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Samsung pn50a510p3f, let's see if I learned anything....

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    Samsung pn50a510p3f, let's see if I learned anything....

    So today I gave $15.00 for a Samsung pn50a510p3f with the power cord, near brand new Samsung remote and the original owner's manual in the original bag.

    Report: Watching the super bowl, picture suddenly went out. Previous owner said he believed it was the y-sustain.

    Symptoms: Turns on, jingle seems a bit short. No backlights or picture on the screen. Sound unknown.

    So here's where we find out if I am learning anything:

    Just opened up the back of it. Check fuses. Y-sus fuse blown. Unit powers up and green light on logic board flashes about once per second.

    Unplug unit, use a bread tie and jumper Y-sus fuse. Measure Vs to ground, direct short, Va to ground infinite.

    Conclusion: Y-sus board has a direct short in Vs circuit and/or Y-buf is shorted explaining seller's symptoms.

    So, am I learning anything?

    Oh and the 75ohm in is broken off at the base. I think that was me......oops
    They call me......."threadkiller"

    #2
    Re: Samsung pn50a510p3f, let's see if I learned anything....

    Y buffers will not cause the fuse to blow, unless y sus took the brunt of a buffer failure. I would check for shorted mosfets on the y sustain to start.
    Did I leave the soldering iron on?

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      #3
      Re: Samsung pn50a510p3f, let's see if I learned anything....

      Okay so here's what I did:

      Y-buf quick test: One probe on Y-sus connector pin, the other ran over the terminals to the display. No direct shorts.

      Y-sus test: Ground probe to ground (circled in Yeller). Touch collector gate and emitter with the positive probe on the fets under the heat sink outlined in yellow and all indicate short to ground, or very close. Other fets on the board do not do that.

      So I'm thinking at least one of the fets under that heat sink has to be shorted to ground and because its in-circuit, all of them will indicate shorted?
      Attached Files
      They call me......."threadkiller"

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        #4
        Re: Samsung pn50a510p3f, let's see if I learned anything....

        That is correct. Usually rule of thumb is to replace all ones that read shorted. Even if the others were not in that same bank. Also there could be a chance that a gate drive IC has been damaged.
        Last edited by freakaftr8; 03-05-2018, 11:28 PM.
        Did I leave the soldering iron on?

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          #5
          Re: Samsung pn50a510p3f, let's see if I learned anything....

          Originally posted by freakaftr8 View Post
          That is correct. Usually rule of thumb is to replace all ones that read shorted. Even if the others were not in that same bank. Also there could be a chance that a gate drive IC has been damaged.
          Is there a schematic that shows where that is and a way to test that?
          They call me......."threadkiller"

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            #6
            Re: Samsung pn50a510p3f, let's see if I learned anything....

            There probably is but I dont have one. you would remove all components on that rail starting with designator "Q" , as there shorted, causing your blown fuse. Use diode mode on your DMM.
            Did I leave the soldering iron on?

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              #7
              Re: Samsung pn50a510p3f, let's see if I learned anything....

              So I pulled the Y-sus board and checked it out some more. Looks like Resistors R5117 and R5118 are open and Diode D5040 passes current both ways. Looks like the damage is a bit more extensive.....

              Can anyone tell me where the gate driver IC is and if it can be checked with a DVOM?
              Attached Files
              They call me......."threadkiller"

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