BN44-00780A Blown Fuse - Troubleshooting

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  • Louis82
    Badcaps Veteran
    • Feb 2012
    • 240
    • USA
    #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
    Tags: None
    • budm
      Badcaps Legend
      • Feb 2010
      • 40746
      • USA
      #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

        • Louis82
          Badcaps Veteran
          • Feb 2012
          • 240
          • USA
          #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

            • Louis82
              Badcaps Veteran
              • Feb 2012
              • 240
              • USA
              #4
              Re: BN44-00780A Blown Fuse - Troubleshooting

              Photos attached
              Attached Files

                Comment

                • Louis82
                  Badcaps Veteran
                  • Feb 2012
                  • 240
                  • USA
                  #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

                    • maxvalutech
                      Badcaps Veteran
                      • Dec 2014
                      • 804
                      • australia
                      #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

                        • Louis82
                          Badcaps Veteran
                          • Feb 2012
                          • 240
                          • USA
                          #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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