I recieved a M100 in for service that goes into protect mode upon start up. checked all the audio outputs and driver sections. rebuilt the powersupply and charged the caps. someone recapped it un the past and pulled out all but 1 passthrus and was hoping after repairing the passthrus the amp would be stable.
If they re-capped it because the caps leaked (one of the few amps that actually need some recapping), the board could have electrolyte in the board that's causing electrical leakage. You're going to have to see where it's being driven into protection at the driver IC and follow it back.
I replaced the KA3525a and powered the amp with out the current limiter this time and both the yellow and red led were still on. After about 30 to 45 seconds I heard a small pop and electrical smell but could not isolate where it was coming from. After that the rails would not try and activate nor did it pull any current draw. This led to the conclusion that the amp may have powered up backwards and the lm393n ic was defective. I removed that ic and found that is was cracked on the bottom. After replacing the lm393n the amp powered correctly and bbn is now working properly.