i fixed a ton of these when i worked for sony. should be a shorted power amp IC. likely rear amp. but you need some experience here. best to take it to an authorized dealer...........luck. I working as electronic technician for service, but not audio service. My friends asked me to check their Sony HCD551. No sound from speakers. Looks like you siad amp gone. I can hear very very low sound. I red it can be some raley in subwoofer wich controling all speakers switching ON. If it is an amp, where it is? Where i can get schematics? Thanks for help, Alex.