LG 50PG6010. Blown PSU replaced, then No Picture.

[baddesley]

Hi Guys,

I have an LG 50PG6010 50" Plasma, which I have had for over a year now and which has worked fine for all that time (once I'd replaced the four 3300mf caps on the PSU anyway).

Recently though, it delveloped a fault with the PSU, failing to come on, but while trying to sort that out, the PSU blew up, taking the Y Sus with it.

Initially, I replaced the PSU, which now works fine, all voltages present and normal, but I got no picture (sound OK). It was then that I found out that the Y Sus was faulty (a couple of blown FETs and a SM fuse at least), but rather than replace these, I bought a tested replacement board from the same people that I'd got the PSU from.

However, despite it seeming to run OK (all fuses intact and all heatsinks running nicely warm, including those on the buffer boards), there is still no picture. The PSU runs quietly and the sound is fine. I tried to measure VY and VSC on the Y Sus board, but on DC 600V range (highest on my DMM), it goes off scale. Is this normal?

The X Sus heatsinks are cool though, despite power being on the board and all FETs/Transistors and Fuses checking out OK (cold checks with DVM), so to my mind, this is not being driven at all - though my knowledge of plasmas is very limited (I'm an old-school ex - CRT TV & general Electronics Engineer).

I have tried disconnecting the lower driver L & R boards, but no difference. Any ideas, as this is driving me nuts and I have not been able to get any circuit diagrams (downloaded the supposed service manual, but that has very limited low power only circuits).

Any advice, ideas, or full circuit diagrams would be much appreciated. Thanks in advance.

[baddesley]

Re: LG 50PG6010. Blown PSU replaced, then No Picture.

Anyone? Any idea how to check my X Sus, if this could be the problem, of any other ideas? Sorry for posting again, but I really do need some help on this.

[baddesley]

Re: LG 50PG6010. Blown PSU replaced, then No Picture.

OK, well I have now fixed this with a nex X Sustain board (or is it Z Sus?), so it seems that can indeed cause no picture, though I've no idea what on the board was causing this, as everything seemed to check out OK.

It would have been nice to have had some confidence in my decision before buying this though, as it's now cost me a fair bit in new panels. Not sure why I didn't get any replies to this (or either of my other posts!), maybe I've just been unlucky and asked questions about sets nobody knows much about.

[Caleb]

Re: LG 50PG6010. Blown PSU replaced, then No Picture.

glad to hear you got it fixed. some of these threads just don't get very many hits. tom has a very thorough post on how to diagnose plasma failures.

[baddesley]

Re: LG 50PG6010. Blown PSU replaced, then No Picture.

Thanks, I guess I've just been unlucky so far.

However, I've now got another problem with the TV; purple on some highlights and some sparkling, which I've seen mentioned on here before on other sets. I've carefully adjusted VS and VA on the power supply, but this has just made it a lot worse. If I adjust VS up from the stated 195V to 200V, the problem is a lot less noticeable, but obviously, I don't want to leave it like this and the picture's still not right anyway.

There are several adjustment pots on the Y Sus and one on the X Sus and I've tried gently 'rocking' these back and forward (and back again), but none make much, if any, difference. Obviously, I don't want to mess these up too much without having some way of measuring what I'm doing. Anyone have any info on setting these up?

The service manual (very limited!!) mentions a set-up menu, but I haven't found how to get into this, as some of the keys it mentions on the remote are simply not there (could be a special service remote?). Anyone with any info on this, or other ways to sort this out?

I have been very careful to get the correct version replacement boards, but these could need setting up/matching or could of course be faulty.

Anyone got any ideas?

[R_J]

Re: LG 50PG6010. Blown PSU replaced, then No Picture.

Those voltages are for a new panel, as the panel ages they may need to be adjusrted slightly, usually vs can be lowered by around 5volts and vsetup vsetdown can be adjusted for minimum speckles (the correct way is with a scope). but as the panel ages you can only do so much. Another thing is the control board may need new firmware (loaded on with a special jig) as for getting into the service menu, that wont help the speckles. and lg did use a special service remote.

[baddesley]

Re: LG 50PG6010. Blown PSU replaced, then No Picture.

Thanks RJ,

Any idea what a safe maximum is for VS, as increasing this helps (reducing makes it worse, even the standard 195V produces the sparkles/tint on highlights). Unfortunately, I've no idea what VS was before I replaced the power (and other boards) - when the picture was perfect!

[baddesley]

Re: LG 50PG6010. Blown PSU replaced, then No Picture.

This is what I'm getting, though it's difficult to get a good image of what is happening (i.e., its actually worse than these photos show):






This seems to be worse once the TV warms up. Has anyone got any idea what is causing this and what to adjust/replace to fix it? Is there a sequence to follow to adjust the various preset pots in the TV for instance (the picture was absolutely perfect before the Power boatd went and I had to replace this and the Y and X Sustain boards)? Thanks.

[tom66]

Re: LG 50PG6010. Blown PSU replaced, then No Picture.

Check the -Vy voltage on the Y-sustain and the Vzbias voltage on the Z-sustain.

Compare voltages to panel sticker. Order is:

N.A. / -Vy / Vsc / N.A. / Vzbias

or rarely:

N.A. / Vsc / -Vy / N.A. / Vzbias

(the minus sign tells you which is -Vy)

[baddesley]

Re: LG 50PG6010. Blown PSU replaced, then No Picture.

Thanks Tom, much appreciated, I'll have a go at that tomorrow. I did look for marked voltages before and couldn't find any, other than VS and VA, but I'll have another look tomorrow. Having a sequence should certainly help too.

[baddesley]

Re: LG 50PG6010. Blown PSU replaced, then No Picture.

OK, well I tried to check and adjust these volages, but unfortunately my DMM will not resolve the Vsc and -Vy voltages (shows out of range), presumably due to the high frequency component, but I was able to adjust the Vzbias correctly. The bare voltages were listed on the panel, but there was no reference to which voltages they were, which is why I was unable to check and adjust anything before!

However, none of these made much of a difference, only VS made any difference and I have solved the problem (as far as I can tell) by adjusting this up to 205V (TV well warmed up, showing high brightness picture). This is far from ideal, as its supposed to be 195V, but it seems to be the only thing that fixes it - unless anyone has any other suggestions.

Thanks for your help anyway Tom, it gave me the confidence that my Vsc, -Vy and Vzbias are near enough correct. I just hope the set is still reliable with it set like this!!

[baddesley]

Re: LG 50PG6010. Blown PSU replaced, then No Picture.

Unfortunately, not solved, but greatly improved; it only flares on a few high brightness/contrast scenes now. I am reluctant to increase VS further however, but if anyone else has any ideas, or can tell me what VS they have adjusted theirs to to solve this problem, they would be much appreciated. Otherwise, I think I'll leave it at that and put up with it for the sake of reliability. Thanks again to those that have helped.