LG Plasma 50PG100R Problem

[VHSFI]

Re: LG Plasma 50PG100R Problem

So if i get OL in diode test mode with the Red Lead on the Small copper strip and the Black Lead on the Bigger copper strip, so i should apply the + of the power supply to the small strip and - to the big one ?

[tom66]

Re: LG Plasma 50PG100R Problem

That sounds right - you want the chips to normally be blocking the current rather than letting it through.

Start with a lower voltage, 1-2V, and ramp it up slowly until the chip starts getting hot. It may be a good idea to remove those heatsinks too so you can easily see it.

[VHSFI]

Re: LG Plasma 50PG100R Problem

Update:

So did the experiment today it went rather well, started with a low voltage and slowly push it up to around 20v current went to about 350mA this for about 20sec was enought to see the culprit, top most IC on the top y-buffer started to get really hot all other IC's were cold, repeated with the other board and suprise surprise the exact same IC was bad too.
I then removed that IC from one of the boards, witch was a bitch to do due to all the glue they have in there and due to the IC having a solder pad on the bottom (broke one of the tracks in the process), doing the diode test after checked ok so i pluged the board in the tv and now the screen lights to about 5/6 of the screen all white with some garbage around, voltages on the Y-sus (VY - VSC) all good.
So this is starting to look like the panel went poof.
Might try to transplant one of the good ic's and see how it goes, but there doens't seem to be much hope for this one.

[tom66]

Re: LG Plasma 50PG100R Problem

Hmm, I hope it hasn't, but you may find it has failed

The TV just died, wasn't impacted or dropped or anything like that?

It is potentially possible that maybe the topmost IC is weaker to other failures?

[VHSFI]

Re: LG Plasma 50PG100R Problem

Yeah just died like that, one day finished watching tv turned it off, next day nothing.
Btw can the Z side of things have anything to do with this, there is another voltage on that sticker on the back of the panel think is 94V, on the Z board there is a marking Vza or Vzs can't remember now near a resistor prety much like the VY & VSC on the Y board but i doens't read any voltage when measuring across it also there are 2 big heatsinks on the Z board but only one seems to warm up.
Problems there too, or perhaps another indication of panel problems ?

[tom66]

Re: LG Plasma 50PG100R Problem

In general, no - the Z-sustain is only responsible for providing the second sustain drive. It alternates polarity with the Y-sustain to create the AC panel drive signal. If it goes bad you usually still get a picture, it's just very dim or purple tinted (due to insufficient discharge -- high UV content.)

With no picture, there's no plasma drive, so you wouldn't necessarily expect the heatsinks to warm up.

[VHSFI]

Re: LG Plasma 50PG100R Problem

The transplant operation didn't go so well, all that glue between the IC legs just make the solder procress very hard to do, i ordered some new ones should make the solder process a lot easier, meanwhile this is what i was able to get, well at least the screen gives coherent image the dead lines are surely due to soldering problems.

[tom66]

Re: LG Plasma 50PG100R Problem

Note now whether the Z-sustain heatsink gets hot.

It could also be a loose panel connector with the lines.

It's looking like it might just be that the top IC likes to fry first (maybe because it is turned on first when driving the screen?) You should contact the seller about the failed buffer and get a refund.

I think your panel is good then, I would expect failures are quite rare (after all, it requires a join be made between adjacent lines, which is unlikely.)

[VHSFI]

Re: LG Plasma 50PG100R Problem

Z-Sus is Ok
From what i read in a couple of parts sites it seems it's a common fault with some LG models including this one.
I'll make my final report as soon as i get the IC's. shouldn't take long to arrive.

[crashomatic]

Re: LG Plasma 50PG100R Problem

Gentleman,

I have a LG 50PG20-UA and I have no picture, sound is fine. Visual inspection shows no sign of trouble on the boards. If I remove the upper y-buff and I get the bottom half of the screen to go white, bright for a few seconds, then about half as bright. Upper y-buff back in and the screen gets nothing. Is this most likely a bad upper y-buff and is it worth ordering that card to see if it fixes it? Thanks.

[tom66]

Re: LG Plasma 50PG100R Problem

It is probably best to create a new thread as your problem is quite different.

[crashomatic]

Re: LG Plasma 50PG100R Problem

Will do.

[crashomatic]

Re: LG Plasma 50PG100R Problem

Alas, I cannot post new threads yet. I will start one when I have been authorized.

[tom66]

Re: LG Plasma 50PG100R Problem

You only need to post one post to start a thread I believe; that's typically the "new members" thread at the top of the forum.

[crashomatic]

Re: LG Plasma 50PG100R Problem

I thought I read that during sign up, but it is telling me I cannot start a new thread. (No permissions or not authorized.)

[kca]

Re: LG Plasma 50PG100R Problem

Hello VHSFI (or anyone else connected to this thread) ~

VHSFI ~~ Did you ever find a solution to your problem with this set?

I have a very similar issue with an LG 60PX950.

[rangaswami]

Re: LG Plasma 50PG100R Problem

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