Panasonic TX-P42G15

[Hombre]

Hi

SC board shorted on this one. It is TNPA4782 (AG).
I already tried once to repair it by changing shorted bits, but it gone short again right after power up. SC50 was jumpered, so none of buffer boards could kill it. Things i've replaced first time were: Q660,661,621,622,421,422,423,441,403. Also q551,702, ic773,464,465,d865. Obviously missed something first time.

So now the IGBT's that gone short are: Q401,402,403,421,422,423,621,622 and Q661.
R707 (3,9k) blown, q701 shorted, ic773, ic562.

Drivers ic501, and 502 look ok, but i will change them both. ic771 com to Vin resistance around 2k, com to Vout around 6k.
5V to gnd resistance is around 620k, and on 15V line resistance is 4.44k which is similar to someone's testing here on the forum (sry can't find the thread but i know i read that somwhere), so that looks promising.

I plan to replace IC561,562,563. IC501,521, Q501,502,521,522,531551.
And all before mentioned shorted things.

Double checked all resistors, just that one blown - R707. Also went through all small transistors, they do seem fine (diode check).

This is the schematic i've been using for throubleshooting: panasonic_tc-p46g15_chassis_gpf12du - can be found on elektrotanya if someone is interested to check it out.

Read at least three times the whole "rebuild tnpa 5081" thread and few similar, helped a lot, and also a lot similarities between all that boards.

So if someone have something to suggest or ask please do, i hope this time this board wouldn't go short again

thx

[tw2005]

Re: Panasonic TX-P42G15

Wow. I have to say that looks like it's heading down the path like the first board I failed , last one fixed and took about 30 components.

Q818 is one I see omitted and was I believe what caught me out. With R707 blown I'm also wondering how far the damage has gone because on mine I ended up with a bad octal buffer IC and also I had to do the nand IC too.

IC691

[Hombre]

Re: Panasonic TX-P42G15

That R707 on my opinion did blow IC562 on mine board (i believe is also octal buffer as on yours board).
I saw that Q818 caused problems to you and some other guys, so i won't push my luck and will simply change it.
Not all parts listed are bad, but will change them, as they are not that pricey.

Anything else i should check?

[tw2005]

Re: Panasonic TX-P42G15

That R707 on my opinion did blow IC562 on mine board (i believe is also octal buffer as on yours board).
I saw that Q818 caused problems to you and some other guys, so i won't push my luck and will simply change it.
Not all parts listed are bad, but will change them, as they are not that pricey.

Anything else i should check?

So what bits have actually failed then?

Which ones were originally faulted and then failed again?

[Hombre]

Re: Panasonic TX-P42G15

On the first fail this is what was bad (maybe some of this were ok but i wasn't sure and replaced them): Q660, 661, 621, 622, 421, 422, 423, 441, 403; Q551, Q702, D865, IC773, IC464, IC465.

Now the IGBT's that gone short are: Q401,402,403,421,422,423,621,622 and Q661.
R707 (3,9k) blown, q701 shorted, ic773, ic562.

[Hombre]

Re: Panasonic TX-P42G15

Ok, update

I changed this parts:
IC501 521 - M81737FP
Q501 502 531 521 522 551 - CPH5524-TL-E
IC464 465 773 - TC7SH14F
IC561 562 - VHCT541A
IC563 - 74VHC14FT
IC691 - TC7SH00FU
IC771 724 - TA78L05F-TE12L
Q701 - 2PD601ART
Q702 - MMBTA92
Q818 - 2SK3018T106
R707 - 3,9k - blew last time

First started tv with both SC2 and SC20 disconnected plus jumper on SC50 - 6 blinks. Then connected SC20 - 7 blinks. Connected SC2 - still 7 blinks. Removed jumper from SC50 and reconnected buffers and installed 4 screws - 7 blinks...
One good thing is that nothing blew this time, no shorts on SC2, survived 2 starts


PS: it is a TX-P46G15 not 42, just noticed that...

[tw2005]

Re: Panasonic TX-P42G15

That's a good sign I guess, that's a point I got to on one of mine. One thing I am curious about was what you were thinking when you had SC2,Sc20 disconnected and jumper on SC50? The SC50 jump is to stop SOS7 detect due to a buffer removed, but you had nothing hooked up to the SC anyway, no power at all.

Anyway looks like 7 blink issue, have a look at IC 561,562 just in case something silly has happened their with the replacement.

was IC561,562 a new parts?

Also does the onboard LED briefly glow before shutdown?

Check R478 4.7k, R500 200ohm,R592 4.7k and D480

On page 30 of the 2009 PDP troubleshooting handbook, there's a resistance check on the outputs to the buffers, can't hurt to check that too.

[tw2005]

Re: Panasonic TX-P42G15

You replaced IC724 but not IC725. Was IC724 bad? If so what did you find with it? was input shorted to output?

[Hombre]

Re: Panasonic TX-P42G15

I was to scared that everything will blow up again, so wasn't very rational at time of that testing

IC561 and 562 are new, i replaced both of them altough just one (IIRC IC561) was bad. Resoldered them - still the same.

Green LED is glowing, interesting?

R478 is 562 and measuring 5.56k so that's good, R592 is ok, so is D480. Don't have R500 on SC board.

One other thing is that 3 resistors around that Q818 are showing some weird values. R673 and R680 which are 4,7k measuring 3.56k, and R777 should be 10k but measuring 4,85k. R776 is 47ohm and it's ok.

