LC-37D43U Sharp LCD, No power No standby lights

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  • Glitcher
    Badcaps Veteran
    • Mar 2013
    • 673
    • USa

    #1

    LC-37D43U Sharp LCD, No power No standby lights

    Hey I need a little help with this Sharp 37" LCD TV. I opened up the TV, there are no bad caps that I see anywhere. I checked the 5V output and there isn't any. I tried probing around the board and I can't seem to find any voltages anywhere, on the secondary (If i did it right, black probe on ground and red probe on the board)

    There are two large caps on the power supply and I checked the AC voltage on both and they measure about 169V, so I think the 120VAC is going into the board fine.

    What am I missing?

    and thanks for the help.
    Attached Files
  • tom66
    EVs Rule
    • Apr 2011
    • 32560
    • UK

    #2
    Re: LC-37D43U Sharp LCD, No power No standby lights

    I've highlighted some resistors.

    The two smaller ones: Check the resistance and see that it is under 100 ohms.
    The larger one: Check the resistance, and also with the power supply powered (mains connected) check the voltage on both ends, red probe on each end, black probe on primary ground.
    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

    • Glitcher
      Badcaps Veteran
      • Mar 2013
      • 673
      • USa

      #3
      Re: LC-37D43U Sharp LCD, No power No standby lights

      Thanks for the fast reply. on the first post I made an error, the voltage on those two biggest caps is actually oscillating between 162.0V-162.8V (not 169V)
      I measured the two smaller resistors (in circuit) and they both measure 0.4 ohms.
      The larger resistor measures 2.5 ohms. Measuring the voltage on both ends of the resistor I get about 162.0V-162.8V DC on both sides.

      Comment

      • tom66
        EVs Rule
        • Apr 2011
        • 32560
        • UK

        #4
        Re: LC-37D43U Sharp LCD, No power No standby lights

        162V is still fine.
        Those resistors are fine too.

        See image:-
        3 pin device = Should be a diode. Check for shorts between pins 1, 2, and 3. (1->2, 2->3, 1->3) and read off device code.
        7 pin device = Read off device code.
        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

        • Glitcher
          Badcaps Veteran
          • Mar 2013
          • 673
          • USa

          #5
          Re: LC-37D43U Sharp LCD, No power No standby lights

          the 3 pin device I'm measuring: (in circuit)
          pin 1-2: 215 ohms, and 1450 ohms in the other direction
          pin 2-3: 215 ohms, and 1450 ohms in the other direction
          pin 1-3: 0.4 ohms in both directions

          Its labeled:

          STPS2045CT
          7SACS VW
          PHL 708

          For the 7 pin device, there seems to be a metal piece on top of it?

          Comment

          • tom66
            EVs Rule
            • Apr 2011
            • 32560
            • UK

            #6
            Re: LC-37D43U Sharp LCD, No power No standby lights

            The 3 pin device is good.
            7 pin device is heatsinked.
            Check the 5VS -- please make certain you have not got 5V standby.
            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

            • Glitcher
              Badcaps Veteran
              • Mar 2013
              • 673
              • USa

              #7
              Re: LC-37D43U Sharp LCD, No power No standby lights

              Is it these pins? Whats the best way to measure these pins? I have the board out of the chassis right now, does everything have to be plugged in to order to get the readings?
              Attached Files

              Comment

              • tom66
                EVs Rule
                • Apr 2011
                • 32560
                • UK

                #8
                Re: LC-37D43U Sharp LCD, No power No standby lights

                Probably not...
                Just check along the connectors going to the main board from the PSU. Each pin. If you find 5V, the PSU is giving a standby output.
                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

                • Glitcher
                  Badcaps Veteran
                  • Mar 2013
                  • 673
                  • USa

                  #9
                  Re: LC-37D43U Sharp LCD, No power No standby lights

                  Ok so, I have the PSU board out and with only the main AC plugged into it. I'm measuring all the pins showed, with black probe on the metal piece where the screw hole is.

                  It all reads 0V except for the pin labeled BU5V, which measures oscillating between 0.29V to 0.33V
                  Attached Files

                  Comment

                  • tom66
                    EVs Rule
                    • Apr 2011
                    • 32560
                    • UK

                    #10
                    Re: LC-37D43U Sharp LCD, No power No standby lights

                    Ah, the low oscillating voltage tells me one of three things
                    - either there is a short on the main board; or
                    - the PSU has a bad startup capacitor; or
                    - there's a short on the PSU somewhere

                    Can you source a 22 ohm, >=2W resistor?
                    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

                    • Glitcher
                      Badcaps Veteran
                      • Mar 2013
                      • 673
                      • USa

                      #11
                      Re: LC-37D43U Sharp LCD, No power No standby lights

                      I manage to find a 22 ohm resistor, but i'm not sure of the wattage.

