Electronics > Beginners
What is this device in a little 1970's bench power supply?
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jakeisprobably:
I took apart a little 12v power supply I picked up from a local thrift store. Inside it's very simple but I've never seen a device before like this little bulb in the pictures. It looks like a bimetallic strip based current limiter. It was in series with the output positive voltage terminal. What are these devices called, and why are they not used (much/if at all) today?
ciccio:
You are correct: it's a self resetting fuse.
Last time I've seen one I was much younger..

It is very similar to the bimetallic  fuses that are placed inside motor's windings.
An example: http://www.miottisrl.com/en/prodotto/sw1/
They are current and temperature sensitive (for motor or transformer protection).
The glass body make it less temperature sensitive, so it is in effect a simple current limiter.

Best regards
Towger:
I have also seen them used as a flasher, in ET (phone home) toys!
floobydust:
It's a self-resetting thermal circuit breaker.
They are kind of neat, they trip at say 5A and take almost a minute to reset (cool off).
strawberry:
old scool cristmass lights
contacts in vacuum can hold more current
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