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BN44-00780A Blown Fuse - Troubleshooting

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    #1

    BN44-00780A Blown Fuse - Troubleshooting

    Hello there.

    I have this curved samsung tv with power board BN44-00780A that has a blown fuse.

    I found a ceramic cap burned (CP814). Replaced them and now I get 3.3V Standby, 176V on filter cap but nothing else.

    I only brought the power board to my shop and I'm not sure if this power board needs from main board to fully activate or if I still have more problems since I'm not getting 450v on filter cap. Any thought?

    Here are the pins that have voltage:

    PS ON/OFF = 3.3v
    A5V = 5V

    Everything else is 0V

    Thank you.
    Attached Files
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    #2
    Re: BN44-00780A Blown Fuse - Troubleshooting

    It has PFC Voltage booster circuit so you should have around 380~400VDC on the main filter cap when PS-ON is present.
    I cannot see the CP814 in the PFC section. It sounds like one of those small blue disc snubber cap.
    Check Diode DP802, 803 to see if they have leakage resistance in both directions or not.
    Did you hear the relay RL802S clicks on?
    Never stop learning
    Basic LCD TV and Monitor troubleshooting guides.
    http://www.badcaps.net/forum/showthr...956#post305956

    Voltage Regulator (LDO) testing:
    http://www.badcaps.net/forum/showthr...999#post300999

    Inverter testing using old CFL:
    http://www.badcaps.net/forum/showthr...er+testing+cfl

    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
    http://s807.photobucket.com/user/budm/library/

    TV Factory reset codes listing:
    http://www.badcaps.net/forum/showthread.php?t=24809

    Comment

      #3
      Re: BN44-00780A Blown Fuse - Troubleshooting

      Hi Budm - No click on relay. How do I check for current leakage ?
      BTW, I also replaced QP802. It was shorted when removed from board. I forgot to say that on my first post. CP814 is in front of DP801C and next to QP802 (the one I replaced).
      Adding a photo of my board on next post.

      Comment

        #4
        Re: BN44-00780A Blown Fuse - Troubleshooting

        Photos attached
        Attached Files

        Comment

          #5
          Re: BN44-00780A Blown Fuse - Troubleshooting

          Ok Budm.
          I made a mistake of forgetting to put all blue caps back. If you see my picture I was missing CP815. However, I put it back and still same problem. Only 170V on Filter cap and no relay clicking.

          Comment

            #6
            Re: BN44-00780A Blown Fuse - Troubleshooting

            If as you say the PSU isn't connected to main then you will need to force pson to get other voltages up.

            Comment

              #7
              Re: BN44-00780A Blown Fuse - Troubleshooting

              Ok After 3hrs, It's Fixed.

              Issue was the IC loc ICP801. I removed a new one from a board I had, swapped it and it worked. Filter cap measures 450v same with LED driver out.
              Will provide update once board is installed on the TV.

              No I didn't need the main board to kick this circuit board on. Pull up resistor is there - Just learned that, Thanks Budm!

              Comment

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