PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

[tw2005]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

Just had a go at doing a quick repair of this TNPA5066.

Q661 shorted on 2 legs
D451 shorted
D481 shorted
Q702 shorted
IC773 bad, resistance pins 3-4 128ohms, good reads over 2Mohms
Q818 seemd ok in cct but replaced with 2N7002

Q701 seemed ok and left

Looking all good and similar to what I've done on the 5081.

And, bang

Now, it's really bad just like the last time I got it wrong.

Q701 shows short. maybe I missed testing or mistested this, that I'll never know now.

So, Q661 again dead, Q818 shows short, R707 blown, Q702 short, D701 short

Now in cct Q421 short, D421 short, D401 short, Q402 short, Q401 short,

IC771 5v reg now showing shorted output, that powers the inverter IC but was not shorted originally.

[tw2005]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

I have a feeling I may have tested the wrong transistor for Q701.

So confirmed bad.

R707,Q701,702,818,661 IC773, possibly Q672

Q401,Q402

IC562 , because R707 flashbanged, that's connected to pin 17 and last time I had bad R707, IC562 was bad.

Not sure if I'll persist with it or not because the Tv is working, just waiting on the correct SS board to arrive.

[flocko]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

Hi TW sorry to hear that, i now have all my parts to hand for my repair but was giving myself a bit more time before starting it.i will now double check every thing before i make my move.Your work will not be in vain and thanks again for all your help (those Ebay boards are sure looking tempting now) Flocko

[tw2005]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

Hi TW sorry to hear that, i now have all my parts to hand for my repair but was giving myself a bit more time before starting it.i will now double check every thing before i make my move.Your work will not be in vain and thanks again for all your help (those Ebay boards are sure looking tempting now) Flocko

My replacement boards arrived, nothing shorted on them so should be good.

So looks like I have a spare good SN for comparison.

100% sure your IC773 is bad. So have a good look at the schematic. IC771 the 5V reg now has a low resistance on the output. I've removed it and tested it as good put 15v in and produces 5.07V out.

I suspect the opto PC16461 is now damaged which is going to be hard to work on because of the overhang of the heatsink.

[flocko]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

Checked with the seller of those boards asked if they did not work could i return them, he told me they were from a set that had a cracked screen, but the set powered on and showed a mucked up picture and were half the price of the rest on ebay but would not take returns, i asked if he would test them for shorts and his reply was i dont now how? so back to the repair will get the board out and start checking it over as per your list of parts later today,i am having a job to find the 5v reg IC 771 and the opto PC16461(461) on my board?

[tw2005]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

Checked with the seller of those boards asked if they did not work could i return them, he told me they were from a set that had a cracked screen, but the set powered on and showed a mucked up picture and were half the price of the rest on ebay but would not take returns, i asked if he would test them for shorts and his reply was i dont now how? so back to the repair will get the board out and start checking it over as per your list of parts later today,i am having a job to find the 5v reg IC 771 and the opto PC16461(461) on my board?

well if you're following a service manual which I hope you are, it's quite simple.

To locate in the schematic use find and use the full identifier IC16771, to get the board location drop the 16.

It's a SMD 3 pin device marked AE right next to the Sn2 connector, the opto is to the right , 8pin in front of the large heatsink.

sounds like those boards maybe ok if it powered with no blinks but powering it up with a cracked screen and possible short is a bit risky.

getting it right first time for repair is the challenge, I must have had a brain fart on mine because it appeared no harder than the 5081 I've done.

But the extra damage sure looks familar so I still believe the inverter cct that drives Q661 is critical.

That's Q701,702,818,D701,702, IC773,IC771, maybe shunt reg cct Q672,662,663 etc

Either D701 or 702 intially showed short but cleared once I removed the shorted components around it.

[flocko]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

Hi sorry just had the board in front of me and not looking at the schematic just around the top of the board near the other parts Q701/2 IC733 thinking must be round here some were? it will happen to you when you get to my age, any way just got my meter out and started testing IC 773 showing 113 ohms across pins 3-4, i went to test Q818 in diode mode and i think my battery must be on its way out as meter keeps showing full screen ever thing comes on as soon as you put the probes on any thing it was playing up the other day. so off for new battery Flocko

[tw2005]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

Hi sorry just had the board in front of me and not looking at the schematic just around the top of the board near the other parts Q701/2 IC733 thinking must be round here some were? it will happen to you when you get to my age, any way just got my meter out and started testing IC 773 showing 113 ohms across pins 3-4, i went to test Q818 in diode mode and i think my battery must be on its way out as meter keeps showing full screen ever thing comes on as soon as you put the probes on any thing it was playing up the other day. so off for new battery Flocko

yeah, I understand. my eyes are crap for this tiny work. The other check is 3-5 gnd-vcc but you'll have to remove IC773 and recheck IC771 anyway. i think 5.6k is the norm but you'd want to be sure the reg is good .

must be that time of the month , my low bat is showing too but still reading ok.

[flocko]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

Not just my eyes thats gone but thats another story, Was just going to check every thing and get some before and after replacement readings,as when i replace SMD transistors like these i cover them with solder to get them off the board as quickly as i can, but testing them after in most cases will not give a 100% reading with all the heat that has been put though them, Flocko

[tw2005]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

For what they cost, really just as safe to replace them. Q818 I've had one bad not go short, 701,702 I find will be short. It will be interesting to see your list of suspects that show short.

