I'd start by ch3cking for voltage at the power plug on the amp board in the top box. It'll be the plug with the orange and black wires. If voltage is there, check all your plug connections back to all speakers and the motherboard in the bottom of the machine on the back wall. May turn out you have a bad MPU though. Last resort, turn the machine off and pull the MPU tray out, mounted to the side wall in the bottom of the machine and post a picture of it here on the site so we can look. You might be missing a chip or something