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SammyPN42 Has Audio/No Video

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    #1

    SammyPN42 Has Audio/No Video

    VS and VA both at 52V DC. I have all correct voltages at large connector on smps feeding main board except 5.3V pair in middle. I have 15V and 5 volt standby. PS_ON has 3.3 volts when off, 0V when on. I have 5.3V going to Logic Board from small connector on smps. I ?Do not have any voltage ever on VS_ON from Logic board to smps.
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    #2
    Re: SammyPN42 Has Audio/No Video

    It is obvious the logic board sends the VS_ON signal to SMPS. I assume that the MAIN board tells the logic board to do so..hard to isolate as the only connection between the two boards is a ribbon cable..can anyone tell me what voltage is supposed to be applied to VS_ON? Could the lack of 5.3V on the center two conductors in the cable from SMPS to Main be the cause of the lack of my VS_ON signal?
    Thanks In Advance!
    Last edited by ljintexas; 03-31-2018, 02:04 PM.

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      #3
      Re: SammyPN42 Has Audio/No Video

      VS_ON should be 3.3V according to what I have found and is switched by logic board. I have a board on the way..

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        #4
        Re: SammyPN42 Update

        Update: Replaced logic board and smps. Still have slow flash on LED on logic board.I now have 5.3V on two pins of cable going from smps to Main board.(Did not have before)
        I am now getting 3.2V for about 3 to 4 seconds from logic to VS_ON on smps, then drops to zero.
        With all boards plugged in, smps is going into shutdown of some kind. If I unplug Y sus cable I get start up with samsung jingle. If I plug y back in and unplug X main, I also get start up and samsung jingle..There are some stains on bottom side of X main..Could this be from water?
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          #5
          Re: SammyPN42 Has Audio/No Video

          Did you see my thread? https://www.badcaps.net/forum/showthread.php?t=67959

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            #6
            Re: SammyPN42 Has Audio/No Video

            I just read it. Very good information. In my case, three of the 5 transistors on X main are shorted. Looks like water may have contacted X Main..I tested Y buffer board for shorts and did not find any..I will try the ribbon cable test.
            Thanks for the info!!
            LJ

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              #7
              Re: SammyPN42 Has Audio/No Video

              Here is one X main repair kit. It has two IGBT transistors and also replaces an IC.

              https://www.ebay.ca/itm/Repair-Kit-F...-/221871091607

              Here is one Y main repair kit.

              http://www.shopjimmy.com/samsung-bn9...repair-kit.htm

              There is a note on Shopjimmy to update the firmware if the Xmain is replaced.

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                #8
                Re: SammyPN42 Has Audio/No Video

                Q4001, Q4003, and Q4007 IGBTs are all shorted on X Main.

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                  #9
                  Re: SammyPN42 Has Audio/No Video

                  Replaced X-Main. Same slow heartbeat on logic. Removed new X Main, same IGBTs are shorted. Y-Main has to be the culprit. With both X and Y sustains disconnected both cables and ribbons, I get a happy heartbeat on logic board. Retested Y buffer for shorts, none found.

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                    #10
                    Re: SammyPN42 Has Audio/No Video

                    Replaced shorted IGBTs on X Main Q4001 and Q4007. Replaced Y Main and Buffer..we have pictures!
                    Thanks to all.

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