                      Which would be the start-up caps on the psu?

                      And how did you know there a short on the main board? When I tested the voltages it wasn't connected to the main board but only connected with the AC main.
                      Attached Files

                      Comment

                      • tom66
                        EVs Rule
                        • Apr 2011
                        • 32560
                        • UK

                        #12
                        Re: LC-37D43U Sharp LCD, No power No standby lights

                        Well, looks like 1 watt maybe... as long as you don't run it for too long should be fine. (May overheat and burn if left for too long -- max 5 minutes.)

                        Put it across the BU5V output with the main board disconnected.

                        If the 5V is then steady: Main board
                        If not: PSU

                        I do not yet know where the fault is until you do these tests.
                        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

                        • Glitcher
                          Badcaps Veteran
                          • Mar 2013
                          • 673
                          • USa

                          #13
                          Re: LC-37D43U Sharp LCD, No power No standby lights

                          I'm confused so where exactly do I put the resistor?

                          Comment

                          • tom66
                            EVs Rule
                            • Apr 2011
                            • 32560
                            • UK

                            #14
                            Re: LC-37D43U Sharp LCD, No power No standby lights

                            From BU5V to GND.
                            Main board must be disconnected.
                            Then, while doing this, measure BU5V.
                            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

                            • Glitcher
                              Badcaps Veteran
                              • Mar 2013
                              • 673
                              • USa

                              #15
                              Re: LC-37D43U Sharp LCD, No power No standby lights

                              Ok so hopefully I did this right. I soldered one end to the BU5V and the other to the screw hole as seen in the photo.

                              I disconnected the two cables shown that go to the main board.

                              Measuring with black probe on ground and red probe on the BU5V I'm now getting a measurement of oscillating 0V to 0.09V.
                              Attached Files

                              Comment

                              • tom66
                                EVs Rule
                                • Apr 2011
                                • 32560
                                • UK

                                #16
                                Re: LC-37D43U Sharp LCD, No power No standby lights

                                Hmm, seems to indicate a problem with the PSU. Can you try a 100 ohm resistor too? Just to be certain...
                                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

                                • selldoor
                                  Slow Learner
                                  • Dec 2010
                                  • 7870

                                  #17
                                  Re: LC-37D43U Sharp LCD, No power No standby lights

                                  Originally posted by Glitcher

                                  Measuring with black probe on ground and red probe on the BU5V I'm now getting a measurement of oscillating 0V to 0.09V.

                                  That IS with the mains power ON?
                                  Please upload pictures using attachment function when ask for help on the repair
                                  http://www.badcaps.net/forum/showthread.php?t=39740

                                  Comment

                                  • Glitcher
                                    Badcaps Veteran
                                    • Mar 2013
                                    • 673
                                    • USa

                                    #18
                                    Re: LC-37D43U Sharp LCD, No power No standby lights

                                    With the main 120V AC connected yes.

                                    Comment

                                    • Glitcher
                                      Badcaps Veteran
                                      • Mar 2013
                                      • 673
                                      • USa

                                      #19
                                      Re: LC-37D43U Sharp LCD, No power No standby lights

                                      Ok, I just put in the 100 ohm resistor, now i'm getting a measurement of oscillating 0V to about 0.16V

                                      I was just searching on ebay for the PSU, there arent much at all, but there are tons of repair services for this particular board and TV. Guessing this might be a common problem?
                                      I found this one:
                                      http://www.coppelltvrepair.com/p/102...r-sharp-lcd-tv

                                      Stating:
                                      "The most common failure in that board results in a completely dead TV - no front LED, no response to buttons, nothing."

                                      I just wish they would say which part is bad lol.
                                      Last edited by Glitcher; 04-01-2013, 10:03 AM.

                                      Comment

                                      • tom66
                                        EVs Rule
                                        • Apr 2011
                                        • 32560
                                        • UK

                                        #20
                                        Re: LC-37D43U Sharp LCD, No power No standby lights

                                        OK, the first place I would look is at the startup capacitor. This will be a small electrolytic capacitor next to the 7 pin IC.
                                        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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