Panasonic TCP42S30: Repeated SN Board Failures

[Nonsuch]

We really like the picture quality of our Panasonic plasma, but a recurring problem with the SN board is making us question keeping the tv. First it was a solid red light SOS. We sent the SN board to a repair shop, and it worked fine for the next 9 months. Then it was a six blink SOS. The 2011 Panasonic Troubleshooting Flowchart said it was the SN board again, so we sent the board to a different shop. It lasted 4 days this time, and then gave the 6 blink SOS again. Hopefully the repair shop will honor their 90 day warranty.

Is this repeated SN board failure likely to keep happening? I don't know which specific parts have been replaced on the SN board, but I can see some flux stains around several transistors and diodes. There is now a youtube video on diagnosing and repairing SN board failures. I have a cheap multimeter and heat gun, so I might be able to do future repairs myself. But the prospect of wondering if the tv is going to work each time we turn it on and taking the time to make very temporary repairs has us questioning keeping the tv. I have a very limited knowledge of electronic circuitry and testing. Does anyone have any advice on how to proceed? Replies are appreciated.

Thanks to the Badcaps members who posted links to the Panasonic 2011 Technical Guide and Flowcharts and posting info on techniques for removing and installing the ribbon cables between the panel and SN board. We were about to give up.

[nicholas1110]

Re: Panasonic TCP42S30: Repeated SN Board Failures

Hello,

These boards fail mainly due to the screws becoming loose and causes an arc between the ground pad around the screw hole and the chassis of the tv. You can either use the updated screws with the locking washer(shopjimmy sells them) or some loctite works as well. You will also need to reflow the solder on the ground pads that have been damaged from the arc, and clean up the screw holes on the chassis as there will be black burn marks. At our shop we have not had one of these 2011 models come after making sure they have locking washer screws. Hope this helps.

[Nonsuch]

Re: Panasonic TCP42S30: Repeated SN Board Failures

I replaced the screws that hold the board to the chassis with ones with washers supplied by the shop that did the first repair. I will carefully inspect the ground pads for evidence of arcing when we disassemble the tv this week. If you have not seen repeated failures of the SN board at your shop, that tells me something else besides defective parts is causing the problem with our board. Thanks for the reply.

[tom66]

Re: Panasonic TCP42S30: Repeated SN Board Failures

I repaired a TC-P42U30B which is roughly identical to your set minus the smart Viera features.

The build quality on these low end, 42" FHD pannys is pretty poor to be honest. The surface mounted IGBTs seem to fail frequently. Picture quality when set up right though is really good, especially good for a low end set, it's just a shame they let the rest of the side down with the bad build quality.

6 blinks suggests an ERC circuit failure, I had that after a cold joint on some SMD driver chip for the ERC IGBT. Set would have a very brief screen glow then go out... only a 1/2 second flash.

If you do not get this screen glow it suggests other parts are bad, possibly a SUS UP/DN IGBT (though this usually causes red locked out LED.)

[Nonsuch]

Re: Panasonic TCP42S30: Repeated SN Board Failures

Thanks, Tom. We'll see how this repair goes. If it fails again then maybe we'll try a different SN board. Nicholas said he never sees repeat failures on SN boards, so perhaps the failures are caused by a problem with our particular board.

[nicholas1110]

Re: Panasonic TCP42S30: Repeated SN Board Failures

Hello,

These sn boards are build cheaply. There are no heat syncs and no fans in the tv. When we repair one of these s30 boards, there is 4 smd resistors that we replace as well. Probably half of the boards we have done the resistors were open. No matter if they are open or not we replace them. Also in a few of them ic502 and q531 were needed as well. To help keep these s30 TVs to lasts longer, make sure there is proper air flow around the tv (don't mount it on the wall as close as possible) and never run the tv in vivid picture mode. The brighter the picture the hotter the sn board will run. I strongly feel if you keep these TVs cooler the longer they will run.

[Alastair E]

Re: Panasonic TCP42S30: Repeated SN Board Failures

The SN boards run extremely hot. Hot enough in fact to scorch the board around the IGBT's...

I did one a little while back and added a small fan to the middle of the SN board powered by the 15V rail.

It kept the board very cool, it only getting tepid in temp--instead of burning hot!

Its just CRAP Design, cost-cut to the extreme. Personally I think the pictures it produces are pretty crap as well! Too much flicker and too much floating blacks....

[Nonsuch]

Re: Panasonic TCP42S30: Repeated SN Board Failures

Not certain, but think it's set to vivid mode. Will check when we get it running again. It took a lot of adjustment to get the picture quality we liked. Then we upgraded our cable package and the cable guy botched up the picture before he left. Might try the cooling fan idea. Thanks.

[tom66]

Re: Panasonic TCP42S30: Repeated SN Board Failures

It's funny Al because once I adjusted the set, turning off CATS mode, I liked the picture. I never had floating black or flickering. Maybe a difference in firmware? Not quite as bright as a PZ70/80 but made up in every other way. Only pulled 180W from the wall too.

[Nonsuch]

Re: Panasonic TCP42S30: Repeated SN Board Failures

I considered that the SN board was running too hot and caused the last failure. One IGBT had a scorch mark around it, and the IGBT's that were replaced were near the top of the board where temperatures might be highest. Like Alastair mentioned, I can easily add some fans to pull hot air away from the SN board. I found 80 mm fans with USB power that should easily mount on the ventilation holes over the SN board on the tv rear cover (Coolerguys Dual 80mm USB Cooling Fans, $16). High temps may not be the problem, but if it is, it's an easy and inexpensive fix. Perhaps Panasonic tried to save a little money by omitting fans from this model?

[freakaftr8]

Re: Panasonic TCP42S30: Repeated SN Board Failures

Add the tc-p55ut50 and 50 series to the list. Bad cooling and minimal heat syncing.