Panasonic TH-42PZ77U 7 blinks

[Rockguy]

Hey guys. I read this thread https://www.badcaps.net/forum/showthread.php?t=24894 here about this problem. I've used the troubleshooting tree and it says replace the SC board. That thread also led me to it usually being a transistor. There are a lot of them there. One long row of like Q641 to Q654 and then opposite of that it looks like it goes every other one. Q 622 to Q627 part number 5N2307.

Do I have to unsolder one leg of every one of those and test it? Can somebody give me clear instructions?

[capkid]

Re: Panasonic TH-42PZ77U 7 blinks

This might be helpful. The 42PZ77U and the 42PZ700u use the same SC board: http://www.avsforum.com/forum/167-pl...l#post17876879

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

Thank you very much capkid. I guess that's what you have to do. Hopefully those legs come up fairly easily.

[tw2005]

Re: Panasonic TH-42PZ77U 7 blinks

if the transistor is shorted then should show short in cct. So are there any shorts showing on the banks of FETs at all?

[capkid]

Re: Panasonic TH-42PZ77U 7 blinks

Thank you very much capkid. I guess that's what you have to do. Hopefully those legs come up fairly easily.

I have a hot air station, but a heat gun on a low setting should work if you don't have a hot air station. Just CAREFULLY and gradually lift the legs enough so they're not touching the pads - no need to lift very far.

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

if the transistor is shorted then should show short in cct. So are there any shorts showing on the banks of FETs at all?

Would I be checking between the two legs for a short or the base/backside and each leg? Like this https://www.badcaps.net/forum/attach...6&d=1355870022

or this? https://www.badcaps.net/forum/attach...0&d=1355870368

[tw2005]

Re: Panasonic TH-42PZ77U 7 blinks

Would I be checking between the two legs for a short or the base/backside and each leg? Like this https://www.badcaps.net/forum/attach...6&d=1355870022

or this? https://www.badcaps.net/forum/attach...0&d=1355870368

I would check all 3 combinations. I assume your convinced it is transistors so rather than pulling up one by one, first you need to find there is a problem in a bank.

i would go base to both legs and then just the legs and look for low reading or short.

I guess what I'm asking is have you found a problem yet to justify lifting each transistor leg?

the photos show them doing pretty much that.

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

I would check all 3 combinations. I assume your convinced it is transistors so rather than pulling up one by one, first you need to find there is a problem in a bank.

i would go base to both legs and then just the legs and look for low reading or short.

I guess what I'm asking is have you found a problem yet to justify lifting each transistor leg?

the photos show them doing pretty much that.

I'm assuming transistors because it seems to be a common cause. I just went base to each leg. This is IN circuit. (no legs lifted) RL= right leg

I found Q641 RL=.045 LL=.386 Q642 same Q643 same Q644 RL=.045 LL=.319

Leg to leg shows .340 with the exception of Q644 which is .273

Opposite side Q622-Q626 all measured the same. RL=.392 LL=.952

Are these readings useful without any legs lifted?

Q645 RL=.045 LL.386 Q646 same

Q695 RL=.515 LL=1.014 Q696 RL=.515 LL=1.012

Q648 RL=.492 LL=.925 same readings for Q649 Q651 Q652 Q653 Q654

[tw2005]

Re: Panasonic TH-42PZ77U 7 blinks

I found Q641 RL=.045 LL=.386 Q642 same Q643 same Q644 RL=.045 LL=.319,Q645 RL=.045 LL.386 Q646 same

without knowing the board if these are together , this is the bank to start lifting the RL of each and retest that Transistor

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

I found Q641 RL=.045 LL=.386 Q642 same Q643 same Q644 RL=.045 LL=.319,Q645 RL=.045 LL.386 Q646 same

without knowing the board if these are together , this is the bank to start lifting the RL of each and retest that Transistor

This is the board the guy above was testing the exact same one.

https://www.badcaps.net/forum/attach...6&d=1355870022

[tw2005]

Re: Panasonic TH-42PZ77U 7 blinks

This is the board the guy above was testing the exact same one.

https://www.badcaps.net/forum/attachm...6&d=1355870022

something wrong with that link. Pooch has been on the booze again ERROR 404 not found

Is it a TNPA4250?

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

something wrong with that link. Pooch has been on the booze again ERROR 404 not found

Is it a TNPA4250?

Well........................... let's try again

https://www.badcaps.net/forum/attach...6&d=1355870022

[tw2005]

Re: Panasonic TH-42PZ77U 7 blinks

Well........................... let's try again

https://www.badcaps.net/forum/attach...6&d=1355870022

ok, yeah I had a quick look at the earlier links. I like the pooch better.

Anyway, start with that group of transistors

[tw2005]

Re: Panasonic TH-42PZ77U 7 blinks

out of curiosity start with Q644 since leg to leg was different

[tw2005]

Re: Panasonic TH-42PZ77U 7 blinks

Q622-626 any info on them?

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

Q622-626 any info on them?

622-626 were all the same RL= .392 LL= .952

[tw2005]

Re: Panasonic TH-42PZ77U 7 blinks

Hope I got this right

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

Hope I got this right

Yep, that's what I'm dealing with. I'll start with 644. I'll do that tomorrow though since it's 2 am here in the states. I appreciate your help tw.

[tw2005]

Re: Panasonic TH-42PZ77U 7 blinks

Yep, that's what I'm dealing with. I'll start with 644. I'll do that tomorrow though since it's 2 am here in the states. I appreciate your help tw.

yeah i may have been rude jumping in, but seeing how many FETs you were dealing with, I had this vision of you starting randomly on a bank lifting each when the bank was ok.

Down to 6 and if lucky q644 may be it. never touched these older sets.

enjoy, looks like a cheap fix coming up.

[Rockguy]

Re: Panasonic TH-42PZ77U 7 blinks

yeah i may have been rude jumping in, but seeing how many FETs you were dealing with, I had this vision of you starting randomly on a bank lifting each when the bank was ok.

Down to 6 and if lucky q644 may be it. never touched these older sets.

enjoy, looks like a cheap fix coming up.

You weren't rude at all. I'm grateful to get any help I can. I was kind of expecting a much lower number from a potential faulty part but, maybe lifting the leg will reveal more information.