LG 42LH3000-ZA bad picture

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  • blaster_
    Member
    • Jan 2015
    • 15
    • Portugal

    #1

    LG 42LH3000-ZA bad picture

    Hi,

    My five year old LCD bought in late '09 (manufactured September '09) just started producing a really dark picture from a cold start after a couple of days without any use.
    The picture is dark in all inputs, menus and usb media player.



    Did the following with no results:
    mess with color options/wb
    factory reset
    messed around in the service menu tool options 1 (panel type) 3,4, WB, test pattern (only showed white)
    Updated firmware from 3.15 to 3.75 (service menu shorcut not working/altered?)
    swabbed with alcohol and resat t-con flat cables and connectors
    heat gunned as15-hf to try reflowing
    No change at all.

    Caps visually look ok. Everything looked clean and new for a five year old set. Just a couple of wires got loose from the tape holding them on the backplate. The t-con is an AUO ref T420HW04 V0 42T06-C03 barcode UZ-5542T06C16

    The picture isn't solarized/negative like in most faulty AS15, but I suspect this GAMMA chip. It has no thermal pads like the samsung models, no heat dissipation at all on the t-con. Just one chip on the main board and of course the bulky power board have heatsinks.

    Any idea besides getting a presumably new t-con over [fl]e[a]bay? Or toss it for a new one like the manufacturers want us to do? The resoldering of this tinny SMD is beyond my skill set, might try it later if a new t-con fixes the LCD. The chip on this board is AS15-HF, are AS15-F and AS15-G compatible?
    Attached Files
    Last edited by blaster_; 01-03-2015, 01:13 PM.
  • budm
    Badcaps Legend
    • Feb 2010
    • 40746
    • USA

    #2
    Re: LG 42LH3000-ZA bad picture

    t sure looks like bad Gamma voltages, you can take the reading of the Gamma voltages at the test point on the board and report the readings.
    You should match the PCBA P/N printed on the barcode and then go to shopjimmy.com
    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

    • blaster_
      Member
      • Jan 2015
      • 15
      • Portugal

      #3
      Re: LG 42LH3000-ZA bad picture

      Thanks for the help.
      I got a "new board" on ebay from a seller shipping from the US which has sold a ton of these. Although the serial number wasn't an exact match it fixed the LCD. The flat cable from the mainboard had to be pushed a bit harder than with the original t-con.
      My serial was: UZ-5542T06C16, "new board" is TZ-5542T06C12.

      From this experience I would say that as long as the ref T420HW04 V0 42T06-C03 matches between boards, the serial number (on barcode label) besides 42T06 doesn't matter.

      Anyone tried to put a heatsink on this chip to prevent it from going bad? Or are voltage spikes from line power the origin of the problem? Maybe a UPS with voltage normalization could help?

      Comment

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