Panasonic TC-P50G25: SD/SU Resistance Test

[svc]

I have a Panasonic Troubleshooting Handbook for this model that describes some resistance tests for the SU and SD boards. I am getting some...different...readings than specified, but none to indicate a short circuit.

For my SU board, I read infinite (more than 50Mohms, anyway) between the TPSU18 ground test point and TPSU15, TPSU16 and TPSU17. When I used the pad around where the VF Ground screw would be (my SC board is currently removed for me to rebuild) I have these readings:

VF Ground to TPSU18: Infinite (> 50Mohm) which is odd since it is the same point, no?
VF Ground to TPSU15 (Vfo): 476Kohm - manual says I should get 2.2Mohm
VF Ground to TPSU16 (VSCN-F): 220Kohm - approx. correct
VF Ground to TPSU17 (5V_F): 729Kohm - manual says I should get 5.7Mohm

I get the same kind of funny business with the SD board:
VF Ground to TPSD26 (5V_F): 643Kohm - manual says I should get 5.7Mohm
VF Ground to TPSD28 (VSCN-F): 220Kohm - approx. correct
VF Ground to TPSD29 (Vfo): 475Kohm - manual says I sohuld get 2.2Mohm

Do these readings indicate faulty SU and SD boards? The boards are 5090 and 5091, respectively.

Thanks in advance!

[tw2005]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

I have a Panasonic Troubleshooting Handbook for this model that describes some resistance tests for the SU and SD boards. I am getting some...different...readings than specified, but none to indicate a short circuit.

For my SU board, I read infinite (more than 50Mohms, anyway) between the TPSU18 ground test point and TPSU15, TPSU16 and TPSU17. When I used the pad around where the VF Ground screw would be (my SC board is currently removed for me to rebuild) I have these readings:

VF Ground to TPSU18: Infinite (> 50Mohm) which is odd since it is the same point, no?
VF Ground to TPSU15 (Vfo): 476Kohm - manual says I should get 2.2Mohm
VF Ground to TPSU16 (VSCN-F): 220Kohm - approx. correct
VF Ground to TPSU17 (5V_F): 729Kohm - manual says I should get 5.7Mohm

I get the same kind of funny business with the SD board:
VF Ground to TPSD26 (5V_F): 643Kohm - manual says I should get 5.7Mohm
VF Ground to TPSD28 (VSCN-F): 220Kohm - approx. correct
VF Ground to TPSD29 (Vfo): 475Kohm - manual says I sohuld get 2.2Mohm

Do these readings indicate faulty SU and SD boards? The boards are 5090 and 5091, respectively.

Thanks in advance!

I test mine at the connectors. Try it again and also reverse the probes around if you cant get it. Vfo - gnd you should be able to get the correct reading. Most of mine are around 1.8-1.9meg.

Can you post a copy of the test procedure you're following from the manual

[tw2005]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

Did you see the chart in post #58?

https://www.badcaps.net/forum/showth...t=26322&page=3

[svc]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

My Vfo -> ground reading is just under 500k. Guess I need new boards. Test procedure is attached...on slides 43/44

I must have skimmed past post 58. For reference, here are my results at the connector (strange that they're different...) :

SU:

Red on ground, black to pins:
1 - OL
2 - 574k
3 - OL
4 - 220k
5 - OL
6 - OL
7 - OL
8 - 300k
9 - OL

Black on ground, red to pins:
1 - OL
2 - 479k
3 - OL
4 - 220k
5 - OL
6 - OL
7 - OL
8 - 730k
9 - OL

SD:

Red on ground, black pins:
1 - 710k
2 - 219k
3 - OL
4 - OL
5 - 289k
6 - 289k
7 - 413k
8 - 300k
9 - OL

Black on ground, red to pins:
1 - 480k
2 - 219k
3 - OL
4 - OL
5 - 660k
6 - 660k
7 - OL
8 - 632k

[tw2005]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

Hey, that's fantastic you have that guide. Even validates my measurements I posted which is good because I was unsure about 5V_F.

I would treat your boards as bad if you can get close in meg ohms for those you have kohms for.

It's not worth damaging another SC.

I'm and probably some others would be interested in knowing where you scored that training guide. I've looked a few times now at http://elektrotanya.com/ which is prettygood with info.

What else do you have that you could share. Tom web hosts most of his stuff.

[svc]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

I found that through Google! Along with the two other documents I attached. One I think I grabbed through some random forum and the other (along with the previously linked one) were actually straight from Panasonic's website.

I picked up two 'broken' plasma TVs from the classifieds after I fixed my sister's TV by soldering two new caps to two standoff boards of a 42" TV's power supply (MC201 and 301) and thought "wow I can do this." Pffffffffffffffft WRONG. So I've just recently adopted this as a hobby and don't have any real collection of material or knowledge of the matter. I studied electricity in university but there's a pretty big gap between theory and how to use it to fix televisions...

Is it work looking into the SU/SD boards to fix, or should I just grab new ones?

Thanks again for all the advice. Let me know if you could ever use some help in finding a guide and I'll see what I can do!

[tw2005]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

Unless you have hot air and can get the buffer IC then no. I don't and I can't. I have 2 standard soldering irons and a fluke. Not exactly high end professional stuff.

