Question about LG 42LC2D 42 in. LCD HDTV

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Hello i have an LG 50PG6010 and the screen is completely black, i have check the capacitors inside and the voltage from the power board, everything looks ok, what board should be faulty for me to replaced ,or there is something else i can try ? Thanks

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  • RUI MOREIRA
    RUI MOREIRA Sep 13, 2010

    THANK YOU VERY MUCH , IF THIS DONT HELP WHAT SHOULD HELP :)
    THANKS ..YOU ARE A GURU...;)

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  • LG Master
  • 5,054 Answers

First check your inverter. If your multimeter can read high frequency signals (~50 kHz), hold the probes about an inch above the inverter and a fraction of an inch apart. If you see a 1 or an actual value, you have a good inverter. If you see a reading near 0, the board is bad or the multimeter can't resolve the frequency. You can use an oscilloscope instead.

The backlight is another suspect part. This failure usually shows up as a gradual fading of the brightness or the on-screen image change to pink/red. With a bad backlight, you'll usually see a very dim image if you look at the TV from an inch from the screen. Block the room light from overwhelming this image (sometimes a carefully positioned flashlight will help you see something).

In some cases the video board might also fail.

In either case, you can buy a replacement inverter for $50-150 and just do a simple swap. Disconnect all of the wires (connections are similar to molex and ribbon cables in a computer) and remove board (a few screws usually). Connect the cables to the new inverter. (If you google backlight inverter replacement, you'll find videos and text descriptions.) Note the part number on the board, including the Rev number, and order the exact one (shopjimmy.com or lcdparts.net are good starting points). Universal inverters do exist but can result in reversed controls (up to lower the brightness). Replacing individual parts on the board is cheaper but more prone to not tracking down all of the bad parts.

If the inverter is good, then it's probably backlights themselves (several in most TVs). These are sandwiched on the perimeter of the TV (usually under some tape that holds the lamp, reflector and other parts together. You need to order by length and width and get ones for your TV size. Remove the tape, and separate the reflector (make a note of how things are put together) then you have to Dremel (or use another rotary tool) to remove the plastic to get the backlight out. (They are often molded into the frame.) Then put in the new backlight and reassemble everything. (http://www.lcdparts.net/howto/default.aspx) but for an overview: http://www.inventgeek.com/Projects/BacklightFix/overview.aspx Then push the new backlights into place, reconnect the wires and close up the sandwich of tape and other parts around the screen. Then replace it in the bezel.

With a good spare backlight, you can test an inverter for condition (plug together and turn on the tv while the box is open). Similarly a good inverter can test the backlight.

I hope this helps.

Cindy Wells

Posted on Sep 13, 2010

  • Cindy Wells Sep 13, 2010

    You're welcome. The inverter failure is the most common. The video board usually only fails if a surge hit the unit (and then losing the power supply or the inputs are more likely). The backlights fail at the same rate as most fluorescent tubes - rarely but you usually see it coming.

    If these don't help, the next solutions depend on how you fixed the problem. If you replaced the whole boards, then you need to check if the new boards are good and the cables. If you were replacing just bad parts or resoldering bad connections, check if you missed a problem, shorted across the board or missed a fuse/resistor/zener diode that was blown.

    I hope this helps.

    Cindy Wells

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