Unknown issue with Panasonic LED TV.

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  • Mikeyboy2007
    Badcaps Veteran
    • Mar 2013
    • 745
    • Scotland

    #1

    Unknown issue with Panasonic LED TV.

    Hi guys, I have a Panasonic TX-46AS740B TV here with a TNPA6011 power supply. The issue i have is when you power tv on the green light flashes and tv trys to boot up, LED panel flashes 3 times around 2 seconds apart then red standby light starts flashing. I have stripped screen out of tv and can see that when the LED panel is trying to switch on the entire bottom row of LEDs is out. I have swapped the led strips about and also swapped with brand new working ones and still the same issue. Anybody have any ideas what is going on ?

    Help much appreciated, would be a good tv to just throw in the tip.
  • R_J
    Badcaps Legend
    • Jun 2012
    • 9535
    • Canada

    #2
    Re: Unknown issue with Panasonic LED TV.

    Check the voltages on P4 plug pins 2,4,6,8,10 & 12. Monitor the pin while turning on the tv and see if one of the pins is either very high or at 0 compaired to the others.
    If one pins it different, check that trace back to its transistor (IE: Q7806) and check the transistor and resistors (If Q7806, check R7851,R7881,R7882,R7802,R7864) (If Q7805, check R7850,R7879,R7882 etc.)
    There is a schematic online

    Comment

    • Mikeyboy2007
      Badcaps Veteran
      • Mar 2013
      • 745
      • Scotland

      #3
      Re: Unknown issue with Panasonic LED TV.

      Hi R_J thanks for reply. I checked pins 2,4,6,8,10 & 12.. as soon as you plug tv in it trys to boot up and pins 2,4,6,8 and 10 all around 7.5v then backlights fire up 2,4,6,8 all quickly spike to 24 before slowly dropping and pin 10 goes to 20v.. pin 12 has 0v at all so will check schematic and see what i can do. Im not too sure how to check a teansistor but google will be my friend today. And will also check out schematic.

      Comment

      • R_J
        Badcaps Legend
        • Jun 2012
        • 9535
        • Canada

        #4
        Re: Unknown issue with Panasonic LED TV.

        I would check the line between the power supply P4 pin 12 and the panel, It sure looks like an open led string or open connection somewhere.
        The led voltage is supplied by a common point P4, pin 1,3,5 etc. then the return of the led strings connect to p4. 2,4, 6 etc.

        Comment

        • Mikeyboy2007
          Badcaps Veteran
          • Mar 2013
          • 745
          • Scotland

          #5
          Re: Unknown issue with Panasonic LED TV.

          Had this one on hold as been away on holiday etc, but will check over the next few days and figure out whats going on and will update the thread.

          Comment

          • Mikeyboy2007
            Badcaps Veteran
            • Mar 2013
            • 745
            • Scotland

            #6
            Re: Unknown issue with Panasonic LED TV.

            Ok, so ordered another power supply, when it arrived it was fitted but backlights flashed with that one and still missing voltage on pin 12. Now what i did notice is on the postive / negative going to the LED steip thats out is a different coloured possibly burnt connector. Could this be causing the issue ?

            I have attached picture
            Attached Files

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA

              #7
              Re: Unknown issue with Panasonic LED TV.

              It looks like cold solder joints so you end up with bad contact resistant. I would clean it up and apply Flux & new solder, I would do all of them instead of waiting for others to fail later on.
              Last edited by budm; 06-27-2019, 05:35 PM.
              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

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