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Help diagnose no power on Changhong board

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    Help diagnose no power on Changhong board

    Hi forum friends,

    Got this Changhong power supply board model no.715G6503-P03-011-001C to tinker around. It was the power supply board for a defective Philips 200V4Q lcd monitor. The monitor was long gone disposed and i was given this board. The problem is there is no 19vdc output on the connector CN902.

    Fyi, i had checked all the diodes they are not open or shorted. The fuse is good as well as the coils. All electrolytic caps tested off circuit within 5% range capacitance and esr good.
    My suspect is on the 12 pin chip at U901 which is marked LNK6766V. I will attach the datasheet later.
    Attached now the image of the board top and bottom view.
    Attached Files

    #2
    Re: Help diagnose no power on Changhong board

    Hi forum friends,

    Attached the datasheet for the 12 pin chip LNK6766V (switcher?)
    Sorry that i do not understand well the datasheet and how to read it to help in diagnose if there is any problem on this chip. That is why i can only turn to this forum and request for any kind generous person to guide me step by step to revive the board if possible. I noticed that pin 5 does not exist on the board.

    Thanking in advance. Any help is much appreciated.
    Attached Files

    Comment


      #3
      Re: Help diagnose no power on Changhong board

      So c910 running cap in the hot side checked out OK for sure?
      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


        #4
        Re: Help diagnose no power on Changhong board

        Also "carefully" check the voltage ACROSS C910, it should be close to 6vdc

        Comment


          #5
          Re: Help diagnose no power on Changhong board

          budm,

          C910 being the running cap is Elite brand cap of 10uf 50v, it measured off board 9449nF and esr at 0.75 ohm. I compared other Sancon cap brand esr is at 1.4 ohm (new). So i guessed c910 should checked ok.

          R_J,

          I measured with Dmm at C910 while power on ac mains, but sadly there is no dc voltage.
          Got no voltage on other caps such as at c904, c801 and c906. Still no 19vdc at output connector.

          Comment


            #6
            Re: Help diagnose no power on Changhong board

            The ic will produce the startup voltage which should be on C910, I suspect the ic itself is bad. Check the components around the ic, if they are all ok there is not much else that can cause the problem.

            Comment


              #7
              Re: Help diagnose no power on Changhong board

              Hi forum friends,

              Thank you for the replies and I will take note to get the 12 pin ic LNK6766v on my next order.

              Comment

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