Panasonic sc tnpa5081 rebuild

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

can you have a look at the board and find the 30F125 IGBTs if it has them, tell me the location numbers too, get a meter and do resistance across all combos of 2 legs please and report back

[dolivas27]

Re: Panasonic sc tnpa5081 rebuild

Here are the reading on the buffer boards.

I will explain more about the Fluke 87V reading later that is why I asked you about the meter you used.

I will have to check the suffixes

Do you think I could have some bogus transistors from China?

[dolivas27]

Re: Panasonic sc tnpa5081 rebuild

can you have a look at the board and find the 30F125 IGBTs if it has them, tell me the location numbers too, get a meter and do resistance across all combos of 2 legs please and report back

Ok give me a second I was reworking the board right now to see what has blown again.

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

Here are the reading on the buffer boards.

I will explain more about the Fluke 87V reading later that is why I asked you about the meter you used.

I will have to check the suffixes

Do you think I could have some bogus transistors from China?

did you flip the leads around to see if they changed? I have a feeling I may have tried a different meter at work once and got weird readings, may have been an 87 or an Agilent.

Going on the 79 it does appear both sets are ok and I'd be using them on those figures.

[dolivas27]

Re: Panasonic sc tnpa5081 rebuild

did you flip the leads around to see if they changed? I have a feeling I may have tried a different meter at work once and got weird readings, may have been an 87 or an Agilent.

Going on the 79 it does appear both sets are ok and I'd be using them on those figures.

Lead flipping does not matter is the the voltage the meter uses for the test.

I was in contact with fluke about the discrepancy in readings and here is what I found out.

The Fluke 87V uses 8V for the resistance reading but remember that changes with the range.

The Fluke 79III / 75 use 3v and again changes with the range.

I could never get the 3Mohm reading you were talking about on the Q521 / Q551 it was driving me nuts so I decided to go out to my truck and get the Fluke 79III I was then able to get the correct readings.

So as you can see the way the resistance was measured makes a big difference.

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

Lead flipping does not matter is the the voltage the meter uses for the test.

I was in contact with fluke about the discrepancy in readings and here is what I found out.

The Fluke 87V uses 8V for the resistance reading but remember that changes with the range.

The Fluke 79III / 75 use 3v and again changes with the range.

I could never get the 3Mohm reading you were talking about on the Q521 / Q551 it was driving me nuts so I decided to go out to my truck and get the Fluke 79III I was then able to get the correct readings.

So as you can see the way the resistance was measured makes a big difference.

there you go, I just learnt something but I did find the results were completely different if the polarity is switched or at least was impossible to get accurate. I guess since these are all in cct it is just a guide but if those pnp/npn were bad I think resistance was obviously low or shorted. I have not had to relace many of those on this board.

[dolivas27]

Re: Panasonic sc tnpa5081 rebuild

Ok here is what I have for the 30F125 Transistors

They are Q621 & Q622

Not sure the order now as they are both out of the board.

1st 30F125

Pin 1 NEG
Pin 2 POS = OL
Pin 3 POS = OL

Pin 1 POS = OL
Pin 2 NEG
Pin 3 POS = .456M

Pin 1 POS = OL
Pin 2 POS = .470M
Pin 3 NEG

2nd 30F125

Pin 1 NEG
Pin 2 POS = OL
Pin 3 POS = OL

Pin 1 POS = OL
Pin 2 NEG
Pin 3 POS = 1.54M

Pin 1 POS = OL
Pin 2 POS = 14.9M
Pin 3 NEG

The both seem to test good in diode mode but the resistance looks off.

If I test in diode mode and put the NEG on PIN 3 and POS on Pin 1 to turn on I get 1.84V on both.

What do you have on yours?

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

Ok here is what I have for the 30F125 Transistors

They are Q621 & Q622

Not sure the order now as they are both out of the board.

1st 30F125

Pin 1 NEG
Pin 2 POS = OL
Pin 3 POS = OL

Pin 1 POS = OL
Pin 2 NEG
Pin 3 POS = .456M

Pin 1 POS = OL
Pin 2 POS = .470M
Pin 3 NEG

2nd 30F125

Pin 1 NEG
Pin 2 POS = OL
Pin 3 POS = OL

Pin 1 POS = OL
Pin 2 NEG
Pin 3 POS = 1.54M

Pin 1 POS = OL
Pin 2 POS = 14.9M
Pin 3 NEG

The both seem to test good in diode mode but the resistance looks off.