Buffer boards are usually not too bad to get but will only get worse as more of these fail and stocks of damaged TVs get exhausted.

I would hang on to those and compare if you get replacements but you never know down the track there may be no choice but to rebuild these.

Already see this with 2007 Samsung plasmas where these buffers fail all the time and are now hard/expensive to get and places are starting to rebuild.

It will cost a lot more to attempt to get the Ics and rebuild than the boards, but unless you get the SC going or replace you won't be needing them.

Google, I've tried that trick, usually pretty good at it too. Looks like i should have tried different keys words.

Your the first to find it though here, it really helps when you have the correct guide especially for those buffers, now people can trust my figures but also have a legitimite procedure to follow so I don't have to feebly explain it.

hang around here if you're interested in this type of hobby work. Sounds like you' have a taste for panasonic stuff. I'm biased towards them too but will dabble with most stuff except LCD..

Unfortunately where i am now it's rare to get a dud set to fix, so i stalk around here and have my two bobs worth, sometime I get it right, sometime I'm completely offtrack.

Tom's a regular, not much he can't nut out . Quite a few other regualrs too that get into the Panasonic gear. I read this week it's all over at the end of the year for panasonic plasma. looks like I better learn more about LCD then,

[tw2005]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

Actually I just had a look at the file name on that guide. looks like that may have been just released Oct2013, 101013 is usally the date stamp going on how they mark the other guides,probably why we have not seen this till now.

[tw2005]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

Hey, that's fantastic you have that guide. Even validates my measurements I posted which is good because I was unsure about 5V_F.

I would treat your boards as bad if you can get close in meg ohms for those you have kohms for.

It's not worth damaging another SC.

I'm and probably some others would be interested in knowing where you scored that training guide. I've looked a few times now at http://elektrotanya.com/ which is prettygood with info.

What else do you have that you could share. Tom web hosts most of his stuff.

hey I've left out a single important word "not"

Correction:I would treat your boards as bad if you can not get close in meg ohms for those you have kohms for.

I figure you knew that, just in case somone else gets the wrong idea.

[svc]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

Well lucky me then! To be honest, two weeks ago the only thing I'd ever done to a TV was turn it on and adjust the volume. I've since fixed a 42" successfully, am confident that the IGBTs I have en route will fix a 50" and it seems like my second 50 is going to be a pet project for months to come.

I don't have any equipment fancier than that...save for a logic analyzer that is probably of no use unless CAN or I2C comms show up. I've soldered an 80 pin IC before by hand and that made me want to quit school and become a Broadway Musical star. Not that there's anything wrong with that.

I like this forum. The amount of knowledge and experience is epic and the fact that it isn't intimidating makes it even better. I have a degree in electrical engineering but I haven't been out of school long enough to have learned anything useful in this respect. All this stuff is a big black box I'm trying to figure out and testing faulty components in place is a brand new concept.

I've always been slightly biased towards everything Panasonic but this endeavour into Panasonic repair is a fluke of my sister and her husband having purchased one. Hopefully other manufacturers have trouble codes that make diagnosis so easy...then LCD/LED units shouldn't be *too* different

[svc]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

hey I've left out a single important word "not"



I figure you knew that, just in case somone else gets the wrong idea.

Yeah I caught that! Would have been worse if you had said "It's worth damaging another SC"

[tw2005]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

this endeavour into Panasonic repair is a fluke of my sister and her husband having purchased one. Hopefully other manufacturers have trouble codes that make diagnosis so easy...then LCD/LED units shouldn't be *too* different

I got into this when a mate brought his 2007 42" in to fix at work and failed several attempts so I told him whenever he had enough not to bin it and give me the remnants. had it working the first night I had it home and been hooked on them since.

Only this year I got really bored and frustrated enough to have a crack at rebuilding the Sc board but since I own the TV for these I have good reason to stock some spares.

the more i see with parts availability and the throw away approach we have these days the beter ifeel about it because supply is drying up and manufacturues are not terribly interested in supporting their product for too long.

I often wonder how many repairable boards have gone to landfill. You could not make a living out of it, but so rewarding.

Most people when they find out how much repairs are just toss the TV.

I'm yet to have someone use the info in my thread and report a success, but I'm sure some of the repair ads you see are possible a result of the huge information you find in here because of all those who passionately do this whether beginner/hobbyist or pro.

Best forum I've ever found.

[svc]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

I will certainly report back with my status on the SC board rebuild! Most items on your list I have verified as bad so hopefully mine isn't any worse.

I moved the TV while vacuuming today and a quick glance has posed another question. There are several fuses on the P board...while I (think I) verified it not to be bad, all the fuses measure as short circuited. I've never seen a fuse with coloured stripes and haven't had any luck finding a replacement part or even any specs. Thoughts?

And I second that...best forum I've found.

[tw2005]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

A shorted fuse is a happy fuse otherwised it would have fused and be open which is the job of a fuse on overcurrent.

Highly doubtful there'll be a problem with the PSU.

[svc]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

I can't believe I forgot how a fuse works...biggest brain fart I've ever had...

[tw2005]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

I just had my morning coffee, I'm good for 5 mins.

[svc]

Re: Panasonic TC-P50G25: SD/SU Resistance Test

That was after 4pm in the afternoon for me. Can I edit a post on the basis of not looking like a fool? I promise I understand the concept of a fuse...