The seller reported that the device won't start and blink 10 times. I pulled the service manual from elekrotanya.com and looked it up:
Wow. That's a long list of possible failures! As the price was ok I dared to go for it.
The service manual is a delight. The best I have ever seen. Schematics and layout of all(!) boards are in zoom-able vector format. There are block diagrams, which give you a good overview of the main components. Very thorough diagnostic and miscellaneous service information. This is what you get from a manufacturer who does everything himself and not buy from others.
Back cover removed and the usual excellent Panasonic build quality shows:
The difference between this 2010 model and the 2011 Neo Plasma TX-P42ST30 I repaired earlier this year is significant. Everything is much bigger and clunkier. Even though the circuitry is probably very similar, the large semiconductors in this one are still through-hole as opposed to SMD in the later model. Cooling is passive with large heatsinks without fans.
So, my first check on a Plasma always goes to the SC board. But what's this?! A diode and transistor are missing! The cheeky seller did not tell me about that. Bastard. That was the reason for the 10 blinks in the first place, but what's the rest of the story? So I began measuring. I found those parts to be dead:
missing: D482, Q452
short: Q421, Q422, Q403, Q402, Q521
burnt, open or off-value: R421, R551, R522, R521
From that point on I did not bother investigating any deeper. After plowing through this thread in the Badcaps forum I realized that the SC board was severely damaged and a complete overhaul was the only option besides getting a used, working one. The board has the tendency to blow up again if not all of the dead parts are properly replaced.
The repair kit from GTV Watford in the UK, which is a very good source, costs 84€ including shipping and is a hell lot of work (27 parts). Luckily, I also found a board for 68€ from an Italian on eBay.
That board had one rub though. It was the AY type for the 50 inch 3D panel. I needed an AH type. What's the difference? See for yourself:
The only differences I found were the coils and the capacitors around them. The green and blue big drops and one electrolytic. A guy in a forum explained that this circuit is tuned in resonance with the individual panels to suppress electromagnetic emissions.
The board from Italy measured flawlessly. To be safe that none of the Y-buffers had killed the SC board, I removed all the panel connectors and measured the buffer outputs for shorts as well as the pins on the connectors to the SC board. No findings.
Now, to morph the AY into the AH type I swapped out the differing parts.
Board put back in and the TV worked. Almost. Because I removed the panel connectors, I had to go through the incredibly tedious routine of refitting them, which never works at the first attempt. The latches of the sockets on the buffer boards have the tendency to push the flat cables out of their position. Horizontal black lines and blocks all over the screen was the result. After 20min of trial and error everything was sitting were it should and Frau Johansson looking gorgeous as ever.
This older generation of Plasmas does not have the stunning image quality of the 2011+ Neo Plasmas. It is interesting that the image looks "analog", as if a CRT TV was pimped for HD. Nowhere as overly crispy digital and bright as modern LED LCDs are. It is pleasantly smooth and totally natural. This model also has an expert mode with countless image adjustments.
So, this adventure once again confirmed my impression: Panasonics are the best. Period.
I have a Panasonic tc p42st30 plas-42 just had the sn board replaced and it burned out about 1 hour later. what would do that?
ReplyDeleteIt can be just bad luck or perhaps the board was refurbished with bad parts. That's my best guess.
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