IC wasn't shorted, i removed it before and since i have few spare IC's i simply put new one in.
IC724 Vin is 5,52k, Vout 2,98k.
IC725 Vin 5,52k, Vout 5,935k.
IC771 Vin 2,05k, Vout 5,80k.
Does that seem ok?

[tw2005]

Re: Panasonic TX-P42G15

Sorry R590, did not magnify it enough for my eyes. Check resistance between Vin and Vout especially IC725.

Check PC16480 opto pins 1-2 and 3-4

The green LED has more to do with SOS6, curious to see if it lit or not.

Try that SC resistance check too, just trying to find any clues.

[tw2005]

Re: Panasonic TX-P42G15

Sorry also meant R476

[tw2005]

Re: Panasonic TX-P42G15

I have another idea,connect the SC up without the buffers, Sc50 jumped. find D480 and measure voltage at the anode as SOS7 trips. I think 4-5V, if nothing there, repeat on the cathode side.

Should be able to work out which part of the SOS7 cct is triggering the shutdown(hopefully) and go from there.

[Hombre]

Re: Panasonic TX-P42G15

First sry for delay, some things had to be done

Those resistors are ok, r592 and r476.
Tried this idea with sos7. D480 anode 0V, cathode 4,5V. Went further and measured voltages on D820. On anode that is connected to R752 and Q876 i have 4,5V. Second anode measuring -0,75V.
D875 - cathode 15V, anode 0V.

Tested voltages:
VAD -185V
VSCN -40V
VSUS 201V
5V OK
15V OK

[tw2005]

Re: Panasonic TX-P42G15

So looking like a VSCN issue, is that your conclusion? I'm still analysing the info you have but good work , your obviously thinking ahead there. If we know the path of the detection hopefully lead us to where it's faulty.
Frustrating, feels like your real close to getting it running if it's no longer going up in smoke.

[tw2005]

Re: Panasonic TX-P42G15

Actually, cancel that VSCN is meant to be-40v , and you say 15v is good so does that mean something there like Q876 is dud? How are the diodes all around there?

[Hombre]

Re: Panasonic TX-P42G15

Checked resistors and diodes there and everything is in specs. Q876 had some strange measuring and since i had new 2PD601AR (needed for Q702 - bought 5 pcs) i simply replaced it. Readings after that were better.
So put SC board in, tested buffers once again, just a precaution. Powered set with SC50 jumpered and buffer disconnected - blinking green led went in to solid green
Reconnected buffers and voila - tv is on like it never was broken before

Thank you TW, i doubt i could solve this without your help!

[tw2005]

Re: Panasonic TX-P42G15

Checked resistors and diodes there and everything is in specs. Q876 had some strange measuring and since i had new 2PD601AR (needed for Q702 - bought 5 pcs) i simply replaced it. Readings after that were better.
So put SC board in, tested buffers once again, just a precaution. Powered set with SC50 jumpered and buffer disconnected - blinking green led went in to solid green
Reconnected buffers and voila - tv is on like it never was broken before

Thank you TW, i doubt i could solve this without your help!

Nice, after I saw all those voltages were correct I had a strong feeling that if you had earthed the SOS7 line then it would have fired up but there was no way I was going to suggest it after all the hard work.

It has been done before to prove a theory but this is the first time I've put a lot of thought into that part of the cct.

must say nice fault finding and teamwork here. This will be a good future post and give people some hope and confidence and some good honest logical fault finding.

I must say I enjoyed sharing the journey, you knew exactly where I was heading and post very clear and accurate info.

All looks quite simple now looking back at it LOL.

Good thing too is this is a TNPA4782 and I'm sure there'd be a few people wanting to repair their boards and fixing any size TV 4782 should be similar .

[tn245]

Re: Panasonic TX-P42G15

Hi! Great to hear a success story on this sc board. I'm just now tackling a TNPA4782 (AB) from a 50" set. The seller turned it on and showed me it doing 7 blinks. When I got it open I found three IGBTs already desoldered and hanging off their heatsink screws so not sure what further damage booting it up in that state may have done.

Components that I've found that seem to be definitely bad or a little suspicious are:
Q601
Q661
Q441
Q701
Q551
IC464
IC465
IC561
IC562
IC563
IC501
IC521
IC771
IC773
D608
D618
R551
R613
R707

Seems to be a different failure pattern than Hombre's. Any other bits I should double check given what's in the above list? I think I've checked all the usual suspects based on reading this thread and the other panasonic sc threads, but it would be useful to have the forum's opinion before putting in the parts order. I'll be ordering extra in case it doesn't go right first time.

[Hombre]

Re: Panasonic TX-P42G15

Q702 is often one of usual suspects too
And maybe this: Q501 502 531 521 522 551.

Wait for tw2005's answer

[tn245]

Re: Panasonic TX-P42G15

Thanks Hombre. Good call on Q702. Although it wasn't shorted I took another closer look at it and there is a small hole in the top.

Q551 was in my list and is shorted between all pins. The others Q501 502 531 521 and 522 I was suspicious of. They are not shorted and no signs of damage but I did just now take resistance readings in-circuit. Based on other threads I understand pins 1-5 and 2-3 should be in Mohms but mine are reading in Kohms or jumping about so I guess I'd better replace them all.

What about ic691? No shorts or damage but I have R707 blown too. How do you test this one?

Hoping for some input from tw2005 too.