What Is This Thing?

[industrialarts]

I found it inline with the AC on a MusicMan amp. I am guessing it's some kind of thermal overload device but I have no idea

 

[mjrippe]

Looks like a neon lamp.

 

[Walrus]

Resettable thermal trip?

 

[pucho812]

according to schematics I have seen it's called a thermal breaker

 

[abbey road d enfer]

Yes, although it shares many physical aspects with a neon lamp, I would vouch for a thermal resttable "fuse".

 

[industrialarts]

I had assumed it was thermal but how does it work? Does it break due to ambient temp or does a bi-metal strip heat up and break contact? Any ideas as to manufacturer or spec sheet?

 

[abbey road d enfer]

I had assumed it was thermal but how does it work? Does it break due to ambient temp or does a bi-metal strip heat up and break contact?

The latter.

Any ideas as to manufacturer or spec sheet?

Check "resettable thermal fuse".
https://fr.aliexpress.com/item/3280...xp_id=2c73abc2-3ce6-41ac-b4d8-658594dbee2d-14

 

[JohnRoberts]

That picture still looks like a neon lamp, if its a resettable thermal breaker probably bi-metallic.

Those other links look like PTC thermal fuses, that conduct again after they cool down.

JR

 

[abbey road d enfer]

Music Man documentation shows both a neon lamp (pilot light) and a thermal breaker.
Knowing the type of amp would help, because the pilot light is connected either across the 117V primary, with no external resistor (so must be a type with built-in resistor) or across the half-power HT secondary with an external resistor. Obviously it should be placed as to being visible from outside.

The thermal breaker should be placed very close to the power xfmr since it is supposed to detect abnormal heating, and connected in series with the primary..