This is blown power supply FETs or rectifier. There might be more damage to the amp than that single component. Is it drawing a lot of current or what?
Half-*** previous repair job to begin with. All FET's which are parallel with blown ones should be replaced, they need to have very close specs for good reliability. If I see correctly on pics amp uses RFP50N06 FET's - they are cheap...
Mouser and Digikey has better prices on these. Trust me, amp will never be reliable if you replace just blown ones. All parallel MOSFET's should be replaced.