The Amp/Tuner was working fine till I am ready to put it in the system. I push main power on and get a light at the switch but get nothing when the System power switch in pressed. The fuse inside (that I can see) is OK. I noticed oon the manuel that there is something they call the 'amplifier protection circuitry' could this have been 'activated and if yes can I re-set it somehow? I see nothing obvious inside. Appreciate any help.