Panasonic TH-42PZ800

[nervx]

Last week my plasma started to dither and flicker then shut off, 7 led blinks.
I tracked down the service manual and followed the steps.
-disconnected the SU/SD board, 7 blinks
-disconnected the SC board, solid red

I thought i had it figured out but i wanted to make sure and needed to get the part number. So a day later i opened it back up, followed the same testing and now i get 8 blinks. wut?
It's been 8 blinks since.

This would indicate the SS board or panel is bad according to the manual but here's something odd. If i unplug the tv for a while it will work again like normal for a random amount of time. At first i left it unplugged for an hour or so and it worked for maybe 30-40 minutes, then i left it unplugged for a day and it worked for 4 days. Today it shut off again (8 blinks) so which brings us to this thread.

I made a video showing the problem, you can see it flicker a bit at the bottom before it craps out. Where it flickers and how much seems random.

https://www.youtube.com/watch?v=_i4_IYRCfvc

Im not sure whats causing the problem so im hoping maybe someone else will. Any help would be greatly appreciated.

[tom66]

Re: Panasonic TH-42PZ800

Hmm, I'd check the Vsus on the power board, it can cause symptoms like that when it goes bad.

[Alastair E]

Re: Panasonic TH-42PZ800

I would check the SS board for dry-joints, --Just before it shuts down it appears the picture goes very dark for a split second then shuts down completely.

[nervx]

Re: Panasonic TH-42PZ800

I couldn't see any dry joints and couldn't see any vsus test spots on the power board itself. There is a tpvsus point on both the ss and sc board near where the 4 pin power connects, are those the correct test points? the only voltage listed on the panel is for vsus which is 202v.

the sc board reads: 199-200
the ss board reads: 201-202

Are those readings within the margin of error for a plasma?


Another finding: After it starts to 8 blink If I try to turn it back on right away it shuts off within a few seconds. If I disconnect connector ss33 as the guide states the tv does stay on.
The next step in the guide is to check the voltage on the d280 anode and it reads 0.08v when it should be 2.7v. This would mean the ss board is bad but if that's the case any idea why the tv started with 7 blinks?

[nervx]

Re: Panasonic TH-42PZ800

sc board should be 199-201

and I forgot to mention those voltages remain steady even when the screen is flickering right before it shuts down.

[tom66]

Re: Panasonic TH-42PZ800

Ok, now try checking Ve (on SS board) and -Vad and Vscn on SC board.
I have a nearly working TH-42PZ8BA here that I should be able to compare voltages against, if you need help (Bad A board but panel lights up and shows test pattern)

[nervx]

Re: Panasonic TH-42PZ800

tv with nothing being displayed.

SSboard
TPVe 157.9

SCboard
TPVad -140.4
TPVscn 7.93

[tom66]

Re: Panasonic TH-42PZ800

Both of those match my set.
Does Vsus or any other voltage begin to vary or drop as the picture begins flickering?

[nervx]

Re: Panasonic TH-42PZ800

Both of those match my set.
Does Vsus or any other voltage begin to vary or drop as the picture begins flickering?

no as mentioned vsus stays stable even when the picture is flickering like crazy. the only voltage that is low is the anode the service guide says to check on the ss board. its 0.08ish when it should be 2.7v. I measured it a number of times because it was so low. im not sure what the anode is measuring and I've checked the board carefully front to back but couldn't find anything wrong with it.

the only other thing I can think of is the d board but if the manual is correct it should be fine. since the tv works for a while after being unplugged for a few hours maybe heat has something to do with it. Replacing the ss board should be a safe bet at this point right?

[tw2005]

Re: Panasonic TH-42PZ800

no as mentioned vsus stays stable even when the picture is flickering like crazy. the only voltage that is low is the anode the service guide says to check on the ss board. its 0.08ish when it should be 2.7v. I measured it a number of times because it was so low. im not sure what the anode is measuring and I've checked the board carefully front to back but couldn't find anything wrong with it.

the only other thing I can think of is the d board but if the manual is correct it should be fine. since the tv works for a while after being unplugged for a few hours maybe heat has something to do with it. Replacing the ss board should be a safe bet at this point right?

When I looked at this , I saw high = SOS trigger, low is Normal

Under normal condition, D16282 conducts keeping Q16280 on. When
Q16280 is on, a low is provided to the anode of D16280 (D280).
If a short circuit is detected, Q16280 turns off and a high is provided to the
anode of D16280 (D280). This high is provided to pin 66 of the CPU in the
D board. When this happens, the TV shuts down and the power LED blinks
8 times.

You could temporarily isolate that diode and confirm the other part of SOS8 that monitors the output from the Q042,051 is causing the trigger. Does sound heat related so fractured joints or dry joints would be on my list, not always obvious, reflowing may get lucky?