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

[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

[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.

[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.

[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.

[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

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

[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.

[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?

[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

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

Around 210-215V for a high performance panel like this.

[richto]

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

Checked with a Fluke across the 2 heavy duty PSU connections to the SC board and it reads 204.8V. Turned the Vsus pot and it goes up to a maximum of about 209 volts with no change to the display. So I guess it's likely the SC board.

[tom66]

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

See if you can locate -Vad and Ve test points on SC and SS respectively. What do you measure on them?

[richto]

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

Have pulled it now and am returning it for another SC board. If I get the same symptoms I will start here again....Thanks.

[richto]

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

OK I fitted another new SC board - and behaviour is similar - the panel powers up with a complete but washed out picture. I also got a spare PSU board and swapped that out, but also no change.

A couple of times after about 5-10 seconds the panel has powered off with 8 blinks, but now it stays on. Vsus is 215V and Ve is 135V and Vad is 70V



Any suggestions how to proceed? Thanks.

The original SC board was definitely completely short circuit so i'm wondering if it's possible that the main AV board has been damaged via the linking ribbon cable?

[tom66]

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

I doubt the main board is bad.

It seems like it could be an SS or SC board fault but replacing the SC would generally indicate it is not SC. Can you supply photos of the SC and SS boards in your set?

[richto]

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

I doubt the main board is bad.

It seems like it could be an SS or SC board fault but replacing the SC would generally indicate it is not SC. Can you supply photos of the SC and SS boards in your set?

Petty sure the SC board is OK now, but it was originally short circuit. Can that impact the SS board? I have not touched SS so far. The picture is still just the same as the photo above.

nb - the 8 blinks above I think was caused by loose ribbon cable to SC20 - which is now fixed.

I think it must be the A board or SC / SS as the whole picture is effected, and any other board like SU, SD or C1 / C2 would only effect part of the screen I think.

Boards are the same design / part as the attached photos:

[richto]

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

I have now ordered a replacement SS board to try that.

I can't see how a failure of the SC could take the SS board out too, but it seems the most likely cause...

[tw2005]

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

have we tried flicking through all the test patterns in serv mode yet just in case this is A board? Is the Sc20 ribbon ok at both ends, not damaged or corroded? A removed sc20 ribbon will trigger 8 blinks and you said it was intermittent shutdown of 8 blink then just fixed itself?

I would not have expected sc would take out ss either.

[tom66]

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

They aren't chained on this model. It looks exactly like dodgy SC so can only think of one other possibility and that's bad signals to SC (or possibly SS but seems less likely)

Hard to tell without a 'scope on the outputs, can only do some basic volt checking.

I can't see bad SU/SD causing this.