First check to make sure there isn't a loose speaker wire from one post touching another post which is the most common reason for the AVR to shut down. You also may want to try resetting the microprocessor (check Owner's manual) to see if that resolves the issue. If not, then pop the top and see if there are any blown fuses or any other wires that might be loose or disconnected. Otherwise, a repair shop may be able to help, but most likely you're looking at likely a $200-$300 repair bill, although the repair shop will likely give you an estimate for about $75, normally applied to the repair bill if it can be repaired.