Sont KDL42EX440 power supply

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  • ljintexas
    LJinTexas
    • Jan 2015
    • 669
    • USA
    #1

    Sont KDL42EX440 power supply

    I have 165 volts DC leg to leg on main cap..165 volts on center leg of one of the two transistors that are paired up, nothing on the other one beside it...measuring against negative side of main filter cap. No voltage anywhere to ground..I do not have any other dc voltage anywhere on the board.
    Set was totally dead..no standby LED. Any help is most appreciated.
    Attached Files
    Tags: None
    • CapLeaker
      Leaking Member
      • Dec 2014
      • 8101
      • Canada
      #2
      Re: Sont KDL42EX440 power supply

      Check CN6401 and see if you really don't have 3.3V STBY. Check the resistance between the 3.3V pin and the GND pin, trace it back and make sure nothing is shorted in the secondary (rectifier diode, or bad capacitor) there.
      If you haven't luck in the secondary, check the primary STBY voltage part of the PSU where IC6301 (MIP2H2) is. Your reference GND for measuring DC in the primary circuit is the negative post of the big main filter capacitor.

        Comment

        • ljintexas
          LJinTexas
          • Jan 2015
          • 669
          • USA
          #3
          Re: Sont KDL42EX440 power supply

          I actually DO have 3.3 volts standby on the pin indicated. However, I do not have VCC 12V.
          Last edited by ljintexas; 06-18-2016, 10:17 AM.

            Comment

            • ljintexas
              LJinTexas
              • Jan 2015
              • 669
              • USA
              #4
              Re: Sont KDL42EX440 power supply

              Now to figure out where the 12 volts comes from.
              Last edited by ljintexas; 06-18-2016, 10:18 AM.

                Comment

                • ljintexas
                  LJinTexas
                  • Jan 2015
                  • 669
                  • USA
                  #5
                  Re: Sont KDL42EX440 power supply

                  Or does it not develop the 12V until the main board tells it to come on?

                    Comment

                    • ljintexas
                      LJinTexas
                      • Jan 2015
                      • 669
                      • USA
                      #6
                      Re: Sont KDL42EX440 power supply

                      Replaced one Schottkey Diode that tested bad out of circuit. I still have my 3.3 volts standby. Reinstalled board. No PS-ON/OFF voltage coming back from main. No standby LED.

                        Comment

                        • CapLeaker
                          Leaking Member
                          • Dec 2014
                          • 8101
                          • Canada
                          #7
                          Re: Sont KDL42EX440 power supply

                          You got a bad main board. PSon, DIM, BLon all comes from the main board. That tells the PSU and the backlights to turn on.

                          To force the PSU on without the main board, jump 3.3V through a 1k resistor from 3.3V to PSon and from another 1k resistor from 3.3V to BLon. plug it in and all the voltage rails should be up and the backlights should be on.
                          Last edited by CapLeaker; 06-18-2016, 04:03 PM.

                            Comment

                            • ljintexas
                              LJinTexas
                              • Jan 2015
                              • 669
                              • USA
                              #8
                              Re: Sont KDL42EX440 power supply

                              ZY100110A is on the sticker on the main board.

                                Comment

                                • ljintexas
                                  LJinTexas
                                  • Jan 2015
                                  • 669
                                  • USA
                                  #9
                                  Re: Sont KDL42EX440 power supply

                                  Here are the two labels on the board.
                                  Attached Files

                                    Comment

                                    • ljintexas
                                      LJinTexas
                                      • Jan 2015
                                      • 669
                                      • USA
                                      #10
                                      Re: Sont KDL42EX440 power supply

                                      Reporting that replacement of the main board restored full functionality to this set.

                                      Thanks to all!

                                        Comment

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