Panasonic TC-P42ST50B - 7 blinks after some time

[tom66]

Hi all

My beloved Panasonic TC-P42ST50B that I've had for just over a year now has started giving me a 7 blink code after around five minutes of operation. The picture is absolutely perfect before the TV dies.

I'll take some pictures tomorrow when I have the back off, but wondering if anyone has heard of this before.

[tw2005]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

negative. Though the first step I guess you could monitor the voltages the SOS7 cct guards when it trips?

[tom66]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

I'll try monitoring SOS7 and sustain waveforms on the scope, if there's a time delay between one and the other it might clue me into what's going bad where. I'm thinking main board right now - probably BGA solder - ugh. But maybe I can borrow the reflow oven at work.

[tw2005]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

I'll try monitoring SOS7 and sustain waveforms on the scope, if there's a time delay between one and the other it might clue me into what's going bad where. I'm thinking main board right now - probably BGA solder - ugh. But maybe I can borrow the reflow oven at work.

built yourself a Tesla yet?

[tom66]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

built yourself a Tesla yet?

Soon, that or just buy one. Model 3 looks nice and I might even be able to afford it.

[tom66]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

Pictures inside. Very nice design.

Removed and inspected all sustain board screws, no sign of arcing. Power supply Vsus is nice 215V and steady before power is cut by A board.

Tested TP_SOS6 and TP_SOS7 and both are at 5V during fault, not sure what voltage level indicates a fault so may have to do a little digging.

[tom66]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

tw2005, curious if you have a schematic for the SN board of this model?

[tw2005]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

Pictures inside. Very nice design.

Removed and inspected all sustain board screws, no sign of arcing. Power supply Vsus is nice 215V and steady before power is cut by A board.

Tested TP_SOS6 and TP_SOS7 and both are at 5V during fault, not sure what voltage level indicates a fault so may have to do a little digging.

So before fault it's 0V? I'm pretty sure a high is shutdown. 5v is a high.

probably going to have fun tracking down a usable schematic

[tom66]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

So before fault it's 0V? I'm pretty sure a high is shutdown. 5v is a high.

probably going to have fun tracking down a usable schematic

Before fault it's 5V. Always 5V, then SOS7. I've got this: which tells me the 5V indicates a fault (slide 6).

Haven't yet got it to power up again, suspect it'll go high then SOS7 with trip out. Nothing obviously shorted on the board, and I know it generates sustain pulses which produces a good picture. Can't be sure if something like Vad is going askew and causing mild picture distortion before it goes bad, but it looks absolutely perfect before it dies (excellent PQ as expected from a Panasonic PDP!)

If it's similar to the '30 series, which I diagnosed (bedroom TV is a TC-P42U30B which had the shorted transistors with locked green LED) then it's a simple voltage comparator so it's looking at various rails to see if there's a fault.

But I've tested Vad, Vscn, Vfg5V and they are all good. Thinking it could be a faulty comparator or voltage reference, or something obscure. SN boards are scarce, so would like to fix it.

[tom66]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

Odd. SOS6 and SOS7 both go high after the sus cuts out...but... I was only able to get to this point by freeze-spraying the lower half of the SN board. So the SOS6/SOS7 may have nothing to do with the fault. They may be going high after some other fault latches out on the SN board.

Scope screenshots showing that SOS6 (1st pic) and SOS7 (2nd) are low before the sustain dies. And the sustain always cuts off on a frame boundary - just after last subfield of given frame. Really frickin weird if this is an A board issue. Maybe the A board samples an error signal (undocumented one, not SOS6 or 7) on each frame, instead of continuously.

[tw2005]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

This will have to do with the same SN

[tw2005]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

On sale , cheap enough not to break the bank even as a spare if it's not this board.

Ends 5.55 pm Lancashire time

http://www.ebay.co.uk/itm/YSUS-FOR-P...YAAOSww3tY39qQ

[tom66]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

Wrong board - my set uses the 1080p board and that's a 720p one

[tom66]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

Though found this board for about £16
http://www.ebay.co.uk/itm/TXNSN11WFD...kAAOSwuLZY5RUE

Should work in my set, so I might get it. Fairly sure it's the SN board at fault here. Kind of want to diagnose it. Running thought is something wrong with VFG5V or 15V as that area seems most affected by heat and freezer spray.

[tw2005]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

Right, that's a dagger in my heart, usually pretty good at getting it right.

So that makes the manual useless then. I saw XT50, normally 3D version should have had a closer look instead of rushing.

So the board is TNPA5523

Back to the drawing board then, glad you spotted it.

[tw2005]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

Next time I'll search TX-P42ST50B then, for the manual , LOL

[tom66]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

No worries, your help is appreciated! I bought the board, but I'm going to look at this one closely to see if I can figure out what went wrong. Then maybe I'll have a spare.

It does seem like the ST50 is much more reliable than the previous 30 series which was plagued by SN/SC board failures. Still on the lookout for a cheap 55-60" Panny PDP for the living room - of similar series to what I've got.

Thanks for the manual.

[tw2005]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

No worries, your help is appreciated! I bought the board, but I'm going to look at this one closely to see if I can figure out what went wrong. Then maybe I'll have a spare.

It does seem like the ST50 is much more reliable than the previous 30 series which was plagued by SN/SC board failures. Still on the lookout for a cheap 55-60" Panny PDP for the living room - of similar series to what I've got.

Thanks for the manual.

I picked a 65" V10 $20, My god only just fitted in the back of my wagon. Made good money on it but a part of me feels I should have kept it. Rare opportunity.

At least the 30 series is generally easy repair but the parts are obsolete

[tom66]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

OK, MAIN_STOP0 is the SOS7 signal and it's generated by IC725 (16725 on schematic S-30), heating this causes the board to stop working but during fault I can't see anything wrong-it seems to behave like a normal 5V regulator. The chip seems semi custom as it's a voltage regulator (15V to 5V) but also generates fault signals and has several unknown inputs going into it.

[tw2005]

Re: Panasonic TC-P42ST50B - 7 blinks after some time

OK, MAIN_STOP0 is the SOS7 signal and it's generated by IC725 (16725 on schematic S-30), heating this causes the board to stop working but during fault I can't see anything wrong-it seems to behave like a normal 5V regulator. The chip seems semi custom as it's a voltage regulator (15V to 5V) but also generates fault signals and has several unknown inputs going into it.

What marking is on it? If it fails with heat, could be it, does show it has a thermal pad so it must get warm in use. So if it's feeze sprayed, does it last longer?