Panasonic sc tnpa5081 rebuild

[bregva]

Re: Panasonic sc tnpa5081 rebuild

Another tip, until you get it going properly, I would not risk the buffers just in case there's a chance the SC damages them when it blows. I would re-check them for piece of mind.

None of my buffer boards were hooked up until I proved my repaired boards good which is straight forward.

SC50 is a factory test connector which allows the SC to powerup fully without a SOS trigger due to disconnected buffers.

Simply short those 2 pins together which ever way you can(small alligator clip should do it) and if the Tv completes its startup and no blinks, it's good to go.

OK, finally was able to get to this project again
I'll try to answer your questions
Yes, I decided to fix the board versus buying replacement after finding this forum, and don't regret doing it even though replacement parts will eventually cost me almost same after all, but that itch was hard to resist, what can be better than learning something in the field you work and you love what you do
Anyway, I have already 4 SC boards in my posession since I started
1 AF version from the TV (not working, project) TCP50G20
1 AF version from friends shop (not working, became donor)
1 AH version from his shop (not working, has less damage then other two) goes on 42" TV according to Shopjimmy
1 AL version (working, but from TCP54VT25 model)

So here is the list of parts I've replaced:
D451 (short)

IC521, M81737FP (short between pins 7 and 8)
IC501, M81737FP (put it back in, looked ok)

Q452, 34G128 , shorted
D482, RFN25, shorted

Q421, Q422 , DG402RP, both shorted

Q402, Q403 DG502LW, both shorted

IC773, Schmitt inverter(HA), shorted

Q701 (7EW), shorted
Q702 (C3W), shorted

Q661 RJP63F3A, shorted

5V regulator IC724 checks good on all boards
All C541's check good on all boards

After parts listed above were replaced, Q661 blew again and I found that Q621, 30F125 shorted and Q622, 30F125 was open
I can't imagine I missed those 2 first time, but can't be 100% positive
If I did miss them that should explain why Q661 blew again, right?

Now I have several parts in transit, so untill I get them from China, I can't do much, but wonder what should I do after I get the parts:

1. Replace Q661 again on the board along with 30F125's and taking your advise plug it in with buffers disconnected
2. Do the same plus replace that M81737FP I did not replace first time
2. Rebuild another AF board, which has 30F125's intact
3. Restore AL version to working condition and take a risk and try it on the TV, even though it is from larger TV
4. Repair AH version (it has q701,702 and IC773 intact) and plug it in, even though it is from 42"
5. All of above, without plugging 42 and 54 versions, since I will probably have enough parts

David

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

looks as messy as the 1 I'm fighting.


D451 (short) I swear mine was good when i started , shorted now on this board,thanks

IC521, M81737FP (short between pins 7 and 8) 2 boards vcc/gnd virtual short, did not check 7/8. current board have replaced again as suspect out of cct vcc/gnd was 15kohm should be mohms,7/8 open should be Mohms, was new chip but collateral damage

IC501, M81737FP (put it back in, looked ok)all 3 boards this was ok

Q452, 34G128 , shorted i think you mean 45G128, no problems on all boards but now is on this one after several powerup attempts
D482, RFN25, shorted as above, failed together,
Suggest you also check 100ohm resistors R521,522 1 had burnt open.

Q521,551 1 was definitely bad, replaced both they're a PNP/NPN paired(sanyo CPH5524).R552 burnt high resistance, failed along with above

Q421, Q422 , DG402RP, both shorted both shorted

Q402, Q403 DG502LW, both shorted both shorted

IC773, Schmitt inverter(HA), shorted shorted

Q701 (7EW), shorted shorted

Q702 (C3W), shorted shorted

Is 3.9K R707 ok, I blew mine(fail #1)

Q661 RJP63F3A, shortedshorted

5V regulator IC724 checks good on all boards 1 fail

All C541's check good on all boardswas 5v resistance good = 5.6kohms across C561 (may show 8k for a blink) Also check/compare NAND IC691 to your good board, mine was bad and ties in with those C541 buffers.

