GE M935AWL restoration

[Yamamaya42]

Originally Posted by bandersen

I was able to get the circuit breaker working with some deoxit. I also have a few used but good breakers.

I'm not sure how the rating works for these.
This set pulls about 3 amps, but I see a lot of breakers label "hold 2.1A". What exactly does that mean? Seems like they are undersized?

It is a bit confusing, from what I understand, they are all slow acting, there is the sustained “hold at” rating, and the trip at rating, but it is never clear what the trip rating is, or how long it must be at or over that threshold for it to trip.

I remember dissecting a bad one a long time ago when I was in High School to see how it worked, it has a bimetal contact that's reset by the button, and wrapped around that is a heater wire that has the current running through it.
And, yes, the contacts do burn and fail often.

[Yamamaya42]

this is WAY too big, gotta wonder what it's for, but it is the only one i see with both ratings on it, hold and trip.

https://www.ebay.com/itm/30326748117...Bk9SR8D54sq7ZA

[Yamamaya42]

I also got one of these to fix the burned focus connector.
https://www.ebay.com/itm/225235664833

[bandersen]

Thanks for the links. Just realized I'm being stupid. The breaker is not whole the whole set - it's only for the B+ supply! The filament supply is fused separately. The common 2.1 amp hold type is probably fine.

[Yamamaya42]

There is one way to see how much the draw is, including surge, if the breaker is holding, just AC amp measure with peaking across the faulty / removed thermistor, that should give some idea what kind of breaker hold/trip will work.

[Yamamaya42]

FOUND ONE!

but it's with 2 lesser ones.

https://www.ebay.com/itm/315321107869

tip point 3.25 amps.

[bandersen]

I have the chassis pulled. Can't power anything without putting it all back together. Sames does list it as a 3.1 amp breaker.

[Yamamaya42]

Originally Posted by bandersen

I have the chassis pulled. Can't power anything without putting it all back together. Sames does list it as a 3.1 amp breaker.

that's the only listing for a LITTELFUSE CIRCUIT BREAKER 8153.25, which Sames lists as a replacement I can find.
So I guess it's hold at 3a or so which seems high to me and trip at 3.25 amps.

Get it while you can!

[bandersen]

Parts have been ordered. Meanwhile spot checked a bunch of resistors and caps. All are well within spec. Well, except that 0.047 across the AC line. It's very leaky and in the trash.

[bandersen]

I measure about 120 ohms cold on the damaged thermistor. That got me thinking a CL-90 might be a good replacement. It can handle 2A and is 120 cold and about 4 ohms hot.

What do you guys think?

[Yamamaya42]

Originally Posted by bandersen

I measure about 120 ohms cold on the damaged thermistor. That got me thinking a CL-90 might be a good replacement. It can handle 2A and is 120 cold and about 4 ohms hot.

What do you guys think?

It should work. You can always try and see, with the vintage combos sold, they always show the cold rating, but rarely the hot.

[bandersen]

Does anyone know the significance of white tipped tubes?

[Yamamaya42]

I have seen that a few times before, not sure why it's done. :O

[Electronic M]

I've seen red and yellow tipped tubes before too...No clue what it means.

[John Adams]

See if they look like original tubes. Manufacturers could mark them to identify them if they were part of a warranty claim. Just a thought.