Inverter shuts down instantly

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  • mancaveman
    New Member
    • Aug 2012
    • 8
    • Hungary

    #1

    Inverter shuts down instantly

    Hey guys

    I'm kind of at my wits end with this repair. I'm wondering if anyone could maybe offer some advice.

    Subject: DARFON 4H.V1561.091 4-channel backlight inverter

    Symptoms:
    Instant shutdown with any tube connected to CH4 (barely noticeable blink)
    With no tube on CH4 runs all other channels for 2 seconds then shuts down
    Does the same with known-good tubes.
    Known-good inverter does not shut down with the tubes that go with this board.

    Fuse is intact.
    Transformer primary and secondary resistances
    4: S:1067 P:0.7
    3: S:1067 P:0.68
    2: S:1077 P:0.7
    1: S:1067 P:0.7
    Swapped the CH4 transformer for one of the others anyway, same result.
    Gate-Source-Drain resistances on the driver FETs are consistent between channels.
    The two lytics on the board are Rubycon but I measured them anyway. They're fine for both ESR and capacity.
    All resistors on the board measure within tolerance.
    Just to make sure it's not the power supply I hooked wires up to it and powered it up from a battery. Same results.

    It seems that CH4 alone is used for something by the controller because it's the only one connected through at D12. Moving that diode down that row also moves the instant-shutdown fault to other channels. Removing the diode makes all channels work for 2 seconds.

    The controller is an LX6512.

    Any ideas?

    Thanks
    Attached Files
  • budm
    Badcaps Legend
    • Feb 2010
    • 40746
    • USA

    #2
    Re: Inverter shuts down instantly

    Did you check those ballast caps C25, 26 for any leakage resistance?
    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

    • mancaveman
      New Member
      • Aug 2012
      • 8
      • Hungary

      #3
      Re: Inverter shuts down instantly

      Just checked both. They measure fine out of circuit

      I can also change the channel that triggers the shutdown by changing the position of the diode in the D9-D12 row that selects between the channels for what I assume is some sort of feedback. (No idea why they only take it from a single channel though.)

      Comment

      • mancaveman
        New Member
        • Aug 2012
        • 8
        • Hungary

        #4
        Re: Inverter shuts down instantly

        Thanks for the reply though.

        Ended up being a bad controller chip. Replacement fixed it
        Last edited by mancaveman; 04-14-2014, 06:19 AM.

        Comment

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