Have you checked the fuse?
From Bose Troubleshooting guide:[br]
”AC mains power is connected by the line cord via jack J1. A slow acting fuse F1 is connected between J1 [D7] and the locking primary connector J3 (or J2 or J4) to protect against faults. A Metal Oxide Varistor (MOV) VR1 is placed after the fuse and across the line. It is used to protect against lightning strikes and other line transients. “
I did some research and it sounds like bad solder joints are common in this unit, So I would look for any cracked joints, cold solder, etc. while you are in there inspecting the fuse.