Sharp LC-42SB45U No Picture, Sound or Response to Button Presses

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  • Syryll
    Member
    • Jul 2012
    • 32
    • United States

    #1

    Sharp LC-42SB45U No Picture, Sound or Response to Button Presses

    Yet another dead TV I picked up to play with. As soon as I apply power to the set, I get a green light with a single flash, and then solid. I can't power the set off or anything.

    As far as the connector from PS to the mainboard, these are the readings I get:
    CN902
    5v: 5.11v
    PS_ON: 1.77v
    12v: 12.11v
    24v: 24.21v
    BL_ON: 0.06v
    As per other posts, I've tested F1, F2 and F3 on the inverter board. All tested fine.
    Attached Files
  • budm
    Badcaps Legend
    • Feb 2010
    • 40746
    • USA

    #2
    Re: Sharp LC-42SB45U No Picture, Sound or Response to Button Presses

    You all the correct Voltages except you do not have BL-0N signal from the main board to turn on the backlights circuit. So you have main baord problem.
    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

    • Syryll
      Member
      • Jul 2012
      • 32
      • United States

      #3
      Re: Sharp LC-42SB45U No Picture, Sound or Response to Button Presses

      That's what I figured. Thanks!

      Comment

      • Syryll
        Member
        • Jul 2012
        • 32
        • United States

        #4
        Re: Sharp LC-42SB45U No Picture, Sound or Response to Button Presses

        I decided to check the panel for cracks and backlight prior to ordering a mainboard. I've got 5v jumped to PS_ON and BL_ON with separate 1k resistors, and I just get backlight for about a quarter of a second when I plug the set in. Do I have to have something on the brightness pin as well, or is something else afoot?

        Comment

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA

          #5
          Re: Sharp LC-42SB45U No Picture, Sound or Response to Button Presses

          When you do the force on using resistors, you MUST remove the cable going back to the main board first, we do not want to back feed the force signal back to the main board.
          There should be another pin for dimming control that may need to have the resistor connected as well.
          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

          • Syryll
            Member
            • Jul 2012
            • 32
            • United States

            #6
            Re: Sharp LC-42SB45U No Picture, Sound or Response to Button Presses

            Yup, it's disconnected from the mainboard. It does have a brightness control pin. It's pin 2 on CN902. How would I go about adding that pin to the jumper? Just add another 1k or so resistor from 5v to that pin?

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA

              #7
              Re: Sharp LC-42SB45U No Picture, Sound or Response to Button Presses

              Originally posted by Syryll
              Yup, it's disconnected from the mainboard. It does have a brightness control pin. It's pin 2 on CN902. How would I go about adding that pin to the jumper? Just add another 1k or so resistor from 5v to that pin?
              Yes.
              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

              • Syryll
                Member
                • Jul 2012
                • 32
                • United States

                #8
                Re: Sharp LC-42SB45U No Picture, Sound or Response to Button Presses

                Same results. 1/4 of a second flash then off the backlight goes. I checked 5v, 12v, and 24v to make sure they weren't falling out. They're all steady at their respective voltages.
                Last edited by Syryll; 09-04-2015, 11:53 PM.

                Comment

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