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Assumed this was a spade terminal to earth and broke it off the power transformer. I think this is a ring lug thermistor? I get 120ohm across the two wires at room temp. Any idea what the nominal value might be? The markings E2 75, maybe 7.5kOhm?
Amp goes into protection mode without it so I've put a 2kOhm resistor in its place which lets it power on but the speakers are very quiet now. Could it be winding back the power in response to temperature? #hifi #electronics
@stardot think you're right about the purpose, attached to heatsink I assume?
It could be 75ohm positive temp coefficient (so that would be minimum value at stupid cold), so perhaps you need a 120ohm in there to restore normal function.. any idea where in the circuitry it connected in?
@phlash yeh that makes sense, most I see are NTC but an extreme cold reading shouldn't reduce power.. I'll try a lower value resistor and see what that does.
It's attach to the metal body of the transformer and leads back to the pre-amp (I think) so it makes sense if provides a feedback mechanism.
@stardot ah ok, power supply overheat protection, aka "too loud man!"
@phlash I have identified it as a muRata posistor but I haven't yet fully deciphered the part numbers. I think E2 means it senses 90C, it is probably a 100ohm@25C variant. Even so it is discontinued to I will have a time finding a replacement.
I have swapped my bypass resistor for 99ohms and this fixed the volume issue, even though I'm using mismatched 4ohm speakers from my surround system, it manages to get bass out of them and sounds great!
https://www.mouser.com/datasheet/2/281/bk-e1019i-e-1519151.pdf