Vizio VT420M No Back Light

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  • budro
    Member
    • Mar 2012
    • 17
    • USA
    #1

    Vizio VT420M No Back Light

    I have a Vizio VT420M that has the orange vizio light when turned on and no backlight. Here are the voltages reading on the power supply/main board connector CN9102.

    OFF:
    o/f-.001
    PDIM-.000
    12vdc-.072
    12vdc-.072
    GND-0
    GND-0
    GND-0
    24vdc-.006
    24vdc-.006
    PS_ON-0
    5vdc-5.14
    5vdc-5.14

    ON
    o/f-.095
    PDIM-3.641
    12vdc-11.43
    12vdc-11.43
    GND-0
    GND-0
    GND-0
    24vdc-23.30
    24vdc-23.30
    PS_ON-4.99
    5vdc-5.12
    5vdc-5.12

    I have tried to short the 5v line to the o/f pin with the main board pin disconnected with a 1k resistor and no luck getting the back light to turn on. The o/f pin end of the resistor shows 1.44vdc with it connected to the o/f pin and disconnected shows just under 5vdc. almost like something is drawing it down. Anyone have any suggestions of what to try? I am leading to the main board but am open to ideas. Thanks in advance.
    Attached Files
    Tags: None
    • budm
      Badcaps Legend
      • Feb 2010
      • 40746
      • USA
      #2
      Re: Vizio VT420M No Back Light

      How about the pictures of the whole back side of the TV to see how all the boards are connected together?
      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

        • budro
          Member
          • Mar 2012
          • 17
          • USA
          #3
          Re: Vizio VT420M No Back Light

          Pic of the back
          Attached Files

            Comment

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