blowing breaker on the amp means fried main filter caps (the great big ones)
or
fried bridge rectifier.
rectifier is easy to test with a volt meter... pull all the connectors off, set meter to diode check. place black probe on the (+) terminal (it's marked) and test the 2 adjacent corners. each should read about 0.5ish. next put your red probe on the (-) terminal (it's kitty corner diagonal across from the (+) terminal and repeat the 2 adjacent terminals again. each should read 0.5ish if you real one that is zero (or full scale depending on your meter) it's shorted if you have one that reads open (or infinity scale again depending on the meter) it' open. shorted or open, both are bad and will need to be replaced. if all 4 internal diodes read 0.5, you have dead main filter caps. good luck finding them. they are super expensive for a compatible value....unicorm poo for original.
EDIT - my bad, the 60107438 amp has individual diodes attached to the caps and not an all in one rectifier module... check them all. if you find one bad, it might be orth it to swap them out for a modern module like a KBP5010 which will do up to 50a with 1000v peak.