Panasonic TH-46PZ85U Power Issue

[sdinelli]

Re: Panasonic TH-46PZ85U Power Issue

This one ?
I have a board here from a 42" and it seems the values are different depending if its the MC301 or MC201.
MC201 is 101 (100ohms) MC301 is 201 (1kohm)

Nope, the one closest to the chip, by 3rd pin from top.
maybe its not even a resister? idk

Thanks tho

[diif]

Re: Panasonic TH-46PZ85U Power Issue

Nope, the one closest to the chip, by 3rd pin from top.
maybe its not even a resister? idk

Thanks tho

It's a tiny black square thing, think it's a small capacitor. It measures 87.52uf.

[sdinelli]

Re: Panasonic TH-46PZ85U Power Issue

hmm.. so anyone else have any ideas? i cant find the schematics just trouble shooting procedures.
what if i just leave it off?

[sdinelli]

Re: Panasonic TH-46PZ85U Power Issue

took the reading from the resistor in the same spot on mc301. its 4.7kohm
i compared all the other resistors and they have the same values.

[sdinelli]

Re: Panasonic TH-46PZ85U Power Issue

replaced resistor and put the new chip on. shes working great. got this for free and spent 10$ to fix. love it

[smartjohn]

Re: Panasonic TH-46PZ85U Power Issue

So for this fix, I have definitely decided that LESS is MORE !! I have a TH-42PZ80u with 10 blinks. Tried the freeze test on MC201 and the set came on perfect! Should have listed to Tom and the others and probably only done the CAP replacement. But, no I tried both replacing the Cap and IC on both boards. Now still seeing the 10 blinks. Pulled them both and did find one resistor was shorted with a solder flake but a re-test got me the same result. No other parts are missing so I am stumped, not sure where to turn.

Is there any way to test the entire SMPS OUT of SET with jumpers and light bulb loads to simplify the trouble shooting process? Thanks for any help!

[vinceroger69]

Re: Panasonic TH-46PZ85U Power Issue

The resitor that was shorted by accident may of now blown other parts its just finding where now, ive only done 1 of these sets and just replaced the two capacitors (what capacitors did you use) i used normal electrolytic capacitors so had to get the polarity right. Maybe one of your new chips or capacitors are bad? as you removed both boards to replace parts did you put them back in the right position? as i dont think these boards are the same.

[smartjohn]

Re: Panasonic TH-46PZ85U Power Issue

Hi Vince. These are all good points. At first used the round metal SMD electrolytic caps like norcal715 used in the video, with minus toward the top of the board. I next tried a yellow tantalum like i saw in some of the shots here, thinking I may have a bad new cap. I did mark each board (201/301), I am really a details type guy so this is why i am really frustrated. The 10k resistor that was shorted could have blown that IC.....! I still have one good IC that was pulled and I could try it back on that board...

[vinceroger69]

Re: Panasonic TH-46PZ85U Power Issue

I used norcals video too and marked both my boards too just in case and yes you have the capacitors on rite minus to top my guess its something on the board you shorted but what? yes change the ic if you have it spare it will rule it out. just be carefull as you keep removing the boards/parts, as the traces can lift off the pcb.

[smartjohn]

Re: Panasonic TH-46PZ85U Power Issue

So after further review, I discovered F301 was blown, which means 1 or both of the 16n55g mosfets in the circuit are bad. I assume this happened when I had replaced the MC301 board with the shorted 10K resistor. An eBay seller, best4less303, who offers a repair service for MC201/301, tipped me off to check both F201 & F301. I am assuming that F301 feeds MC301. So off to eBay to buy new mosfets!

[Alastair E]

Re: Panasonic TH-46PZ85U Power Issue

May well need the TEA chip too--if the MOSFETS have shorted.
Quite possible for them to have spiked and killed it...

[vinceroger69]

Re: Panasonic TH-46PZ85U Power Issue

So after further review, I discovered F301 was blown, which means 1 or both of the 16n55g mosfets in the circuit are bad. I assume this happened when I had replaced the MC301 board with the shorted 10K resistor. An eBay seller, best4less303, who offers a repair service for MC201/301, tipped me off to check both F201 & F301. I am assuming that F301 feeds MC301. So off to eBay to buy new mosfets!

It was nice of the ebay repair shop to give you that information for free a lot of places wont offer free advice/help so good on them.

[smartjohn]

Re: Panasonic TH-46PZ85U Power Issue

I absolutely agree! I was very happy that he helped me on the diagnosis. In fact I was looking on eBay for a source that carried the 16n55g mosfets (could not find them at DigiKey) and I found that he sold them at a reasonable price with US shipping. He was not even pushing me to buy his own. If I had found his listing in advance, I may have saved myself all the grief and had him do the chip swap and new caps. His total fee is about $40 US. Unfortunately, he does not do international. Maybe one of you chaps could start something similar on the other side of the pond! Not sure of the volume of demand though :>

[vinceroger69]

Re: Panasonic TH-46PZ85U Power Issue

His ebay shop prices seem very fair too be honest,i also wish i could find some more panasonics with this fault too fix but not many listed in the uk at the moment.

[smartjohn]

Re: Panasonic TH-46PZ85U Power Issue

So just a follow-up to close the loop. The problem was definitely MC201/301. I replaced the 301 section mosfets and was still getting 10 blinks. I decided to take the eBay guy (best4less303) up on his offer to re-do my boards with no guarantee that he could restore them after my attempt. Fortunately, he did an awesome job and had them back to me pronto. I stuck them back in and Bingo! She is up and running like new. Morale of this story, if you don't have the steady hand at soldering you used to 20 years ago, let someone else do it for $34.00 !! Also, he strongly recommends the metal caps. (I had used the orange mylar drops) Many thanks to best4less303 and I highly recommend his services if you need MC201/301 repairs.