If I test in diode mode and put the NEG on PIN 3 and POS on Pin 1 to turn on I get 1.84V on both.

What do you have on yours?

got a ref for 1,2,& 3? Like g,c,e?

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

somewhere amongst all that I'd expect to see 47K ohms as a reading

[dolivas27]

Re: Panasonic sc tnpa5081 rebuild

got a ref for 1,2,& 3? Like g,c,e?

Yes that is correct and I am testing them out of Circuit.

If you can test a Q661 / RJP64F4A out of circuit I have a felling I have some bad parts just not sure which ones.

The RJP64F4A I received from utsouce and they look bad.

I order some more off of eBay from a guy in the states and they look much better?

[dolivas27]

Re: Panasonic sc tnpa5081 rebuild

somewhere amongst all that I'd expect to see 47K ohms as a reading

In circuit or out?

I have several here and none read that and the ones that I installed the last go around were pulled from a working TNPA5784 SC board

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

Yes that is correct and I am testing them out of Circuit.

If you can test a Q661 / RJP64F4A out of circuit I have a felling I have some bad parts just not sure which ones.

The RJP64F4A I received from utsouce look bad I order some more off of eBay from a guy in the states and they look much better?

can't help. Just relocated a whole house, took me 3 boxes just to find a 5081 to probe, spares , you got no chance of me finding that and i think I'm out of the rjp63F3a.

have not ordered for ages but I've had no issues but always a chance you could. also these need to be probed in a way to turn them on to see if they are ok but as for straight resistance I don't think you have much chance there, so long as they're not shorted.

I've tried comparing originals to supplied for resistance and they never match but they've all worked.

I was hopeful the 30F125 were still in and had a low resistance since you did not mention these as replaced which normally they go but not always dead short, maybe a few hundred ohms.

Going by an earlier post someone else failed on a 54" board. I'm out of ideas biut If I was in this situation I'd try a 50" board known to be good and if that blew then something is killing them.

[dolivas27]

Re: Panasonic sc tnpa5081 rebuild

Do you think if one of the transistors were bad it would power up with out the buffer connected?

I need to purchase a transistor tester.

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

In circuit or out?

I have several here and none read that and the ones that I installed the last go around were pulled from a working TNPA5784 SC board

in cct, everything I've quoted pretty sure is in cct

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

Do you think if one of the transistors were bad it would power up with out the buffer connected?

I need to purchase a transistor tester.

I don't think a tester will help. try googling IGBT test or FET test, with multimeter.

Diode mode.

I'm baffled how it works ok until the buffers are hooked up

[dolivas27]

Re: Panasonic sc tnpa5081 rebuild

I don't think a tester will help. try googling IGBT test or FET test, with multimeter.

Diode mode.

I'm baffled how it works ok until the buffers are hooked up

I know how to test the IGBT & FET with a DMM that is the thing they test fine.

They turn on and off ok and don't have any shorts.

The transistor tester would have caught the bad Q608 as it would have tested for the leakage. I got lucky catching it with the DMM

Ok I am going to rebuild this board one more time and see if I can get it to work again with out the buffers.

[dolivas27]

Re: Panasonic sc tnpa5081 rebuild

Do you know if I can power the TV on with the buffers connected to the SC but not connected to the screen?

Still wondering if the screen has a problem.

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

Do you know if I can power the TV on with the buffers connected to the SC but not connected to the screen?

Still wondering if the screen has a problem.

I've never tried it. i have on a LG 2010 FHD tried it because the panel was smashed and got away with it. But i disconnected everything from the panel , both sustains and the bottom drive boards (c boards)

I can't advise.

If the panel was bad then I'd expect the buffer to blow and the SC.

Long shot but is the ic724, 5v for the sd/su. check that is ok. pin 3 - Vfg 2.6k ohms. near that sc50 connector.

I'd expect it to be ok , only once I'have it bad but tyhe buffers were bad too with the 5V line shorted on the buffer boards

[dolivas27]

Re: Panasonic sc tnpa5081 rebuild

Nope not the problem just too tired I will attempt more this evening.

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

Check all the gate resistors are good on the IGBTs.

This could be a BS thought but the 30F125, DG402 & DG502 are all in banks in parallel. I'm wondering if any resistors are open that transistor would not be running and with the load maybe too much on what is? They can burn out but not always obvious visually.

think there's 10ohm, 5.6ohm 7.5ohm