Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Can someone please tell me what this part is?

The marking on it reads Toshiba and it measures approx 180 ohms.

I suspect it is a NTC resistor but would like confirmation.

Thanks!  :)

Clip an ohm meter to it, and heat it.  use a heat gun, or a hair dryer, or just hold your soldering iron right next to it for a minute.   Does it react?

otherwise it also resembles a "polyswitch", which is essentially a self-resetting electronic fuse.

I see a polyswitch in tweeter protector circuits in crossovers.  WHich bring up a point.

Whenever you want someone to identify a part, it REALLY helps to tell us what it is used in and what it connects to.  If it is wired in series with a mains connection, then I'd agree it probably is a thermistor.

Thanks Enzo.

Sorry, I should have mentioned this is in the power amp section of a circuit I am tracing.
Haven't finished the schematic yet... so I'm not sure where exactly it is in the circuit.

Its an old 60's or 70's SS Teisco amp.

I'll try the heat test and see what happens.

It´s very probably part of the power transistor biasing net.

Thanks JM,

Here's a partial schematic.
I'm not yet done repairing this amp, or finished with drawing layouts and schematics.

I'll do a full post on this amp in the schematics section later.

I did test this device by connecting my multi-meter on ohms and letting it sit there for a while....

It stabilized at 220 ohms.

I didn't have to break out the heat gun cuz just picking up the device,
the heat from my fingers caused the resistance to fall quite noticeably.

I assume that means it's an NTC resistor? Thermistor?

Therm 1 in the picture.

Thanks!  :)

Edit;
Oh.... and I assume TR1 100K is bias adjustment?
Any tips for setting this?
Thanks!