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Sont KDL42EX440 power supply

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    #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
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    #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.

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      #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.

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        #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.

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          #5
          Re: Sont KDL42EX440 power supply

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

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            #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.

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              #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.

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                #8
                Re: Sont KDL42EX440 power supply

                ZY100110A is on the sticker on the main board.

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                  #9
                  Re: Sont KDL42EX440 power supply

                  Here are the two labels on the board.
                  Attached Files

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                    #10
                    Re: Sont KDL42EX440 power supply

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

                    Thanks to all!

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