Check R680, should measure 4.7K, if it shows 2.4k head for Q818, mine was bad.

After parts listed above were replaced, Q661 blew again and I found that Q621, 30F125 shorted and Q622, 30F125 was open

chances are you may have missed the shorted one, can read open as the FET needs to be switched on, i think blk to pin 3, red to 1 then red on 2 and should read. short 3 pins with finger and go blk 3, red 2 and should read nothing. 2 boards had 1 shorted , 1 good

Is opto PC561 compare ok to your good board, 1 board had failed.

across D790 does resistance = 1230ohms ? (15V in)


A less damaged board might be an idea, but I know I'm taking my time with this one now but you saved me with that diode. I'm betting that's all I missed again.

Items replaced(or to be replaced before next power attempt)

Q818, Q452, D482, R552, Q501,521, IC521, D451,Q661

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

I just realised your 54" board is a 3D model. The cct for the SC and buffers is different. I think you'll find the HA inverter is relocated to a different part of the board.

You should be able to hook up any of those boards for final function test provided you do not connect the buffers and SC50 jumper.

I made a mistake and purchased a 3D board but after looking at the schematic, pinouts for SC20 were the same so I hooked it up, no buffers, jumper sc 50 and it passed.

Doing this will not save the SC board, so if it's bad, then Pop! What I hate with this is when the SOS takes longer to come up and you think you've got it and then, pop right when the screen would energise. Damn I hate that.

Keep the info coming, I've been looking for someone to have a go as 2 heads, 2 different approaches should yield a result. As you've seen you helped me with a diode I have not bothered to rechecked, I'll have to go over the board again just in case.

I like to think although it has cost me more than expected, it's investment in knowledge. What I can see happening is these boards no longer available unless we stop board swapping and throwing them out. It's nice feeling getting some interest in this and I want to see other people have a win.

One board cost me $20 to fix the other $7, this one don't ask but my initiial investment was about $90 in parts for 4 boards. Turned out some were not needed so probably $40 more than i needed although I'm using them now.

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

Also check 10ohm R551 that blew too, part of ic16521 cct

[bregva]

Re: Panasonic sc tnpa5081 rebuild

Also check 10ohm R551 that blew too, part of ic16521 cct

Thanks, I'll check that tomorrow

Here are results of today's testing

First of all there are no resistors in location R552 on all boards I have
I wanted to show picture, but can't figure out how to attach it to the text

R521, 522 checked 100ohm on all
R707 3.9K are good on all
IC691 compared well to good board on all
R680 measured 4.7k on all

I can't find opto PC561, can you help?

I found interesting measurements on D790. In diode measure mode on my Fluke 77, it measured .850- .900 on 3 boards, except on AH i got .475. Huge difference. In resistance mode 3 measured 1366, 1414, 1420 ohms (pretty compartible), on AH version 1127ohms. I think it must not be critical part in the design, IMHO
Q818 measured good on 3 boards, and again on AH 2 pins measured open, and this one is the board with less damage than both AF's!!!

BTW, IC773 on AL is in the same exact location as on others

So I'm leaning towards idea that my board blew again because I missed q621 and q622, I'm gonna test them tomorrow, was short on time
Yours, however needed diode D451. Hopefully that's the culprit

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

Thanks, I'll check that tomorrow



First of all there are no resistors in location R552 on all boards . That's because it's R452 below for Q452, my bad eyes again!. have you got the manuals for the Tvs. Searching the PDF is the quickest way of finding some of these.

