Please help me fix my beloved Panasonic TC-P65ST30

[Th3_uN1Qu3]

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

The value of that capacitor isn't critical. I would check the startup resistor of the power supply controller.

[Ren01]

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?

There is a ceramic resistor beside the blown capacitor around 0.32 ohms. It seems to still be good, but my multimeter is not accurate enough to say for sure.

I had to guess the blown capacitors value by comparing the size of what was left with the rest of the capacitors on the board. Not very scientific haha.

[Ren01]

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

The value of that capacitor isn't critical. I would check the startup resistor of the power supply controller.

Which capacitor value isn't critical? C404 or c411, thank you!

[Ren01]

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

Looking closer at the pcb, I think c411 is in parallel with the ceramic resistor Davi.P mentioned. That would explain the short right?

[Ren01]

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

Would it be stupid to place some Arctic MX-4 thermal grease (non conductive) between the mosfet and the heatsink?

Sorry, I have so many questions!

[Davi.p]

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

It is not that resistor, it must be non flammable round type, and burnt... it must be connected to source pn, follow it... thermal grease is a must..

[Ren01]

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

It is not that resistor, it must be non flammable round type, and burnt... it must be connected to source pn, follow it... thermal grease is a must..

Thank you! The mosfet originally had no thermal grease or thermal pad, I wonder if that's what caused the failure...

Anyways, the round resistors on the top of the board, (didn't check the surface mount on the bottom) seem to measure fine.

I guess all I can do is wait for the new mosfet to arrive in 2-3 weeks. Thank you again for all the help! I'll report back if the repair is successful or not then.

[Davi.p]

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

I don't advice to you to sleep quietly waiting, check the datasheet for the typical application circuit, if connected to the source pin there's a small value resistor to ground, then you surely have to change that resistor...

[Ren01]

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

I don't advice to you to sleep quietly waiting, check the datasheet for the typical application circuit, if connected to the source pin there's a small value resistor to ground, then you surely have to change that resistor...

I think I found the resistor you mentioned, but previously you said it wasn't it? Can you please confirm. I've attached the following:

1) The data sheet example circuit showing there must be a resistor attached source, R2
2) The example value of R2
3) A picture of the ceramic capacitor that I think is R2 (can't measure it well resistance too low)
4) A picture of the opposite side of R2 facing the side where the ceramic capacitor blew up showing a slight black mark.
5) the back of the of the PCB showing that Source and ground are both attached to each other via this resistor in parallel with the capacitor C411.

Sorry for all that. Are you saying I should replace this ceramic resistor?

[Davi.p]

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

Ok maybe that resistor is good, But with the shorted mosfet, where the circuit is open? if not it can catch fire..

[Ren01]

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

Ok maybe that resistor is good, But with the shorted mosfet, where the circuit is open? if not it can catch fire..

Definitely don't want a fire! What do you mean by shorted mosfet? When I removed the old mosfet, drain and source was shorted on it. Should I do more than replace the mosfet?

[Davi.p]

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

I mean, if mosfet is shorted then it flows too much current on the circuit, so something other must blow, in all the situations i've seen the critical one is the resistor that is made to break without burn, you don't even have a blown fuse, so where is the open? Without opening something must burn..

[Ren01]

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

I mean, if mosfet is shorted then it flows too much current on the circuit, so something other must blow, in all the situations i've seen the critical one is the resistor that is made to break without burn, you don't even have a blown fuse, so where is the open? Without opening something must burn..

The capacitor that blew up was between the source and drain. Could that be it?

[Davi.p]

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

No. But let's make things short, measure ohms between source pin and primary ground..

[Ren01]

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

No. But let's make things short, measure ohms between source pin and primary ground..

Source to ground resistance measures at 0.9 Ohms. My meter when touching the two probes together measures at 0.7 Ohms.

[Davi.p]

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

ok, strange thing but replace only the chip..

[Ren01]

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

ok, strange thing but replace only the chip..

Thank you!!!

[Ren01]

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

So, new mosfet from China arrived with new caps from digikey. Replacements parts were soldered in, but still no power at all

Maybe it's a fuse?

[Davi.p]

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

You told that fuses are ok... Measure D pin of I401, if 320 or 160v is present Replace R403 and check again I401 for short on D-S

[Ren01]

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

You told that fuses are ok... Measure D pin of I401, if 320 or 160v is present Replace R403 and check again I401 for short on D-S

Sorry it took so long to reply, life kept me busy. No short from drain to source and double checked all pins soldered correctly. Not sure I can check the voltage while plugged in with my cheap meter safely. Since drain pin is right above the heat sink, it would be easy to short. I could buy a replacement resistor on my next order instead.