LG 50PA5500 Plasma - No picture then no sound

[Mac 108]

I was given a LG 50PA5500 50" Plasma that I am trying to bring back to life.

I was told that the picture went out first, then at some point later the sound went out too. I took off the back panel, but did not notice any obvious damage. This is my first television repair, so I don't know where to go from here.

The TV does click once when you press the power button, and the red light does come on, but there is still no sound or picture.

Here are pics:

[tom66]

Re: LG 50PA5500 Plasma - No picture then no sound

Having dealt with one of these myself...

Disconnect the top Y-buffer board. It's the board in the top left of the panel with the orange ribbons coming out of it. You will need to undo the ribbons and unscrew the board, then slide the board out from the connectors.

Turn the TV on, if you get half a picture, the plasma panel is bad and this is an unrepairable fault. There is a serious design flaw with these panels where the casing eats into the ribbons going to the panel causing short circuits. Unfortunately the ribbons aren't replaceable, they are glued to the panel.

[freakaftr8]

Re: LG 50PA5500 Plasma - No picture then no sound

Agreed. I sure hope it's not the dreaded ribbon cable crack! Everyone who has the pa5500 or pa6500 should file down that plastic tab just to make sure it doesn't happen to them. I've now seen four other sets here with the same issue. Sadly I have not been able to retain a ribbon cable yet to try to repair this. If possible of course. The outcome most likely will not be desirable.

[Mac 108]

Re: LG 50PA5500 Plasma - No picture then no sound

What is the proper way to disconnect the ribbons? They do not seem to want to move.

[tom66]

Re: LG 50PA5500 Plasma - No picture then no sound

You need to lift up the little latch next to each of them carefully, be careful not to damage the ribbons as they cannot be replaced.

[Mac 108]

Re: LG 50PA5500 Plasma - No picture then no sound

Ok, so I flipped the black latches, now what do I do? Do the tan pieces pop or slide off the board? Do the ribbons slide out of the tan pieces? I have never done this before, so I am trying to not to take any chances.

[tom66]

Re: LG 50PA5500 Plasma - No picture then no sound

With a small amount of force, they (the tan/orange ribbon) will slide out. There's a little bit of retention you will have to get over.

[Mac 108]

Re: LG 50PA5500 Plasma - No picture then no sound

Ok, I removed the upper left board and tried it again. I have the same symptoms. There is no picture at all. The TV clicks when you turn it on, the red light comes on, but when you press any of the other buttons, such as channel up, the set clicks off.

[tom66]

Re: LG 50PA5500 Plasma - No picture then no sound

Just to make sure, you unplugged the Y-buffer from the Y-sustain board?

[Mac 108]

Re: LG 50PA5500 Plasma - No picture then no sound

I'm not sure which those are. TV is at work. I'll post pics in the morning of exactly what I did.

Thanks for the help so far.

[Mac 108]

Re: LG 50PA5500 Plasma - No picture then no sound

Here's the board I removed:

[tom66]

Re: LG 50PA5500 Plasma - No picture then no sound

Good. That is what was needed, thanks for that.

Do you have a digital multimeter available?

[Mac 108]

Re: LG 50PA5500 Plasma - No picture then no sound

I do. I have a Velleman DVM890F. http://www.vellemanusa.com/products/...=enu&id=521426

[tom66]

Re: LG 50PA5500 Plasma - No picture then no sound

OK, using it, test the Vs and Va voltages on the power supply. These are usually available on test points. The multimeter needs to be set to the highest DC range available (usually 600 or 1000V.) For convenience, you can attach the black probe to the chassis. For now, leave the top buffer board out of the set.

[Mac 108]

Re: LG 50PA5500 Plasma - No picture then no sound

With the TV off, Vs reads 014 and Va reads 008. When the TV is on, it reads nothing. I had it set to 1000v.

[tom66]

Re: LG 50PA5500 Plasma - No picture then no sound

Ok, now remove the connection between the power board and Y-sustain board; the Y-sustain is the large left hand board.

[Mac 108]

Re: LG 50PA5500 Plasma - No picture then no sound

With the Y-sustain board disconnected and the TV off, Vs 002 Va 008.

[freakaftr8]

Re: LG 50PA5500 Plasma - No picture then no sound

Check the fuse above the two yellow transformers on the power supply with an ohm meter. If it's open that's your problem

[Mac 108]

Re: LG 50PA5500 Plasma - No picture then no sound

Fuse tests good

[tom66]

Re: LG 50PA5500 Plasma - No picture then no sound

Ok, now try with the Z-sustain out... by the way, are you turning the TV on (taking it out of standby)?