Panasonic Plasma weird colors, screen pulsing

[keats11]

I picked up this TV online, without knowing that it had problems. When I brought it home, it showed weird colors on poweron but it cleared up after say 5 minutes of running. I removed the SC (Ysus) board to inspect it up close, found nothing shorted or tampered with, so I put it back in, except I didn't put all the grounding screws. Upon power on, something blew on the SC board and gave me 6 blinks. Pulled it again, and upon examining up close, saw Q621, & Q661 shorted. Also IC773 (I think is an inverter) was shorted vdd/gnd. Ordered these parts from China and replaced them today, now the TV does fire up, the screen looks good for 2 seconds, when it starts pulsing with weird colors messed up at the same time. After a minute, the pulsing stops, but the weird color problem stays. I didn't keep it on longer than 2-3 minutes at a time, worried something might blow. At this point, looks like the repair is stable (it survived several power on attempts), but seems to be back to square one where I started. I have attached two pictures, first one immediately after power on (looks good) and the second after 2-3 seconds (colors messed up). Any have have any ideas what is going on here?

[tom66]

Re: Panasonic Plasma weird colors, screen pulsing

What is the model number of the TV?

[keats11]

Re: Panasonic Plasma weird colors, screen pulsing

Its a TC-P50C2. I noticed today that if I set the picture settings in the menu to be "Standard", it does the flickering and display poor color. However, if I set it to say "Cinema" or "Vivid", it looks good (no color distortions). Also, although unrelated, there is a faint greenish line across the screen right at the middle, several pixels wide. It is probably related to aging buffers, but I thought I'll mention it here. So really confused.

[keats11]

Re: Panasonic Plasma weird colors, screen pulsing

I thought this could be a Vsus problem. The measures Vsus was 189 volts when it first fired up and drops to 174 once the screen comes on. There were no labels on the screen stating what the Vsus value should be, but the service manual seems to suggest a value of 198. I increased the voltage slightly and now the picture looks good in all different picture modes. My guess is that the guy who sold it to me played with the Vsus settings trying to get what was a SC board issue to work, and lowered it to compensate for some weak component on the SC board.

[keats11]

Re: Panasonic Plasma weird colors, screen pulsing

I take that back, the problem still exists if I set the picture settings to "standard". It works fine in "Vivid", "Cinema" etc. No idea what is causing this. At this point I dont think it is a VSUS or SC board issue, as the behavior of the SC board should not change based on the software picture settings. May be worth trying an software update? But this thing needs a SD card.. sucks..

[keats11]

Re: Panasonic Plasma weird colors, screen pulsing

Not sure anyone is paying attention here, but looking in the service menu, I see that the last 3 blink codes had been 8,6,6 and the first 2 had been 6 and 6. So I wonder if the blink code of 8 has anything to do with what is happening with the colors. According to Panasonic this is related to SS FPC detect. Does anyone know what that stands for?

[freakaftr8]

Re: Panasonic Plasma weird colors, screen pulsing

Drive signals get generated from the control board and that being I believe on your model the control board is integrated with the main board. What kind of vsus are you getting in vivid or custom modes?

[freakaftr8]

Re: Panasonic Plasma weird colors, screen pulsing

Have you tried tweaking the vsus slightly higher in standard mode to see if problem starts to dissappear?

[ReeceyBurger123]

Re: Panasonic Plasma weird colors, screen pulsing

Also check that the Lvds cable is properly seated its a red cable I think on this model.

[tw2005]

Re: Panasonic Plasma weird colors, screen pulsing

Also check that the Lvds cable is properly seated its a red cable I think on this model.

Pssst (It don't have one) 2010 model, single A board, flat ribbons

[keats11]

Re: Panasonic Plasma weird colors, screen pulsing

The Vsus voltage as measured by one of my multi-meters jumps around in the 140-180 range. It varies a little bit ( I think it increases), in the custom mode). Out of curiosity I attached an older multimeter in parallel, and the Vsus read more stably on that one, at about 188 volts. Not sure if the older multimeter does a better average than this other one. Did I mention that in the service mode, if I try the "Vsus test", which is supposed to produce a white screen, instead produces a flickering screen, almost as though It cannot handle a fully white screen. Ill try to posy a video of it when I get home. This is a really strange problem to say the least.

[ReeceyBurger123]

Re: Panasonic Plasma weird colors, screen pulsing

Pssst (It don't have one) 2010 model, single A board, flat ribbons

Doh lol

[freakaftr8]

Re: Panasonic Plasma weird colors, screen pulsing

How many hours are on the panel?

I wonder if what the voltage is from the scan drive to the buffers on a full white screen? Have you tried applying heat to the SC board while you have a full white screen and its flickering?

[keats11]

Re: Panasonic Plasma weird colors, screen pulsing

I made a video of the TV problem, can be seen here:
https://youtu.be/3SSyoCW5XTw

[keats11]

Re: Panasonic Plasma weird colors, screen pulsing

A little more update on this problem. As luck would have it, someone in my town was selling this very same tv in fully working condition, so I bought it for the purpose of swapping boards to isolate this problem. To my surprise the A board (main board) seems to be the problem. Installing the problem A board in the known good tv recreated the color distortion and Vsus test issues. No idea what could be causing this, at least I won't be engaged in a wild goose chase here.