Panasonic Plasma Likes Naps

[seventy1]

Hello all, I'm new here and thought this would be a good place to get some advice on my Panasonic TC-P42GT25 3D plasma TV. It's a Nov 2010 model and about 3 months ago it started turning itself off after about 20 to 40 minutes of watching. It's been a good feature to minimize the kids' TV time, but I need to fix it. When this happens, it's unresponsive, won't turn back on, the remote and button on the side do nothing, no clicks, no flashing lights. If you leave it alone for about 15 minutes, you'll hear a click and voila, it comes back on!

It sounds like a thermal relay of some kind, but I'm not sure where to start. I'm no electronics technician, but I know my way around a multimeter and a soldering iron. I've got the TV on it's face on the dining room table and the back is off - what next? I did search the site before posting, but couldn't find anyone with a similar problem. Thanks for any advice!

Fritz

[tw2005]

Re: Panasonic Plasma Likes Naps

I'm going to say it's most likely the A board and maybe one of the BGA chips has broken solders that go open with heat. these boards do run very hot on that processer under the heatsink. i have the 50" and I'm amazed mine has not quit yet because of how hot that chip gets.

It'll probably take a pro to fix that board because specialised rework station would be need to get that chip off and maybe reball it and reflow it back to the board.
or find a good used one but moduslinkpts do repair them . not exactly a cheap board to fix.

next time it happens you could try freeze spraying the board and see if that brings it back straight away or heat it and see if it fails straight away but i can't think of any other board that would cause it .

[seventy1]

Re: Panasonic Plasma Likes Naps

Thanks, so there's no thermal fuse that would cut power then reset once it cools? Noob question, but where's the A-board? I can see if the chip (micro?) looks like it got hot.

[Moreno83]

Re: Panasonic Plasma Likes Naps

A board is the board on the righthand side with all the HDMI/Scart connectors. Let it run and see if one of those chips gets very hot or not. ( With the heatsink ).
Im also suspecting A board. You sure all capacitors look ok on the power supply?

[seventy1]

Re: Panasonic Plasma Likes Naps

I took a closer look at the power board, removed it to look at the back, no signs of over-temp or swelled or leaking caps. Then I put everything back together except the back cover to do the heat test and now it doesn't turn on at all. Are there some power test points that I can check? Thanks.

[R_J]

Re: Panasonic Plasma Likes Naps

This sounds like the power supply board may have a bad solder connection somewhere, I would check to make sure your plugs on the power supply are connected properly first (no bent pins) and if they are I would have a close look at the solder connections, mostly around the components that are connected to the heat sinks. maybe some clear pictures of the solder side of the p.s. board would help.
Did it give a blink code when it would shut down?

[seventy1]

Re: Panasonic Plasma Likes Naps

I never had any SOS codes, that I noticed at least. I just followed a trouble shooting flowchart that I found on Elektro Tanya: no relay click -> 5v standby voltage present -> unplug A1 on A-board, still no relay click -> replace the A-board. Argh! Not the answer I wanted. Now to see how much they are...

[freakaftr8]

Re: Panasonic Plasma Likes Naps

A board issues seem to have premature failure in newer panasonic plasmas. I think the heat sync is inadequate for the task at hand. Remember the slimmer they get the less cooling efficiency they have

[seventy1]

Re: Panasonic Plasma Likes Naps

Thanks to all for your input. I bought a used A-board off of the auction site for $135 and it appears to be back in business (just did a relay check so far).

I'm wondering if there are any mods that could extend the life of the under-cooled chips. I do have a 12v fan around somewhere that I scavenged off of a computer. I'm not sure how noisy it is, meaning audible and EMC. Is there a good place to tap into 12v on the power board? Bad idea?

[tw2005]

Re: Panasonic Plasma Likes Naps

Thanks to all for your input. I bought a used A-board off of the auction site for $135 and it appears to be back in business (just did a relay check so far).

I'm wondering if there are any mods that could extend the life of the under-cooled chips. I do have a 12v fan around somewhere that I scavenged off of a computer. I'm not sure how noisy it is, meaning audible and EMC. Is there a good place to tap into 12v on the power board? Bad idea?

I think if you can get a fan on it it would have to help. It's be intersting to get a temp reading on that sink but i have a 50V20 (2010) and it seems bloody hot for me to touch.

Did you keep the old A-board? Moduslinkpts do rebuilds. What board number did the old one have?

[seventy1]

Re: Panasonic Plasma Likes Naps

I did keep the old board, it's TNPH0893 1A nil suffix. I think it's unique to the 46". At this rate, it may be a good idea to keep a spare.

[tw2005]

Re: Panasonic Plasma Likes Naps

Interesting, I've got 2 TNPH0893 AB from a 50GT25 from new damaged in transit TVs. Was part of a complete boardset purchase in search of sc/sd/su boards.

I've experimented with eeprom swaps to convert boards to different sizes which works.


Comparing 42 manual these are the eeproms/flash chips and from the 50" manual we can see what's different.

If you have a eeprom read/writer and a clip you could copy and reflash without removal. Also new chips preloaded are available too from what I see and very cheap $7

42gt25
IC8502 TVRR831AAS TVRR831S
IC8501 TVRR830S
IC9304 TVRR833ACS TVRR833S
IC5801 TVRR904S
IC1101 TVRR944S

50gt25

IC8502 TVRR832AAS TVRR832S
IC8501 TVRR830S
IC9304 TVRR834ACS TVRR834S
IC5801 TVRR904S
IC1101 TVRR944S

To do a conversion only 2 need to be swapped, IC8502 & IC9304

IC9304 is the panel address data and I know a corrupted one of those can trigger 1 blink