Panasonic P42G20ES

[Mtgtnt]

Re: Panasonic P42G20ES

Unfortunately it doesn't. But it does display 000 for closed circuit.

[tw2005]

Re: Panasonic P42G20ES

I have finished testing all pins of SM41/42/46. All were out of range except SM41 pin 4 and SM42 pin 2. Those were exactly 220k.
Some took a while to go out of range, while most were oor right away.

http://youtu.be/NQtSXVgTUIg

From the few boards I've seen bad , Vfo usually goes short, Vscn-f I've seen short and 5V-f ends up much lower in resistance in K ohms.

Unless you can get a better meter that's about as good as you can failing trying to measure resistance at each output looking for shorts.

personally, I would use this board.

[tom66]

Re: Panasonic P42G20ES

Unfortunately it doesn't. But it does display 000 for closed circuit.

Yeah, I'd go with what tw2005 is saying... it's not going to be easy to test with that.

[Mtgtnt]

Re: Panasonic P42G20ES

Thank you both for the help. Once the replacement board gets here, I will let you all know how it goes.

Should I test without SM board hooked up first?

[tom66]

Re: Panasonic P42G20ES

Yes, connect board up, jumper SC50 on SC board, the TV should turn on without a picture and no error codes. (green solid LED)
That will confirm it is not tripping an error, should then be ok to hook buffers to board.

[Mtgtnt]

Re: Panasonic P42G20ES

Yes, connect board up, jumper SC50 on SC board, the TV should turn on without a picture and no error codes. (green solid LED)
That will confirm it is not tripping an error, should then be ok to hook buffers to board.

I jumped SC50, turned on the tv. No error code then poof, buffer board went up in smoke. SC41/42/46 were not connected. But I did have buffer board screwed in.

Guess im now looking for replacement SM board. SC board is fine.

This will have to wait until after Christmas.

[tom66]

Re: Panasonic P42G20ES

You can't connect the buffer without the other connectors. That is why it failed. YOU MUST connect all of them at once.

[Mtgtnt]

Re: Panasonic P42G20ES

You can't connect the buffer without the other connectors. That is why it failed. YOU MUST connect all of them at once.

So in this step,
"Yes, connect board up, jumper SC50 on SC board, the TV should turn on without a picture and no error codes. (green solid LED)
That will confirm it is not tripping an error, should then be ok to hook buffers to board."
I should have had the 3 connectors also connected to the buffer board and the jumper on SC50?

If so, lesson learned the hard way.

[tw2005]

Re: Panasonic P42G20ES

Sadly, you had the procedure. Either of those guides had it but in the 42S2 guide (slide 94).

Bugger!

"To isolate the SM board is not necessary to remove any boards:
Remove the 4 VF_GND screws on the SM board.
‰Unplug connectors SC41, SC46, and SC42 on the SC board.
‰Place the SC jig cable (TZSC09187) between pins 1 and 2 of connector SC50 on the SC board."

looks like I've danced with the devil. pretty sure I've tried it with the screws left in (maybe I'm mistaken) and got away with it once or twice but i always follow the procedure these days. Often wondered if it was really necessary, I guess you proved it is>

[Mtgtnt]

Re: Panasonic P42G20ES

I was able to talk to a local tech back home about the TV (old neighbor that been in the radio and tv repair for over 30 years). He said that it is possible that a short happened on the SM board and that fried the SC board. With the old boards still connected, the short that was created in the SC board kept the SM board from completely frying.

He asked if I isolated the SM board (SC41/42/46) with all screws in place while the old SC board was still in the TV. Since I did not he cannot say that the short was started in the SM board.

So his final thoughts were that once I installed the working SC board and did not connect SM to SC and only did the jumper, the current passing through the SM board had no where to go and finished frying itself. Which is good he said as if I had hooked it up I could have fried the new SC board.

So the procedure in the manual is probably correct.

[tw2005]

Re: Panasonic P42G20ES

I was able to talk to a local tech back home about the TV (old neighbor that been in the radio and tv repair for over 30 years). He said that it is possible that a short happened on the SM board and that fried the SC board. With the old boards still connected, the short that was created in the SC board kept the SM board from completely frying.

He asked if I isolated the SM board (SC41/42/46) with all screws in place while the old SC board was still in the TV. Since I did not he cannot say that the short was started in the SM board.

So his final thoughts were that once I installed the working SC board and did not connect SM to SC and only did the jumper, the current passing through the SM board had no where to go and finished frying itself. Which is good he said as if I had hooked it up I could have fried the new SC board.

So the procedure in the manual is probably correct.

