I have a fairly new DRRI that I use as a pedal platform. I play 99% of the time through the normal input side of the amp, but the other day I plugged into the tremolo/reverb side and the amp began to squeal immediately. I'm guessing its a bad tube somewhere in the circuit. Any help on how to trouble shoot would be appreciated. Amp is probably still under warranty but if its an easy fix I'll just do it myself. Thanks.