Beginner: any idea why R43 would have disintegrated?

[rthorntn]

Hi,

I have a subwoofer that powers on but doesn't work.

I've dismantled it and the amp (a rebadged Dayton SPA250) has the legs of a resistor at R43 but no body?

I found a diagram that's has it as a 10K connected between earth and the soft-limit circuit, I'm assuming a mains power surge but want to be sure before I replace it, I'm guessing it was a 1/6W or less as the body "gap" is tiny?

Thanks
Richard

[bostonman]

I may be wrong, but that looks like a thermistor since it has an oval circle around it.

[rthorntn]

Thanks, does a thermistor make sense, do they just explode then, would it cause the symptom I'm seeing, power on, no sound?

[bostonman]

I'm not exactly sure how the circuit works, but point A is connected to the left side near the J1 connector.

The circuit marked point A is also connected to standby and a temp node, so it's possible the circuit thinks the system is too hot and not turning on.

[rthorntn]

Thanks, I'm reading up on it now, they can explode and they do act as a sort of surge protection, I just had a good look at the soft-limit PCB and I don't see anything obviously wrong.  Probably just get a 10k thermistor and solder it in?

[bostonman]

Looking at the thermistor chart, it's 10k at 77 degrees F and the resistance decreases as temp increases.

Maybe stick a 10k resistor in the spot and see if it turns on.