Hopefully you can find a SM fairly cheap, at least the used board proved ok. still will be cheaper than that crazy repair quote.

It's actually the Sc board that fails in these, buffer failure is fairly rare.

It was most likely the Vfg screws, it's floating gnd not the same as chassis.

All academic now, but it will reinforce to make sure those screws are out on that test.

I was giving it some thought and I think the only time I may have forgotten to take those screws out was on a dead SC board anyway and it would have been already fitted. probably why I got away with it.

I've frequently done that test for my repaired boards so i know I've never put the screws in putting a sc in on it's own and having read the guide never will. So probably when I first touched my TV I knew very little and did not have the guide back then.

Have you done an autopsy on the old SC yet?

[tom66]

Re: Panasonic P42G20ES

There is no easy way for the short to "go through" the buffer board, as the plasma panel is an isolated capacitor. The risk comes when the board has some parts grounded and other parts connected to Vf without the low voltage supplies (5V) connected.

This fries the board... same reason as why you should not plug Va connector into plasma panel while it is running, as it is not designed to have the supply voltage come up is the wrong order.

[Mtgtnt]

Re: Panasonic P42G20ES

I am back.

Replacement SM board here.

Installed everything, 7 blinks.
Did resistance check on P board, all good.
Removed SC20, changed to 6 blinks.
Isolated SM board, jumped SC50.
Replaced SC20, back to 7 blinks.
LED D583 does light on this SC board where previous board did not.
But I'm guessing that this SC board is also no good.

Anyone have a step by step on how to find what is wrong with either SC board or do I just try and get a refund?

[tw2005]

Re: Panasonic P42G20ES

I jumped SC50, turned on the tv. No error code then poof, buffer board went up in smoke. SC41/42/46 were not connected. But I did have buffer board screwed in.

Guess im now looking for replacement SM board. SC board is fine.

This will have to wait until after Christmas.

How did you reach conclusion SC was still ok after SM blowup

I am back.

Replacement SM board here.

Installed everything, 7 blinks.
Did resistance check on P board, all good.
Removed SC20, changed to 6 blinks.
Isolated SM board, jumped SC50.
Replaced SC20, back to 7 blinks.
LED D583 does light on this SC board where previous board did not.
But I'm guessing that this SC board is also no good.

Anyone have a step by step on how to find what is wrong with either SC board or do I just try and get a refund?

Refund might be tricky since it was ok to start with.

I should be able to get you on track to component repair it.

Disappointed to hear this has not worked out.

Is Q661 shorted ?

[Mtgtnt]

Re: Panasonic P42G20ES

Here is a list of "Q" and "D" that are shorted:
Q661
Q621 20ohms

D641
D642

[tw2005]

Re: Panasonic P42G20ES

Here is a list of "Q" and "D" that are shorted:
Q661
Q621 20ohms

D641
D642

Once you've decided you're going component level on this and not returning the board, then remove Q621 and 622, recheck associated diodes. you know these are common cathode A-K-A so outer legs will show short A-A.

[Mtgtnt]

Re: Panasonic P42G20ES

Yes, it was shorting across K-A.

While I am pulling these from the new board to test and from the old board for possible replacements, should I be looking for anything else?

[tw2005]

Re: Panasonic P42G20ES

Yes, it was shorting across K-A.

While I am pulling these from the new board to test and from the old board for possible replacements, should I be looking for anything else?

most definitely. I just need to feel confident you're on the ball, sounds like you are. Plenty brush through , jump in, fail and then go back to where I suggest only to find they've missed a shorted IGBT.

So to keep things clear, I need to know whether in cct or not for those diodes as i find those ones survive and once the 30F125 are removed are ok but i will have to spend some time sifting through my other thread for results. I think I'll have to start collating in excel for quick ref. i have had a board with very little replaced, i think 7 parts in toatl. that's my lowest count so far, usually more.

i'll get a photo of the 42' and circle the bits i know have failed. with Q661, these need to be checked and i'd suggest replacing regardless.

IC773, Q701,702,818,

check d702, check ic771, check PC461

Have you got the schematic for the SC board?

[tw2005]

Re: Panasonic P42G20ES

some resistance checks i had saved

[Mtgtnt]

Re: Panasonic P42G20ES

...
i'll get a photo of the 42' and circle the bits i know have failed. with Q661, these need to be checked and i'd suggest replacing regardless.

IC773, Q701,702,818,

check d702, check ic771, check PC461

Have you got the schematic for the SC board?

Will check all those you listed.
panasonic_tx-p42g20e_es_tx-pf42g20s_tx-pr42g20_chassis_gpf13de
This pdf do?