Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

[richto]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

OK, will check Vsus later today when i'm home. Should be about 205V? Is that DC?

[tom66]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

It's probably different but worth verifying all voltages are correct. Looks like a bad SC board to me.

[richto]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

I have a similar but much more extreme picture issue after changing the SC board on a Panasonic TX-P50VT30B. The TV now powers up but the screen is very bright / washed out and the colours distorted. Any thoughts - is this a similar issue?

[tw2005]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

i was looking at a schematic and saw Lo = 215v, Hi = 220v .

so If vsus set to high in serv mode then probably should set to lo and adjust the PSu back. If it was already low, would also be nice to know if changing to Hi still increases voltage to 220.

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

I'll keep my eyes open. Shipping might be a bit on the expensive side.

[tom66]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

It is a nice TV, they are lucky. Wouldn't mind a 42" ST30 for a bedroom TV...

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Total expenditure on the TV was $170 with the kit and about 2 hours of time. I typically don't pay $150 for a 46" TV but I made an exception on this one since I like our 55" so much and also because I was confident it just needed the SC repair based on the 7 blink code. The in-laws are going to be quite surprised when I show up with this to replace their 2009 32" 720P Toshiba LCD.

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

I only adjusted the one pot. I was completely amazed that it was basically resolved at just 2-3V lower than what I started at. I've only tried adjusting Vs on some older LG sets and it seems to take a substantial amount more of a swing to make any difference on those. The entire adjustment on this one was about 1/2 turn of the pot and 210-220V was the range.

And tw2005, I also thought it was strange that it was factory set in that position and was at its highest setting. Makes me wonder how it was working correctly prior to the SC failure.

[tom66]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Before you button it up, make sure you didn't inadvertently adjust Vda if you fiddled with that other pot - it should be no higher than 60V. Ideally around 55-57V.

[tom66]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Nice fix! It's interesting that Vsus makes such a difference but I do remember seeing on avsforum regarding VT60 blobs and blue sparkles caused by high Vsus.

I did try high Vsus (225V) on a 2011 Samsung PDP to get rid of a grey band but didn't get sparkles... All it did was buzz a lot more so I set it up to 212V from 207V

[tw2005]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Interesting it needed adjustment if the seal was unbroken. what is Vsus set to in the service menu? Mine is set to low. Mind you I changed mine to high and barely any difference.

Anyway glad you got it sorted

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Thanks again for the advice / guidance.

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

You're a genius Tom as usual. I dropped the voltage down to just 216 and it cleared up. At 211 it started looking rough again so I settled at 213 and it is perfect. I'll take some pictures after I get my son to bed in a bit. I would have never thought a few volts could make that much difference. Not to mention they were factory set and the TV is only a few years old with less than 2 of actual use on it.

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

I think it's got to be VR251 near the bop of the board by the connector to the SS board bunt I want to be sure.

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Yeah. I knew that about Vsus but I'm used to the LGs with the Pot labeled.

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

I believe these should be adequate. I see two. Both on the right side of the board.

[tom66]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Panasonic call it Vsus (Voltage Sustain)

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

Let me get you a few pics real quick. I'm unsure which pot is Vs. There are at least two and I don't think they are labeled that way.

[tom66]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

220V is really quite high for a panel like this. (Panel response is quite nonlinear so going up by just 10V can have a huge effect.) And I have heard that high Vsus can cause blue and green sparkles. Try dropping Vsus to about 205V ~ 210V.

The best way to adjust Vsus is full white: Put a full white pattern up, and adjust it down until you see one of a few things:
- Dead/misfiring/intermittent pixels
- Pink banding on the screen (may flicker slightly)
- Unevenness to the white level, such as a light grey band

At that point, add 2V and call that the final voltage.

[aaronwt6]

Re: Panasonic TC-P46ST30 Fixed SC Board But Still Have a Display Issue

I took the board back out and checked all the ground connections. A few were sketchy but I don't think they were affecting anything. Cleaned those up and added solder to them. I checked Vs and it's 220V. This seems high to me but I haven't worked on a plasma this new and there's no label on the panel. Tom, if you get on here please let me know what if any other voltages I should check. I may get another board on the way for backup just in case. Assuming that the problem actually still lies in the SC board.