Panasonic TH-50PX80U need help with a short!

[XmouseX]

Hey guys! I am working on a Panasonic TH-50PX80U. It keeps blowing fuses and will not power on. I have isolated the short at the SS board. I was going to just order a new board, but I wanted to see if I could possibly just fix it. My question is, does anyone know what usually shorts out on these boards? It only blows the fuse when I plug in the 15V plug to the SS board. I am pretty good at diagnosing problems, but I am not very good at finding shorts thanks!

[tw2005]

Re: Panasonic TH-50PX80U need help with a short!

What fuses blow?

If it's the 2 mains fuses on the PSU then check Q406 for shorted out if it's similar design to the tech sheet.

[XmouseX]

Re: Panasonic TH-50PX80U need help with a short!

I love you! Thank you tw2005! Where did you find this, I have been all over google looking for something on this. Thanks!

[tw2005]

Re: Panasonic TH-50PX80U need help with a short!

I love you! Thank you tw2005! Where did you find this, I have been all over google looking for something on this. Thanks!

So was this the problem?

[XmouseX]

Re: Panasonic TH-50PX80U need help with a short!

Yes, even though it my TV model was not listed in the fix, I replaced the transistor, both fuses and added in the film capacitor. Put it back together and it worked great! only took about 30 minutes

[tomwil]

Re: Panasonic TH-50PX80U need help with a short!

... added in the film capacitor ...

What are the specifications for Panasonic C426 ECQB1H103JZ ?? Or, what film capacitor did you use?

In one search, I found 50V 0.1U, but another search yielded 50V 0.01U. Which one, if any, is correct?

[tom66]

Re: Panasonic TH-50PX80U need help with a short!

The capacitor is "103" == 10pF x 10^3 = 10000pF = 10nF.

[tomwil]

Re: Panasonic TH-50PX80U need help with a short!

The capacitor is "103" == 10pF x 10^3 = 10000pF = 10nF.

Thanks, Tom. It appears that 10000pF is equal to 0.01uF, according to this chart, which would make the first document I linked to incorrect in its value.

Although I currently have no problem with my TH-42PX80U, should I add this capacitor as a preventative measure?

[tom66]

Re: Panasonic TH-50PX80U need help with a short!

I would recommend it after the repair but it's probably on there for later versions without this fault, probably in SMD format so you can't see it.
0.01uF = 10nF.

[pk7tanner]

Re: Panasonic TH-50PX80U need help with a short!

I love you! Thank you tw2005! Where did you find this, I have been all over google looking for something on this. Thanks!

/\ THIS /\

I picked-up a TH-42PX80U tonight for $25 and following the simple instructions laid out in the pdf tw2005 provided, I realized the previous owner had replaced the only one fuse. He had already replaced the mosfet, but when I looked at the board and realized he only replaced one of them, I checked the other and it was blown (he also gave me 7 new fuses). Replaced the fuse and it appears to work great. Is the mod in that diagram something I should still do then?

[tw2005]

Re: Panasonic TH-50PX80U need help with a short!

/\ THIS /\

I picked-up a TH-42PX80U tonight for $25 and following the simple instructions laid out in the pdf tw2005 provided, I realized the previous owner had replaced the only one fuse. He had already replaced the mosfet, but when I looked at the board and realized he only replaced one of them, I checked the other and it was blown (he also gave me 7 new fuses). Replaced the fuse and it appears to work great. Is the mod in that diagram something I should still do then?

If this is the first repair, that's about 5 or 6yrs out of it. How long will it still last for and how long are you keeping it??

Would not hurt too but I would'nt be too worried either way.

general purpose poly film 0.01uf 50VDC 5% tolerance

[pk7tanner]

Re: Panasonic TH-50PX80U need help with a short!

If this is the first repair, that's about 5 or 6yrs out of it. How long will it still last for and how long are you keeping it??

Would not hurt too but I would'nt be too worried either way.

general purpose poly film 0.01uf 50VDC 5% tolerance

I'm actually thinking of keeping it. It's incredibly clean and I believe the guy I got it from (even though it's from an ad I place on craigslist) when told me that he didn't watch a lot of tv. I've had really good luck with all things Panasonic (vacuum, power tools, air tools & my ancient microwave), and tom66 gives them a #1 ranking (he doesn't have any sponsorship deals that I'm aware of lol).
Should I be ok using it until I get the capacitor or what am I risking by not doing that mod? I still have to disassemble it to put thermal grease on the mosfet.

[tom66]

Re: Panasonic TH-50PX80U need help with a short!

These are fantastic tellies -- only 720p but still great for 99% of what everyone watches. Very well engineered, only the occasional rare issues.
Don't run it for long without thermal grease on the FET! It can overheat quickly without it.

[pk7tanner]

Re: Panasonic TH-50PX80U need help with a short!

These are fantastic tellies -- only 720p but still great for 99% of what everyone watches. Very well engineered, only the occasional rare issues.
Don't run it for long without thermal grease on the FET! It can overheat quickly without it.

That I'm doing right away. I fab'd a screw driver with a 90° angle, about 2cm from the tip, just to remove those lil buggers.
Why is it that Panasonic items have such long lives? Is it their engineering?

[tom66]

Re: Panasonic TH-50PX80U need help with a short!

I think it's part of Japan's ethos -- you see it with Toshiba, Sharp and Sony manufacturing too (as long as they're not rebadging.) After the 2nd world war, Japanese products were originally regarded as inferior to American products (sort of like Chinese products nowadays) -- but within around 20~30 years that had completely swapped around. And they haven't changed. The engineering is solid, well thought out, and products are well manufactured.

Back to the Future III has a brilliant line: Doc sneers and remarks, "No wonder this circuit failed; it says 'Made in Japan'." Marty replies, "What do you mean, Doc? All the best stuff is made in Japan." Shows the difference of about 30 years...

[tw2005]

Re: Panasonic TH-50PX80U need help with a short!

I'm actually thinking of keeping it. It's incredibly clean and I believe the guy I got it from (even though it's from an ad I place on craigslist) when told me that he didn't watch a lot of tv. I've had really good luck with all things Panasonic (vacuum, power tools, air tools & my ancient microwave), and tom66 gives them a #1 ranking (he doesn't have any sponsorship deals that I'm aware of lol).
Should I be ok using it until I get the capacitor or what am I risking by not doing that mod? I still have to disassemble it to put thermal grease on the mosfet.

You know you can access the run time within service mode if you really want know how many hours.

I've had 2 of that generation, one had 10 000 hrs and appeared to have no boards replaced. The PSU had not been touched.

[tom66]

Re: Panasonic TH-50PX80U need help with a short!

My 42" and 46" PZ80s have 7,000 and 4,000 hours respectively, both going strong. The only issue with the 42" was a cracked solder joint, the 46" had a loose LVDS connector. No major hardware issues really -- just minor production issues (catching the edge of the bell curve I guess.)

[pk7tanner]

Re: Panasonic TH-50PX80U need help with a short!

You know you can access the run time within service mode if you really want know how many hours.

I've had 2 of that generation, one had 10 000 hrs and appeared to have no boards replaced. The PSU had not been touched.

I did not know that. Would you mind telling me how or is pretty straight forward? I know I could look in the service manual, but it's easier to ask.

[tom66]

Re: Panasonic TH-50PX80U need help with a short!

Hold (-) on remote and press "0" three times on remote. After about 10 secs service menu pops up and the counter is on there, I believe.

[tw2005]

Re: Panasonic TH-50PX80U need help with a short!

Something like this. You have to activate the serv menu, then navigate to the field it is displayed in and then activate the timer count for it to display.