I wanted to show picture, but can't figure out how to attach it to the textGo advanced, manage attachments, JPEG is best watch the file size

R521, 522 checked 100ohm on all
R707 3.9K are good on all
IC691 compared well to good board on all
R680 measured 4.7k on all

I can't find opto PC561, can you help?Right next to SC20 connector PC461, my bad

I found interesting measurements on D790. In diode measure mode on my Fluke 77, it measured .850- .900 on 3 boards, except on AH i got .475. Huge difference. In resistance mode 3 measured 1366, 1414, 1420 ohms (pretty compartible), on AH version 1127ohms. Treat the AH as suspect bad, that's what I had on this board. It's now back to the others with IC521 replaced again + Q521,Q551 replaced.Q818 measured good on 3 boards, and again on AH 2 pins measured open, and this one is the board with less damage than both AF's!!!Sounds sus, with mine it did not show short but conducted more like a diode on all pins. I've been Resistance checking and diode mode checking now on some of these doubtful parts to give me a clue

BTW, IC773 on AL is in the same exact location as on othersYou're right, memory not good, just checked and all around IC792 is different, IC564 populated on 3D model

So I'm leaning towards idea that my board blew again because I missed q621 and q622, I'm gonna test them tomorrow, was short on time
Yours, however needed diode D451. Hopefully that's the culprit

Don't forget R552, Q521,551. I think these 2 transistors are a big part of why I've had to redo IC521 and the resistance anomaly. C561 resistance 5.6K ?? 5V in

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

I've hit the skids. I simply can't get this going. Replaced everything I could find, plus I went over it and sure enough one of my 30F125 had blown, replaced that along with the diode and resistor etc etc.

Powerup, 6 blinks no pop and at that stage i don't believe anything had blown. Q661 was ok and the 45G128. So I thought i may not have the jumper right, reseated it and second go loud pop. Q661 dead, Q452, d452 gone, gate resistor gone etc etc and these were never a problem.

I should have stopped as you'd get 7 blinks with the jumper not right, not 6. Just could not accept i had failed again but no, I had to tempt fate again!

Whatever it is I can't find it and I think short of replacing every surface chip and transitor i don't think I can get it . Simply not worth persisting I don't think.

So I'm thinking you did not miss that transistor after all and you may have the same ongoing problems as me. The 400V diode that's blown I can't get and took it off a good SS.

I can't risk it any more parts. Maybe you should bail out of yours and try the other AF?

Anyway I can't help much more except if you want readings off a good board but I checked so many resistances etc, all matched up so I'm missing some part of the cct. There's a couple of tiny comparators I desoldered and put back but if it's those i'll never know.

Stumped.

[tom66]

Re: Panasonic sc tnpa5081 rebuild

I'm wondering if it's practical to insert a lamp in series with the Vsus on the SC so it won't go pop if there's a fault. With no panel driven, the output should be usable with a bulb in series.

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

I'm wondering if it's practical to insert a lamp in series with the Vsus on the SC so it won't go pop if there's a fault. With no panel driven, the output should be usable with a bulb in series.

I'm not sure how that would help Tom. I'm not driving the panel at all. It may reduce the current and save me popping it but I feel i've damage other parts of the cct now. The failure points have shifted so much now that its beyond my ability.

Had I not made the first mistake, it probably would have been as easy fix as the other 2.

when i kicked off with this on this board it had the exact same IGBTs failed which makes sense since the buffers were also failed and killed the new board. I recovered that one straight up, was the first board I got going.

Some of these parts I simply can't source cheaply or easily.It's too costly to proceed any further. I've identified pretty much every component but Panasonic have used some fairly unique bits and whilst some you can find a sub for they then use a pckage size that is smaller than the norm just to make it harder again.

Were the first 2 a fluke, maybe a little lucky? I think you just need to nail it first go or else the fault is just heads rampant through the board.

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

Random thought after 5 hours sleep, the other FET driver IC501? Won't know until I get a body bag for all the casualties and strip them from the board.
One of the 100ohm resistors by ic521 is a bit wacky as it's 107 ohms. With current I'm wondering if that's going to drift as it's already out of tolerance. usally they're within 1%

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

Found faulty Diode D702, neither s/c or open.Replaced felt confident, rebuilt the ic521 cct, Q621,622,

failed again sos7, Q661 s/c again, Q621,622 s/c

Purely on a suspicion I removed the 5v IC771, part of the IC773 cct. Gnd-Vin good, Gnd-Vout open cct should get Mohms there.

fail again, sos6, no FETs blown?

