Bad connection to battery, amp starving for current, power supply FETs shorted out from overheating... Now when you hook it up it is pretty much a dead short or almost that could be why you are getting such low voltage at the amp, without blowing the fuses... If you got 4.47 volts, it likely hadn't blown the fuses yet, if you went back later and got .56 volts, you got blown fuses... We can repair it, however it may not be worth it... What model was it again?