50" LG Plasma-couple of (hopefully minor) problems

[d-animator]

I have a 50" lg plasma model no. 50ps3000-zb which was manufactured July 2009 and has a couple of problems. There's what looks like red/green and blue snow across the whole screen which is currently not very noticeable; when sat back from it it is not even visible and can only be seen when up close.

The second problem is very faint white lines that seem almost ghost like which move up the screen and again are not really noticeable except when the screen goes dark during a programme/movie. As it stands I could probably (begrudgingly) put up with it as it is but I'm really concerned that it may get worse. I have been unable to find any other posts with these same symptoms and would greatly appreciate any advice/suggestions?

P.S. I could try taking pictures of the problems if it helps, though I'm doubtful as to whether anything would show on the pictures.

[tom66]

Re: 50" LG Plasma-couple of (hopefully minor) problems

This is probably a SETUP/SETDN problem (controls on the Y-sus board), or a problem with the Vzbias, Vsc or -Vy voltages. We will need pictures of the chassis to give you ideas on where to look.

[d-animator]

Re: 50" LG Plasma-couple of (hopefully minor) problems

Ok great, thanks for the very swift reply, I'll post them asap.

[d-animator]

Re: 50" LG Plasma-couple of (hopefully minor) problems

Thanks Tom66 I really appreciate this, I should probably point out that I'm a complete novice with tv's (though not altogether tech' illiterate) but I'm a fast learner and fairly handy when it comes to taking things apart and putting them back together, also worked on many pc's and am well versed in the 'trial and error' technique

Apologies for not posting the pic's in the original post.

[tom66]

Re: 50" LG Plasma-couple of (hopefully minor) problems

OK -- in the red region you have the SETUP pot (the little screw-adjustment.)
Can't see a SETDN pot but it should be somewhere in the yellow area.

You want to try adjusting SETDN first. Try to get rid of the red/green/blue sparklies. Mark factory preset with marker pen. Power must be on during the adjustment and TV should display video. It's a good idea to use an insulated screw driver to make the changes. If you can't quite get rid of all of the sparklies find the minimum point and then adjust SETUP. Also, note SETUP controls the black level, so for deeper black level (higher contrast) you can adjust that control.

[d-animator]

Re: 50" LG Plasma-couple of (hopefully minor) problems

Awesome I'll try that, thanks your help is very much appreciated. I'm busy for the rest of the day but I'll try it out tomorrow and shall post my progress. Thanks again.

[d-animator]

Re: 50" LG Plasma-couple of (hopefully minor) problems

Ok so I tried adjusting the SETDN which was very interesting! at one end of the spectrum was the white-ish snow like picture which I've seen as a problem that a lot of people seem to suffer from and the other end or slightly before was the best picture I could get (actually not at all far from the factory setting). It is slightly better (and it wasn't really too noticeable in the first place) but despite adjusting the SETUP and playing with the contrast levels I have been unable to remove it altogether. Does this mean that I may need to (if it gets worse) replace the Y-sus board? I may be being naive but it doesn't look too difficult a job?

[tom66]

Re: 50" LG Plasma-couple of (hopefully minor) problems

I'd first try looking for a -Vy and Vsc test point. These may be them.

-Vy should be -180V
Vscan should be +140V

Check if these are so.
For -Vy you need to put red and black on the points I indicated.
For Vscan you can check with red lead on test point, black on chassis.

Set DMM to 200VDC.

[craig417]

Re: 50" LG Plasma-couple of (hopefully minor) problems

I have made repairs to a few off these TV's with the red sparkles on them. I have bought a few repair kits to fix this from ebay.
http://www.ebay.co.uk/itm/LG-50PS300...item4169df3fe3
This is the kit I have bought but usually ask for them without the capacitors for control board as I find that it is ok and not needing touched.
This kit also fixes a problem with the tv when it does not come on and just clicks. Usual sign the is the small square resistor has blown. Hope this helps.

[tom66]

Re: 50" LG Plasma-couple of (hopefully minor) problems

I thought that was for pink tinted screen? i.e. Z-sus failure? I was operating under the impression that it was a sparklies problem. Then again I haven't seen a picture of the fault.

[craig417]

Re: 50" LG Plasma-couple of (hopefully minor) problems

That's true a picture of the problem may be of help. Just the way I read it that's what I took his problem to be the red/green snow on the pic mostly only noticeable on lighter/white background. This is what I was thinking about in picture attached

[tom66]

Re: 50" LG Plasma-couple of (hopefully minor) problems

I'm surprised the Z-sustain can cause that. I haven't worked on any newer LG plasmas though...

[d-animator]

Re: 50" LG Plasma-couple of (hopefully minor) problems

Thanks for the responses, not sure what the problem is now. It is actually a lot more noticeable on dark backgrounds rather than white/light...

The dots do not seem to be overly red though it could definately be described as poor picture quality. I've struggled to get the problem to show on any pictures so I've taken a collection of photo's of differing scenes and types of image in the hope that you'll be able to discern the problem. Thanks so much for this it really is appreciated.

[d-animator]

Re: 50" LG Plasma-couple of (hopefully minor) problems

It doesn't seem to have a pink tint... in the 1st image you can see the whiteish ghost like horizontal lines that can sometimes be seen moving up the screen but these can only be seen on dark scenes the other problem can only be seen very close up and then again are more noticeable on the darker scenes. I don't have my multimeter with me at the mo so can't check the voltage but will get it tomorrow and will check that then.

[tom66]

Re: 50" LG Plasma-couple of (hopefully minor) problems

So this looks to me like maldischarge which is caused by Vscan, -Vy, SetUP and SetDN; please test the points I indicated.

[d-animator]

Re: 50" LG Plasma-couple of (hopefully minor) problems

Ok thanks I will do so tomorrow and post my progress.

[d-animator]

Re: 50" LG Plasma-couple of (hopefully minor) problems

Hmm now I'm fairly new to this side of things so I'm not entirely sure I'm doing this right, I think I've followed the instructions correctly; the Vy came out as -179.8, so far so good I thought, now the Vscan reads +43.3 and not +140!

[tom66]

Re: 50" LG Plasma-couple of (hopefully minor) problems

Yeah, that Vscan sounds like your problem... do you see an adjustment point?

[d-animator]

Re: 50" LG Plasma-couple of (hopefully minor) problems

Not sure. There's an adjustment screw nearby but it's not labelled very clearly. What do you think?

[tom66]

Re: 50" LG Plasma-couple of (hopefully minor) problems

Panel alignments manual:
http://www.tgohome.com/ServiceManual...&Search=Submit
(page 122)

That does appear to be Vsc(an) control.

However I may have got the Vsc measurement wrong. See the diagram for where to test. Please do not adjust until you have verified Vsc.