LG Plasma TV Model No. 50PJ550

[baggjn]

FAULT
Top third of picture hazy across full screen plus black patches that dissolve to nothing only to reappear depending on the brightness/darkness of picture. The haze symptoms remains at all times the TV is on. Any assistance would be appreciated, thanks.

[sordids999]

Re: LG Plasma TV Model No. 50PJ550

possible picture of the fault ?
Posting pictures of the back of your tv showing the boards with clear pictures may help you more with fixing your problem

[baggjn]

Re: LG Plasma TV Model No. 50PJ550

Thanks but the TV is wall mounted, I will have to wait for help to get it down, hope to re-post pics., a.s.a.p

[mmartell]

Re: LG Plasma TV Model No. 50PJ550

Post a picture of the fault first then, before you take the panel down.

[baggjn]

Re: LG Plasma TV Model No. 50PJ550

Where do I look to upload pics, please

[baggjn]

Re: LG Plasma TV Model No. 50PJ550

Hope these pics are helpful, Thanks

[Alastair E]

Re: LG Plasma TV Model No. 50PJ550

Check Vs, Va and particularly VSc Vy and VZBias....

Ive got one of these rotten abortions, Keeps blowing SUS-Up and SUS-Dn IGBT's after say 10 minutes of otherwise perfect operation, in my case, I'm suspecting the panel itself but one thing I did notice--wrong VSc and Vy will give the effect you have....

[baggjn]

Re: LG Plasma TV Model No. 50PJ550

Thanks for your reply however I am not very technical minded, I know basics and feel confident I could do an exchange board/panel without blowing myself up. I have clearer pics of what the trouble really looks like, I need to know what board I need to change that may cure the problem. Any help would be appreciated.

[Alastair E]

Re: LG Plasma TV Model No. 50PJ550

Does that black patch ever display picture or is it always like that?

I'm thinking that the fault would be on your Y-SUS board, if that patch shows picture sometimes--Same board I have a problem with, but at least yours doesnt blow up!

[baggjn]

Re: LG Plasma TV Model No. 50PJ550

Alastair, the patch dissolves very much like clouds as the sun warms them, they do reappear as quick as they go and the process starts again.

[tom66]

Re: LG Plasma TV Model No. 50PJ550

I would suggest Z-sustain fault.

[Alastair E]

Re: LG Plasma TV Model No. 50PJ550

Really Tom....?

It Looks a bit bright and fair contrast for an X-fault to me....

[tom66]

Re: LG Plasma TV Model No. 50PJ550

Really Tom....?

It Looks a bit bright and fair contrast for an X-fault to me....

I only suggest it, because I've seen similar on Samsung panels. The Z-output is working, but the Z-bias is missing for some reason. Some panels will even run ok without Z-bias, if Vsus is turned way up. Image may look a little fuzzy. Think freakaftr8 was playing with one doing that...

[freakaftr8]

Re: LG Plasma TV Model No. 50PJ550

ok on my TV Tom where the problem resided I found that it was the Ysus all along. In a fit of a hurry what I did was swapped out the bad Ysus with the same bad y sustain due to the fact that my kids were driving me crazy at the time and I wasn't paying attention I had both boards together. Turns out that on the Ysus I had no vsch control and the problem was intermittent. I figured this out by taking the bad board and putting it into the good TV and the same problem resided on that TV also. Still looking into why I have no vsch control but I can no longer rule out the Y sustain as a problem when I see a picture like this.

[tom66]

Re: LG Plasma TV Model No. 50PJ550

Interesting. Maybe best to check Vsc (same as Vsch on Samsung; -Vy is Vsc on Samsung...) and Vzbias to see if any are low. I would generally have thought Vsch failure would cause all lines on panel to be addressed (same as when the earlier LG buffers would short):

[freakaftr8]

Re: LG Plasma TV Model No. 50PJ550

that is exactly what I thought as well but I have 39 volts on vsch on the bad board which doesn't matter where I put the potentiometer stays at 39 Volts. on the good board if I turn vsch clockwise or counterclockwise I start getting these black blobs on the screen along with a whole ton of mal discharge

[tom66]

Re: LG Plasma TV Model No. 50PJ550

Did you measure Vsch to -Vsc? It is floating on top of -Vsc point, IIRC.

[freakaftr8]

Re: LG Plasma TV Model No. 50PJ550

Good point. I was checking vseh to ground. I'll check and update my original posting a little later

[baggjn]

Re: LG Plasma TV Model No. 50PJ550

I have been informed on another forum that my problem is on the Main Logic Board, not sure if the Z- board is the same one you guys are meaning, what do you think?

[MagicSmoke]

Re: LG Plasma TV Model No. 50PJ550

Service manual for tv here http://www.scribd.com/doc/98218930/S...Service-Manual

I have a Sanyo 50" that uses a Samsung panel and boards that was having similar issues with picture, see video here https://www.youtube.com/watch?v=xSewl8OINrA

Turned out to be a bad cap on X or Z board, a 680uf 35v. The only low voltage cap on that board. After changing cap video https://www.youtube.com/watch?v=mB9i...ature=youtu.be