well,i own an RM50HB head and i just had the "power" button break on me last weekend.i went to press it to turn on the amp,but found it locked up/seized in the "OFF" position.i pressed on it a little harder a few more times,then it broke free,but now just flops back & forth without actually powering on the amp...pretty upsetting seeing that i bought the head brand-new three months ago and,honestly,have not used it more than 12-15 times...i just dropped off the amp head to Randall early this morning since they're located about 35 minutes away from me.i'm concerned now at the build quality and/or parts quality...otherwise,i love the mts series concept & versatility.i just hope there will not be a slew of other problems to come in the near future.we'll see,i guess......