[flocko]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

did you end up changing Q603 as i cannot see it listed on the parts you have listed as having failed

[tw2005]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

did you end up changing Q603 as i cannot see it listed on the parts you have listed as having failed

no, that's a SMD transistor? Mine seems ok

[tw2005]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

....................So got another board (SS) - fixed!

So lesson here was using what I thought was a reasonable substitute IGBT, IRG7S313UPBF caused me grief (not proven yet ) RJP30E4 were the originals............................

So I've revisted my old SS to investigate why the IGBT replacement did not work.

looks like those substitutes would work because I just swapped the RJP30E4 IGBTs from the wroking 50" board onto it and same problem.

So I'm left wondering now where to look but I'm thinking maybe sustain control and maybe damaged octal buffer.

So I swapped one of those and still the same.

Mystery but I think this is where I leave it.

[tw2005]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

So I've revisted my old SS to investigate why the IGBT replacement did not work.

looks like those substitutes would work because I just swapped the RJP30E4 IGBTs from the wroking 50" board onto it and same problem.

So I'm left wondering now where to look but I'm thinking maybe sustain control and maybe damaged octal buffer.

So I swapped one of those and still the same.

Mystery but I think this is where I leave it.

Seriously, Who am I trying to kid.I can't be beaten now can I? Nothing learnt.

I could not find a single discrepancy with the semiconductors which really had be baffled.

I was thinking half the signal was missing or the like via IC241 which I hate trying to solder by hand, but as I mentioned no change there.

So in a last effort out of frustration all I could come up with was maybe something simple as a resistor was open cct. Apart from around the blown IGBTs i had not really checked them all, did not see much point.

The FET driver IC, I replaced just in case so very confident that was ok.

I start measuring across tiny resistors starting at the signal end, all checking good so far. each time comparing with the good board.

I get to R131, R132 tiny 100 ohm resistors which AA_UMH & AA_UML enter the fet driver at HIN & LIN or from what the waveform is generated.

On the good board 100ohms a piece, on my board R132 100ohms, check, R131? R131, where the f is my R131?

So I had no drive signal on HIN!

So, for about 12 months I've had this POS collecting dust deciding whether to keep going or what.

The truth is out, those substitutes would have worked, because there was nil change putting the original type in.

Clearly when I was working on the FET driver IC, I must have had the iron resting on R131 and desoldered the little bastard.

[tw2005]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

My replacement boards arrived, nothing shorted on them so should be good.

So looks like I have a spare good SN for comparison.

100% sure your IC773 is bad. So have a good look at the schematic. IC771 the 5V reg now has a low resistance on the output. I've removed it and tested it as good put 15v in and produces 5.07V out.

I suspect the opto PC16461 is now damaged which is going to be hard to work on because of the overhang of the heatsink.

I can confirm the low 800ohm across 5V out of IC771 was due to the opto now blown. That's a bugger because it's not readily available, can't find a single datasheet, I know it's a NEC PS9856-2-F3-AX . Last time I had to get someone to buy it direct in the US and forward it which made it expensive.

[flocko]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

So the moral to this story is dont just look at what is there but also look for what is not there , well done so now you have lots of good SN and SS board true Panasonic gold dust well they are over here name your own price. i could box my ones up and send to you, would give you something to do now your on top of the game, help keep your hand in as it were(i joke) anyway well done mate nice one Flocko

[tw2005]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

So the moral to this story is dont just look at what is there but also look for what is not there , well done so now you have lots of good SN and SS board true Panasonic gold dust well they are over here name your own price. i could box my ones up and send to you, would give you something to do now your on top of the game, help keep your hand in as it were(i joke) anyway well done mate nice one Flocko

Cheers, I think when logic tells you it should be working and it's not, you have to start thinking out side the square.

I simply dont have the refined gear sometimes when things get tight and small.

The irony is, the FET driver I believed was ok but I had one I knew was ok so decided to swap it. If I had left it, that resistor would still have been there.

I only got the extra SN,SS and C boards as a last ditch. I'd touched all of those to do component repair and assumed I'd missed something.

It was my fault that I ended chasing my tail. I did the same thing when i rebuilt the A board. nearly lost a small resistor there and bridged some others creating 9 and 13 blink.

I will say this, to come out the other side with it working as it should is a small miracle. Learnt heaps and very rewarding.

I prefer to fix these cheap as I can, but I also like to show what can be achieved out of the norm especially with A boards.

So it's a good example if you can find an A board the same series and build, a swapping eeproms and flash Ics will simply give you the original configuration of your TV.

[flocko]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

hard to get any diode mode test to make much sense ,i have taken them but i think just to confusing for me anyway, so i just went for a good old 200 ohm continuity test this is what i found Q818 D-S =OL/ D-G=OL/G-S=OL So all open,Q701 C-E=27 ohm/C-B=OL/ B-E=OL so not dead short but short just the same Q702 C-E=OL/C-B+OL/B-E=short, Q603 C-E=OL/C-B=OL/B-E=OL and with IC773 showing low ohm across pins 3-4 my parts list for this is D481 D401,Q661, Q701, Q702 and IC773, so not that much between them,now for the SS

[tw2005]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

setting 200ohms and looking for short is ok if expecting a short but what if something is not but low ohms? If you have a replacement foe Q818 I'd fit it. Check resistance is 5.6k gnd to output of IC771 or vcc to gnd on IC773.

[flocko]

Re: PANASONIC plasma TH-P42X20A, SOS4,1,10,6,8

Well here they are in diode mode readings for Q818 + on first test point D-S=1.770 D-G=!.80 S-G=.286 S-D=.719 G-D=.824 G-S=.208 as i said not much sense to be made of that i have all the parts to change and was going to