Replace the power fuse for the Onkyo TX800 receiver.
Remove the two screws on both sides of the receiver. Keep these and the rest of the screws in a safe place.
Remove the top screw on the back panel.
Slide off the case to expose the internal components of the receiver.
Locate the fuse.
Gently wedge a small screwdriver in between one side of the fuse and the contact.
Remove the fuse with your thumb and forefinger.
Examine the fuse. If the wire within it is broken, you will need to replace it with a new, 125 Volt, 4 Amp fuse.