Replaced circuit breaker on IBM 1130 +6V power regulator

WEAKENED CB TRIPPING INCORRECTLY

As I had determined, with the machine drawing less than 9A from the +6V power regulator, the CB will trip off when power is turned on if it was warm. I power up the 1130, run for a while, then when I want to turn off power for a short time before turning it back on, the breaker will trip off. 

+6V power regulator

FIRST TRY AT ORDERING REPLACEMENT CB FOILED BY VENDOR ERROR

I bought a 25A CB that is close enough to the one included in the regulator. When the shipment from Amazon arrived, I discovered a problem. The plastic package listed the product as a 25A breaker, but then breaker inside was a 10A unit. I returned it to Amazon and waited again for the correct breaker to arrive.

Replacement breaker

MECHANICAL FIT IN THE REGULATOR

The failing circuit breaker provides three additional terminals which are used to indicate whether the breaker is turned on or off. The IBM 1130 does not make use of these, thus the replacement breaker didn't need that. I removed the wires for the indicator from the breaker and the regulator terminal block at the other end. 

The replacement breaker is nearly the same size, but differs in its width, thus the two mounting holes are too close together to have both attached with screws. 

Test fit

I was able to mount the new breaker  in the same location, using one screw. It seems well enough anchored. I wired it up and replaced the regulator in the 1130 system. 

Ready to re-install

Failing breaker

TESTING ABILITY TO CYCLE 1130 POWER WHEN IT HAS RUN FOR A WHILE

I brought up the system and did some work on it, letting the regulator warm up. I then flipped off machine power, waited 60 seconds, and turned the system back on. The power cycle worked exactly as it should. Annoyance resolved. It was occurring often enough that it would have been intolerable at its home when attempting to show off the working 1130 system.