Okay, I'm back. This is my last attempt at trying to fix my Panasonic. I've posted here before with questions trying to get my TC-P55ST50 fixed and got so frustrated that I shelved the project for a few months. Having a backup tv has really hindered progress on this thing.
To those who know more than I do and are gracious enough to give advice in this thread (ahem... TW2005), here is a brief summary of the problem.
I initially diagnosed the problem as an SS board problem with the 6 blink error code using the 2012 Panasonic troubleshooting guide I found online. (Side note: this guide states that it specifically applies to the TC-P50
ST50 and the TC-P50UT50 modles, but I assume that the blink codes for the 50" and 55" inch models are the same).
I replaced the SS only to get a new blink code of 8. Diagnosed the problem to be a bad SC and verified that the existing board had severe burns/brown patches all over the PCB. Several components also appeared to be shorted out. So I replaced the SC and SS yesterday.
Now I (presumably) have a working SC and a working SS board. I powered on the TV and got 8 blink again. Following the troubleshooting guide, I removed the connector from the SS to the A board and powered on again. TV turned on and remained on with black screen. Turned TV off and checked for continuity between pins 1 and 2 of connector SS52. This checked out ok so I then checked for continuity between pins 1 and 2 of SS54, SS55, and SS57 and these also looked ok.
At this point, the guide suggests replacing the SS2 board but I wasn't convinced. Having a fair amount of confidence that my new SS board is not the problem, I decided to focus on the SS2. Looking at the schematics from the Chassis guide, the SS2 board is very simple. Each of the 3 resistors were not shorted (meter showed 117kOhms each, but can't verify the actual resistance without removing the resistors). I also performed a diode check on each diode. I forgot to test diode D16362 but I doubt that there is a problem there as a visual check of the entire board showed no evidence of problems.
SO. Now I'm concerned that it may be a problem with the panel or the connection/connections from the SS/SS2 board to the panel sustain electrodes.
One last thing that I observed from the troubleshooting guide. For 8 blink errors, the guide states that the circuits monitored are the sustain drive circuit and the connection between the SS board and the panel. Conditions that could trigger this shutdown include: abnormality of the sustain drive circuit, open or loose connection between SS/SS2 boards and FPCs from the panel (SS52, SS54, SS55, SS57), Open or loose connection between connectors C10/C20 or C26/C36, or wrong diagnostic by the A board.
That's a lot of possibilities and I feel like I've eliminated most of them. I don't think the A board is a problem since the TV turns on fine when I disconnect the SS board. Also, the connections on the C boards appear fine.
Does anyone know if there is a way that I can verify that the problem is with the panel? Or have any other advice on circuits/boards to check out? Should I still try to replace the SS2 board? If it's the panel, I'll finally be able to send this TV into oblivion and get a new one but until I know for sure that it isn't a less serious and fixable problem, I can't let it go.