I powered up my 5500 for the first time today and everything seemed fine, but after a few minutes it tripped the circuit breaker. I tried unplugging everything except the main connector and still had the problem, but it works fine if I use the secondary power connection on the expansion cable as long as I don't turn on the switch for the 5500. Also, when it blew the circuit breaker the first time, it also blew the fuse on the expansion power connection. Separately, I'm seeing very high and erratic CHTs which may or may not be related.