Please help me fix my beloved Panasonic TC-P65ST30

[Ren01]

My beloved TC-P65ST30 suddenly stopped turning on last week, no LED lights on at all, and it deserves a lot better than being tossed out. After some youtube troubleshooting steps, I was able to find a blown ceramic capacitor, C404 on the main power supply board, picture attached. All 5 fuses on the PSU seem to have continuity.



I’m not sure what the actual rating was since the label side is blown off, but there are other capacitors of similar size on the board rated at 470pf and 1KV. Would it be a safe bet to replace the cap with one rated with this?

I also check the adjacent capacitor, C403 and it seems to measure as a short. I guess I should replace that too?

My concern is that there might be bigger issue that is causing these capacitors to blow in the first place. Should I go ahead replace the capacitors and hope for the best? I’m not sure how to check if the inductors are good. Some are measuring low resistance and others are measuring as an open.

Also, I’m not sure, but these IC’s look kind of dodgy too. One might be a little malformed.

[ivtec]

Re: Please help me fix my beloved Panasonic TC-P65ST30

https://www.badcaps.net/forum/showthread.php?t=77174

https://www.youtube.com/watch?v=EShySnyZl1E&t=139s

[Ren01]

Re: Please help me fix my beloved Panasonic TC-P65ST30

https://www.badcaps.net/forum/showthread.php?t=77174

https://www.youtube.com/watch?v=EShySnyZl1E&t=139s

Thank you! Your second link in particular seems to have a similar failure. I replaced the cap on mine already and it still doesn't power on :/

[Davi.p]

Re: Please help me fix my beloved Panasonic TC-P65ST30

These photos are way too few to understand something of the board without a schematic... Don't use that method of posting picture, use paperclip in advanced editor, first to upload them, second to attach..

[Ren01]

Re: Please help me fix my beloved Panasonic TC-P65ST30

These photos are way too few to understand something of the board without a schematic... Don't use that method of posting picture, use paperclip in advanced editor, first to upload them, second to attach..

Thank you, I'll edit the first post. What additional photos would you recommend?

EDIT: Seems I can no longer edit the first post.

[Davi.p]

Re: Please help me fix my beloved Panasonic TC-P65ST30

Total and some zoom in..

[Ren01]

Re: Please help me fix my beloved Panasonic TC-P65ST30

Hopefully my updated last post will suffice. Please let me know if there are any other photos I can provide.

[Ren01]

Re: Please help me fix my beloved Panasonic TC-P65ST30

The circled red components are showing low resistance.
C403 ~3.5 Ohm. This has already been replaced, but short persists.
C411 ~1 Ohm
C408 ~100 Ohm

C404, the blown capacitor, has been replaced with a 470pf 1KV capacitor too.

[Davi.p]

Re: Please help me fix my beloved Panasonic TC-P65ST30

Now the goal is to show you where to test with a cellphone..
Do you know how to test diodes, mosfets and diode bridges and how to identify them? If yes start to test them, all the ones under heat sinks.. then test all varistors, them are two legs black round items, all in primary seems..
C404 is across high voltage and low voltage pins of the I401 that is a power oscillator for the transformer, its inside power mosfet is in short.. check if under heat sink there is a 2W resistor low ohm open...

[Ren01]

Re: Please help me fix my beloved Panasonic TC-P65ST30

Now the goal is to show you where to test with a cellphone..
Do you know how to test diodes, mosfets and diode bridges and how to identify them? If yes start to test them, all the ones under heat sinks.. then test all varistors, them are two legs black round items, all in primary seems..

Not super sure how to test those. I only have a basic multimeter, but I think diodes should be low resistance one direction and open the other way? Mosfets just shouldn't be shorted? Don't know what a diode bridge is haha.

[Ren01]

Re: Please help me fix my beloved Panasonic TC-P65ST30

C404 is across high voltage and low voltage pins of the I401 that is a power oscillator for the transformer, its inside power mosfet is in short.. check if under heat sink there is a 2W resistor low ohm open...

Will do!

[Davi.p]

Re: Please help me fix my beloved Panasonic TC-P65ST30

yes for the diodes/mosfets, diode bridges are groups of 4 power diodes integrated in a chip, you can find inside draw on the web, you have 4 of them, two in the slim ac input board and two to the secondary to left of two transformers. Test them so, there's a mark on board for the - and +, there are 4 pins, put black to - pin red to the near pin, must read open, shift both probes one pin to the right, read open, so on until red probe is on the +, now swap probes and restart from - pin, repeat the same but must read low ohms in ohm, low volts in diode mode..

[Ren01]

Re: Please help me fix my beloved Panasonic TC-P65ST30

yes for the diodes/mosfets, diode bridges are groups of 4 power diodes integrated in a chip, you can find inside draw on the web, you have 4 of them, two in the slim ac input board and two to the secondary to left of two transformers. Test them so, there's a mark on board for the - and +, there are 4 pins, put black to - pin red to the near pin, must read open, shift both probes one pin to the right, read open, so on until red probe is on the +, now swap probes and restart from - pin, repeat the same but must read low ohms in ohm, low volts in diode mode..

Thank you! There's no resistor under the heat sink, only one diode. Do you think I should go ahead and remove it and try to source a replacement?

[Ren01]

Re: Please help me fix my beloved Panasonic TC-P65ST30

Desoldered the mosfet and heatsink It went by surprisingly easy! No idea how to test it though lol. I'll try pulling up its data sheet.

[Davi.p]

Re: Please help me fix my beloved Panasonic TC-P65ST30

first dismount it, then measure between the leg connected to transformer and the one to negative if there is a short, swap also probes, if short or open then must replace it..

[Ren01]

Re: Please help me fix my beloved Panasonic TC-P65ST30

first dismount it, then measure between the leg connected to transformer and the one to negative if there is a short, swap also probes, if short or open then must replace it..

Do you mean the two pins circled in red? I think, but I'm not sure it's pin 1&2 or drain and source according to the data sheet?

When the two circled pins are checked for continuity I get 1 or 2 ohm regardless of which probe touches which lead, but it also seems to take some time, a few seconds, to reach that figure.

Edit: Oh, awesome! the short on the capacitor C403 disappeared after I removed the mosfet! It's now 125 ohm one way and open the other! Thank you so much! C411 is still shorted though, should I replace it too?

[Ren01]

Re: Please help me fix my beloved Panasonic TC-P65ST30

If I’m reading the datasheet for the str y6766 correctly and following pcb traces correctly c411 only connects source to ground. What would be an appropriate value to replace the shorted capacitor?

I think this is a bypass or decoupling capacitor?

[Ren01]

Re: Please help me fix my beloved Panasonic TC-P65ST30

Odd that the sample circuit off the mosfet data sheet doesn’t have a capacitor from source to ground. Do I even need to replace this surface mount cap?

[Ren01]

Re: Please help me fix my beloved Panasonic TC-P65ST30

This diagram from the data sheet has me second guessing c404’s capacitance which I guessed as 471pf and 1kv when it is 100pf 2kv in the diagram :/ someone in a previous YouTube comment said it was 330pf at 1kv

[Davi.p]

Re: Please help me fix my beloved Panasonic TC-P65ST30

Yes for the 1 & 2 pins, but since there is a source pin there is / are also a 2w less than 1 ohm resistor connected to source or many smd resistors in parallel (1/2 ohm). Why you have guessed 470pf?