Symphony Reset?

My Symphony has stopped working. It turns on, you can select the various modes ok, but all that ever comes out is something like radio static. The amp is working ok, CDs play (can swith tracks) - but no sound other than a wierd hiss.

So I've removed it, hoping that it would reset, I could re-enter the key and it might then work. But it never seems to want the key (after at least half-an-hour without ANY power.)

So is there any way to force this unit to completely reset? Does it contain any backup batteries like the CMOS on a PC?