Have probed all 35 pins at SC20 in diode mode, all match perfectly with a working board.

[bregva]

Re: Panasonic sc tnpa5081 rebuild

Found faulty Diode D702, neither s/c or open.Replaced felt confident, rebuilt the ic521 cct, Q621,622,

failed again sos7, Q661 s/c again, Q621,622 s/c

Purely on a suspicion I removed the 5v IC771, part of the IC773 cct. Gnd-Vin good, Gnd-Vout open cct should get Mohms there.

fail again, sos6, no FETs blown?

Have probed all 35 pins at SC20 in diode mode, all match perfectly with a working board.

Have I missed some action since I was here last time? That's for shure!

Today I got some parts I was waiting for, but not all, still waiting for extra 30F125's and RJP63F3A's
I started with rebuilding AL board I borrowed parts from. Put back 2 DG502LW, 2 DG402RP and RJP63F3A. Nothing else was taken from this board and it was supposed to be working.
Plugged it with buffers disconnected and SC50 shorted
Got VS 203V for a few moments and then SOS 6.
It did make loud "trrrrr" noise right before sos, like panel was about to come on, even though buffers were disconnected

Checked, couldn't find any blown parts, made shure SC50 was shorted and tried again and again, same sos, 6 blinks!

So here comes stupid question of the day:

Do you connect 4 screws for HV on the buffers while main connectors are disconnected?
I did not, buffers were totally disconnected

OK, next thing I tried to fix my AF board
Plugged it, sos 7, again blown Q661 and this time 30f125's survived but I got blown fast recovery diodes RF2001.
Beforehand, I compared AL and AF but could not find any difference in measurements

At this point I had to go and will try to fix another AF board on Monday

[bregva]

Re: Panasonic sc tnpa5081 rebuild

"Do you connect 4 screws for HV on the buffers while main connectors are disconnected?
I did not, buffers were totally disconnected"

That was really stupid question, I just checked troubleshooting guide and yes they should be disconnected. However I don't see any reasons why flat cable between buffers has to be disconnected also, they are not getting any power anyway!
Will have to check for shorts in 15v and Vda lines, Vs is good, checked already

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

All I know is I'm board weary

just going round in circles now. Finding the bad 5v reg I was hoping to be the missing link.

Messed with so much of the cct now that i don't know if I've done somthing wrong or just have not found what else has failed.

I used SMBTA92 for MMBTA92, BC846 for 2PD601, 2N7002 for 2SK3018. I think they should be ok as substitutes?

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

Here's my road map. I think there's 30 items I've replaced , a little rediculous for no result.

[bregva]

Re: Panasonic sc tnpa5081 rebuild

Here's my road map. I think there's 30 items I've replaced , a little rediculous for no result.

Can you give me reading on D790 from your working board?
In diode measuring mode

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

Can you give me reading on D790 from your working board?
In diode measuring mode

0.185, 1.01, 1290ohms

Anything on the 15v line will drag it down, IC501,521

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

Looks like now that 5v reg is up it's at least stopped blowing the transistors. Has been powered up 4 times now, no blows.

Just randomly swapping parts now, replaced inverter IC563 C14 again, no change.

Then removed comparators IC491,792 NJM2406F. They read different to each other so removed one from a good board to check which was good.

Still no good, back to SOS7 but transistors have still survived.

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

I was wrong with IC491,792

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

IC792 was in fact bad, having trouble probing the pins out of cct, measuring resistance around this it appeared ok but was reacting different on my meter. showed a higher initial reading and slowly went down to the others.
As a result I worked my way through the cct and ended back at IC724 5V reg.

looks like I gave it the quick tick and flick. input resistance was correct 2.6k, output 2.6K! looks like it's been running in bypass mode ramming 15V down the 5V line. This also is feed to the Buffer boards so just as well I've had the buffers isolated testing this.

I get over 2Mohms on the output.

Still no dice though and transistors survived another 3 power cycles.