LG 50PA6500 Problem

[Twithers]

I picked up this LG plasma 50PA6500 with a suspected power problem. The previous owner said it would run for a few minutes and then turn itself off. Pretty typical for anyone who does this sort of thing regularly.

In actuality, when I get it home, it's doing something a bit different.

When I plug the power cord in, the set clicks once, flashes a bright screen (not white but bright backlighting) and then stays at a dim black screen, as if the backlighting is on but there is no image. The weird part is that I can't turn it off. Either with the remote or the hard button. The tv does not respond to any input and will not turn off without unplugging the power cord. There is no sort of startup indication, i.e. a jingle tone , menu image, channel indicator, nothing. Plug in the power cord, single click, bright momentary flash, then dim backlight, that's all.

I haven't opened it up yet, but I'm wondering if anyone has had this issue, especially not being able to turn it off. I've repaired many different types of TV's but never one I couldn't turn off. Strange!

Any ideas?

[Twithers]

Re: LG 50PA6500 Problem

I forgot to add that the power/standby light is solid red the entire time. no flashing at all.

[Twithers]

Re: LG 50PA6500 Problem

Update:

I have 205v on VS and 55v on VA.

I checked the board that has all the pushbuttons on it (I forget what it's called) and all the buttons seem to function properly.

I've gone through all the connections and made sure everything was seated well.

The buffer boards are functioning as you'd expect. Unplug and half the screen goes black and vice versa.

Nothing I've done changes the fact that I can't turn the set off without unplugging the cord.

I don't know if that is connected to the fact that there is no image on the screen or not.

I'm stumped. All the power circuits seem to working properly but I've made no improvement, or even change for that matter.

Anyone?

[Twithers]

Re: LG 50PA6500 Problem

Update:

I found another post that had a trick for troubleshooting that I tried.

I unplugged the ribbon cable that runs from the main board to the control board and I jumpered out the 2 test points.

The display start showing a test pattern. Full white screen, full red screen, full green screen, etc.

The post where I found the tip said that this result narrow down the problem to a faulty main board.

Has anyone done any repairs to a main board before?

[freakaftr8]

Re: LG 50PA6500 Problem

Could be an EEPROM issue. Also could be a faulty voltage regulator.

[Twithers]

Re: LG 50PA6500 Problem

Would there be any measurements that would point me to a voltage regulator? I seem to have all the different voltages I'm supposed to.

[freakaftr8]

Re: LG 50PA6500 Problem

Can you post a picture of the main board? What is PS on doing when you plug the TV in?

[Twithers]

Re: LG 50PA6500 Problem

I'm not sure what PS on is.

[freakaftr8]

Re: LG 50PA6500 Problem

Try heating up ic400 with a hairdryer a little and observe behavior. Also what's the DC voltage reading on IC604 off the big tab. Put black lead of volt meter on frame of tv.

[Twithers]

Re: LG 50PA6500 Problem

No change when I put my heat gun on IC400.

IC604 read 1.8vdc on the big tab.