Panasonic TC-P60S30 - no standby voltage

[BobbyMJ]

Hi All,
Wanting to learn some electronics repair skills.
I found a non working Panasonic TC-P60S30 and this is my first project / attempt.

So far I have found a blown cap on the main power supply board.
After replacing it there's still no standby power.

Poked around and found a resistor on the PSUB power supply board that measures open.

An online resistor calculator shows this is a 93k ohm resister.

My questions:

Is that correct, 93k ohms?
Is it a fusible resistor?
Lastly, how do I know what wattage?

Thanks

[lotas]

This is a megaohm resistor. It doesn't play any role in turning on.

[BobbyMJ]

This is a megaohm resistor. It doesn't play any role in turning on.

Thanks, that makes sense.

Testing with the AC plugged in I found the following:

F103
D102
D401
R104
D402
J33

All the above have over 120V

The capacitor to the left of C501 has voltage, the other large capacitors have little to nothing.

J38 only has 2 volts as does many things after that.

Could L401 be the potential culprit?
What kind of resistor is that?

Thanks

[lotas]

L401 is not a resistor (the resistor has the designation Rxxx on the board), but an inductor, choke, coil (they have the designation Lxxx).

[BobbyMJ]

L401 is not a resistor (the resistor has the designation Rxxx on the board), but an inductor, choke, coil (they have the designation Lxxx).

Thanks again lotas !

While following where the power goes on the back of the board, came across this resistor that measures open.
Assuming that shouldn't be the case?

Wasn't able to find that exact one through Digi key or Mouser that's in stock.
Know of an equivalent resistor or an alternative way to go?

[BobbyMJ]

Can the above resistor be replaced with a metal film resistor with the same specs?
Like this one: https://www.be-electronics.com/product_p/2wd56.htm

[lotas]

This is a ceramic, two-watt, current resistor and acts as a fuse, it does not just burn out, look for a short or low circuit in the circuit after it, these can be diodes, PWM microcircuits, MOSFET transistors...

[BobbyMJ]

Have tested almost everything including removing almost all of the mosfets to test out of circuit and so far, can't find anything else.

Replaced the circled ceramic cap (image below) which is in the circuit after the resistor, it was blown / cracked open.

Do you think a blown cap like that can be a symptom or the cause?
Can a ceramic cap short on it's own?

[lotas]

Yes, maybe they often explode, have cracks and short circuit, if you change it, then with a higher voltage of 2-3 kV.

When they are shorted, they often take away the MOSFETs (and the PWM, with a built-in MOSFET, like yours) sometimes it passes, and all you have to do is change the ceramic capacitor (resistor, fuse).

[BobbyMJ]

Yes, maybe they often explode, have cracks and short circuit, if you change it, then with a higher voltage of 2-3 kV.

When they are shorted, they often take away the MOSFETs (and the PWM, with a built-in MOSFET, like yours) sometimes it passes, and all you have to do is change the ceramic capacitor (resistor, fuse).

You're spot on.
Guess I didn't remove that mosfet above the circled ceramic cap to test.
Did that last night and it is indeed shorted!

Ordered the mosfet and will try to find a higher rated ceramic cap.

Need to order a new ceramic resistor but am unable to find the exact one.
Here's the specs ( https://www.koaspeer.com/pdfs/BPR.pdf ):

BPR26 -- 2w .56 ohm 5%

The BPR26 is proving to be difficult to find.

Can I substitute for something like a BPR56 (https://www.mouser.ca/ProductDetail/...9wU3nkyw%3D%3D) ?
has a higher wattage though ( 5W) , would it be correct to say bad idea, almost like putting in a large rated fuse?

Or substitute with a metal film resistor with the same specs as the BPR26?


Thanks again for your help and pointing me in the right directions.

[lotas]

Well, if the MOSFET is shorted, check its wiring (driver, low-resistance resistors, diodes, zener diodes,...), and you can replace the 2 W resistor with a metal film one.

[BobbyMJ]

Well, if the MOSFET is shorted, check its wiring (driver, low-resistance resistors, diodes, zener diodes,...), and you can replace the 2 W resistor with a metal film one.

Will do, thank you