Panasonic TH-42PZ77U SC board repair

[Sevenqi]

I got this tv with 7 blinks, sure it's the SC board problem, took the board out and mesured the FETs, look 6 of them were shorted, from Q641-646, the way I did was to use multimeter on diode position, the red pin on the tab D (I guess base of the FET), the black on the S and G.

Q641-646:
D-S: 14
D-G: 265

Q695-Q696:
D-S: 14: 5.4 M
D-G: 154 K

So I thought the 6 FET Q641-646 were shorted, but when I lifted the two legs of Q641 from the board, I measured the same way to the FET, I was surprised the value was different:
D-S: no value
D-G: no value
And I measure the same position on the board (S,G point on the board), I got the same value as 14 and 265.
Is the FET not good but the other parts like resitors or capacitors failured? How can I determine the FET is good?
Thanks

[tw2005]

Re: Panasonic TH-42PZ77U SC board repair

I think some other blokes have had some success with these. I have not read it all but sounds like it could be same SC board.
https://www.badcaps.net/forum/showth...light=sc+board

[tom66]

Re: Panasonic TH-42PZ77U SC board repair

Usually it's just one of those fets. Once you isolate the short you can power up the TV with 5/6 FETs connected and get a good picture -- don't run for more than 15 minutes. Then replace the bad FET.

[Sevenqi]

Re: Panasonic TH-42PZ77U SC board repair

I dissoldered all legs for the 6 FETs, exactly the same as TOM66 said, only one was shorted, I resoldered the 5 good FETs and the TV can turn on, the picture looks perfect!
Is there a problem to work with only 5/6 FETs ? I may take time to order one.

[johnboy1313]

Re: Panasonic TH-42PZ77U SC board repair

I can't say for sure what will happen running it that way, but it can't be good. The engineers that designed it put 6 FETs there for a reason and it still failed eventually. If it were me, I wouldn't run it that way.

[tom66]

Re: Panasonic TH-42PZ77U SC board repair

After the failure, a software update is recommended. While the software may be the primary cause it's not good engineering practice to run it with a missing fet.

[Sevenqi]

Re: Panasonic TH-42PZ77U SC board repair

Finally I found a FET from a Panasonic plasma board (TNPA3828, a SS board from a broken screen tv, it has 6 FETs), I took out one and replaced the bad one, after 3 hours watching, everything is perfect, the FETs are not hot. Thanks all for your comments.

[tom66]

Re: Panasonic TH-42PZ77U SC board repair

PLEASE do this before you consider it fixed.
http://www.panasonic.com/announce/updatemytv/

Otherwise it will fail again.

[Sevenqi]

Re: Panasonic TH-42PZ77U SC board repair

I like to do a test if there is a problem not to do the firmware upgrade after fix. 3 hours of watching, the tv shut itself off again with 7 blinks.
I ckecked the replaced FET, it looks not shorted, other FET also good,but still can't power on.
So finally I replaced that FET again, TV worked again. I did the firmwre upgrade this time as follow:
1. Format my SDcard (2GB) as FAT32
2. Download the firmware and instruction:
http://www.servicecare.net/blog/2008...pgrade-th.html
3. Save the SDDL.SEC file to the SD Card (One file only).
4.Turn on the tv, insert the SD card to the SD Card slot.
5. TV autodetect the firmware file, and ask to comfirm to download the upgrade file, select Yes.
6.TV was now upgrading the firmware, it took about 10 minutes to complete.
7. Follow instructions on the TV,unplug the power cable from wall, wait a few seconds, and plug again.
8.TV turned on and did the initilization, 3 minutes later, every was done.

I checked the TV version, it's now 0190-0020 (I didn't mark done the original version, hope this is the right version)
Status1:01001-20010
Status2:00000-00000

I'll watch the tv for a few hours to see if still problem tomorrow.

Thanks TOM66 for your advice.

[tom66]

Re: Panasonic TH-42PZ77U SC board repair

I notice Panasonic has pulled that site now; can you upload the files you used here for other people?

[Sevenqi]

Re: Panasonic TH-42PZ77U SC board repair

I notice Panasonic has pulled that site now; can you upload the files you used here for other people?

Sure, I uploaded the SDDL.SEC and instruction pdf.

[Sevenqi]

Re: Panasonic TH-42PZ77U SC board repair

Looks like badcap forum only allow some types of file to upload,so I changed the file extension SEC to pdf from SDDL.SEC to SDDL.pdf, please change the extension after download before using it.

[bjorkson]

Re: Panasonic TH-42PZ77U SC board repair

If you have a bad SC board, would it also take out the SU and SD board also? If you have to replaced the SC board, would it be a common practice to replaced the SU and SD also? I know in the Samsung plasma model, you have to replaced all the Y boards.

[tom66]

Re: Panasonic TH-42PZ77U SC board repair

These Panasonics usually do not have failures which damage the SU and SD, but on some newer sets, replacement of SU/SD is necessary after SC replacement.

[nstueve]

Re: Panasonic TH-42PZ77U SC board repair

Ok so I have the same 7 blink code and figure I'm in the right ball park reading this thread.

I was origionally thinking about replacing the SC board all together but now it seems easy enough to test out the FETs. Does anyone have a link on how to use a multi-meter to check the FETs? Also how do I find the correct parts online for replacement? Are there specific part numbers or a general electronic part number I can use to find one?

I've chipped a couple origional xbox's so soldering a on boards doesn't phase me. But I may ask some very novice questions that seem appartent since I'm more skilled inside a 2stroke engine than on electronic board repairs.

Cheers!

[tom66]

Re: Panasonic TH-42PZ77U SC board repair

You test the FETs by checking for shorts between all exposed pins; you can use the diode mode for this.

[nstueve]

Re: Panasonic TH-42PZ77U SC board repair

ok... Let me rephrase... I'm pretty much a complete newbie to diagnosing board problems so I probably need a little more description and direction since I don't know the basics. Pretend i'm 12 years old and your teaching me to do this... LOL! Working on the boards I feel comfortable with but still need more direction.

I can probably find the diode mode on my multi-meter but what am i testing between? From "pin to pin" or from "pin to board"? Do I need to detach all the pins/legs from the board if testing between the pin and board?

PS: thanks in advance for the help!

[tom66]

Re: Panasonic TH-42PZ77U SC board repair

No problem... we all start somewhere.

There are three pins, the two outer ones on one end, and the fat tab at the other end. There's a small exposed point on the bottom, which isn't connected to the board normally; ignore that for now.

Number the pins mentally from 1-3. There's no particular order, but be consistent between each device.

Set your meter to the diode range, and test the following combinations

red probe - black probe
1 - 2
1 - 3
2 - 1
2 - 3
3 - 1
3 - 2

Then we can see if there are any bad devices.

[nstueve]

Re: Panasonic TH-42PZ77U SC board repair

Thanks so much for the help. That is a set of directions I can follow! I have a friend at work that has soldered lots of electronics and said he'd help.

And just to be 100% crystal clear, do I need to desoldier the two legs of the FET every time I test in the sequence with my meter (pic 2 above)? Or do I only need to desolder for replacement of the bad FET? From what I think I understand, I'm trying to find the bad electrical pathway inside a FET and then replacing..?


Lastly, if we find the bad FET how do I locate one online (the part number on the bad unit?)?

Thanks!!!

[tom66]

Re: Panasonic TH-42PZ77U SC board repair

Assuming 5N2307
http://www.ebay.com/sch/i.html?_trks...at=0&_from=R40