                        2-I have a fluctuating voltage between (112 to 123V) on the anode and (223 to 240V) on the cathode of V905.sorry I made a mistake earlier by saying I had 245 on the anode. I tested the diode and it's good, but how come I have a 100V drop across v905?
                                        3-i'm 100% sure that I have 0v on that connector.
                                        4-how can I take the measurement from the bottom side of the board? Do know a safe way to do it?

                                        Comment

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