LG 37LC7D - turns on for several seconds then goes grey

[frannyjunk]

Hi, I have an LG LCD TV that I am trying to diagnose. Here are the symtoms. I can turn in on no problems. After a random amount of time (sometimes a few seconds, sometimes hours), the screen goes dark grey (backlight still on, I can see it). I can unplug the ribbon cable from the power supply to the mainboard, then re-plug it in and the TV is ok upon turning on. After a few seconds (to sometimes minutes), there's a pop and the TV makes a faxing machine type sound (high pitch recurring whine). Can I assume that this is a mainboard issue? There is no sound outside of the high pitch whine. My logic:

TV turns on and off just fine = power supply is ok
TV comes on and works fine after everytime I unplug the power supply ribbon cable (not the 5V but the 12/24V) = TCON is ok

Is my logic correct? I don't know how to check the power supply to the mainboard. Perhaps someone can instruct me?

Thanks for any help the forum can provide. Thanks!!


P.s. I don't see any bulging caps.

[Hobby 1]

Re: LG 37LC7D - turns on for several seconds then goes grey

A bad T-con will give you a grey screen.
The power supply voltages will be labelled on the board. Measure the voltages when the set is on and working ok as well as when the problem shows up. See if there is any difference.