Panasonic sc tnpa5081 rebuild

[tom66]

Re: Panasonic sc tnpa5081 rebuild

I don't see anything massively shorted so it might be OK. Could be that your meter cannot read >2Megohm.

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

The SC came in today and tests good with SC50 jumpered but I've apparently got two bad buffers.

SU41
1 OL
2 OL
3 OL
4 218.4kohm
5 OL
6 OL
7 OL
8 1.54Mohm
9 OL

SD42
1 OL
2 217.5kohm
3 OL
4 OL
5 6.+Mohm
6 6.+Mohm
7 21.7Mohm
8 6+Mohm
9 OL

My results could be a bit flaky, some of those are variable and react differently depending on the polarity and if any charge has already been put in by the probes. try again with black probe on the gnd .

Main thing is you don't want shorts or much lowerthan normal readings.
They could be ok but no measurement on VFO is strange.

I've only seen so far either short there when bad or what I have below.

SD42 pin 1 VFO you definitely should see something. Try again and both polarities.

I get 5.3M & 1.88M

SU41 pin 2 VFO 5.27M & 1.98M

pin 8 try again both polarities it's quite variable. One of mine showed 1.5M but rose to 6.3M & 2.03M in reverse

[johnboy1313]

Re: Panasonic sc tnpa5081 rebuild

I tried both polarities and I don't remember a difference. I'll check again when I get a chance.

[johnboy1313]

Re: Panasonic sc tnpa5081 rebuild

With the polarities swapped

SU41
1 OL
2 6.8 Mohm
3 OL
4 219.8 kohm
5 OL
6 OL
7 OL
8 Starts low and quickly ramps up to OL
9 OL

SD42
1 6.7 Mohm
2 217.5 kohm
3 OL
4 OL
5 Starts low and quickly ramps up to OL
6 >30 Mohm
7 OL
8 >30 Mohm
9 OL

I probed all SU41 and SD42 again with red on the ground pan with the same results that I saw yesterday.

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

With the polarities swapped

SU41
1 OL
2 6.8 Mohm
3 OL
4 219.8 kohm
5 OL
6 OL
7 OL
8 Starts low and quickly ramps up to OL
9 OL

SD42
1 6.7 Mohm
2 217.5 kohm
3 OL
4 OL
5 Starts low and quickly ramps up to OL
6 >30 Mohm
7 OL
8 >30 Mohm
9 OL

I probed all SU41 and SD42 again with red on the ground pan with the same results that I saw yesterday.

Well at least you now have a reading on the VFO pins, nothing shows short so I'd used them.

[johnboy1313]

Re: Panasonic sc tnpa5081 rebuild

Ok. What have I got to lose?

[tom66]

Re: Panasonic sc tnpa5081 rebuild

You could kill the SC...

[johnboy1313]

Re: Panasonic sc tnpa5081 rebuild

It's working! I had to reseat a couple of the panel ribbons but she works like a charm. I think this one has internet apps.

[johnboy1313]

Re: Panasonic sc tnpa5081 rebuild

You could kill the SC...

I was being sarcastic.

[tom66]

Re: Panasonic sc tnpa5081 rebuild

Nice fix. Gotta keep an eye out for one. Would look real nice in the living room. Already got an older 46" Panny but.......

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

It's working! I had to reseat a couple of the panel ribbons but she works like a charm. I think this one has internet apps.

With mine (TH-P50V20A) I had no internet features in Australia until I did the latest frimware upgrade.

http://panasonic.jp/support/global/c...down_navt.html

That should be the link for yours.

[johnboy1313]

Re: Panasonic sc tnpa5081 rebuild

I connected mine to the net yesterday. It had the latest update in it already. This is a really nice TV. If our house was bigger, I think I'd keep this one. Thanks for the help guys.

[tom66]

Re: Panasonic sc tnpa5081 rebuild

Get a bigger house or You Are Not Worthy of the Panasonic.

[johnboy1313]

Re: Panasonic sc tnpa5081 rebuild

...You Are Not Worthy of the Panasonic.

I'm really not

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

It's nice to fix these and make some bucks, but when something reasonably new with a bit of quality pops up, it's even nicer to treat yourself and keep it.

[johnboy1313]

Re: Panasonic sc tnpa5081 rebuild

The TV we currently have on the wall is newer but only 42". We have a blu-ray player that also has some internet apps. I think we'll be fine. I joke about wanting something bigger all the time, but in reality, I rarely watch TV anyway.

[tom66]

Re: Panasonic sc tnpa5081 rebuild

I've never found internet apps that useful... However, the picture quality of this generation Panasonic is superb. It was one of their first steps towards "reference" quality.

[bregva]

Re: Panasonic sc tnpa5081 rebuild

last board is troublesome. This was the prototype which was powered with shorted q701 q702.

Had 2 attempts and q661 fails on panel on. Anyway discovered P5V line in to gnd only had 360ohms.

Take a bit to find but one of the octal buffer iC marked C741 has failed and had 380ohm on its Vcc-gnd.(removed)

Also NEC opto PS9856-2-F3-AX is bad and no info on that one yet.

Hi everyone, I'm new here on the forum
I'm trying to repair the SC board, replaced all shorted components, but Q661 failed again on power up. I'm having hard time finding that C741 you mentioned, can you pin point it for me? It is on SC board right? I powered the set with buffers connected, but buffer boards seem fine, there are no shorts on them. Another thing, I did not change IC 501 as it seemed OK. I just changed another M81737fp as it had short between pins 7 and 8. Other than that I would not know how to determine if IC is bad. So maybe that another
M81737fp caused Q661 to go?
Thanks in advance

[tw2005]

Re: Panasonic sc tnpa5081 rebuild

Hi everyone, I'm new here on the forum
I'm trying to repair the SC board, replaced all shorted components, but Q661 failed again on power up. I'm having hard time finding that C741 you mentioned, can you pin point it for me? It is on SC board right? I powered the set with buffers connected, but buffer boards seem fine, there are no shorts on them. Another thing, I did not change IC 501 as it seemed OK. I just changed another M81737fp as it had short between pins 7 and 8. Other than that I would not know how to determine if IC is bad. So maybe that another
M81737fp caused Q661 to go?
Thanks in advance

Sorry to hear your repair failed. Did you repair it and then found this post or have you gone through my list of parts replaced and then had no joy?

One of the problems is that not all boards fail exactly the same and the jury is still out on my last board although i have found a number of items missed and I am chasing my tail a little because once the SC board stops shorting the VS the TV will apply power and new items are being damaged.

That's the same transistor giving me grief so you may be unlucky and have more difficult repair on your hands. I've still got parts in transit so I can have another crack at it, that way I feel this post will be more complete for what parts to check.

C541 is the marking on one of 2 octal buffers located left of the SC20 connector. IC561,562,563 all feed off the 5V in.

Can I suggest you list in a logical manner every item you found suspect, it's condition and what's been replaced and with what part#

Saying you replaced all shorted components is too broad a statement. I thought I had too but if that were the case it would be working.

Also any measurements/resistances taken and where.

I have good boards here to pick from so if you list any check points you want resistances or continuity checked for comparison , list them and I'll do my best to post that info.

I think the important thing here is to take your time working through the cct before powering up again.

The timezones don't help.

Post as many photos as you like especially anything that shows me enough detail of parts replaced, markings etc. Visually there was nothing obvious to to see fault wise but spotting a blown smd resistor that's 1mm I found hard, hopefully you have a magnifier too.

[tw2005]

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.