David's Denon AV receiver turns on/off randomly. What's going on? Leo says that all home theater gear are computers now, and as such, they are all solid-state. As such, they're not very fixable. But it could be an intermittent power spike that is causing the AVR to turn on/off. A power conditioner could fix it by providing a steady supply of power without interruption. That's the one solution that David can try. Absent that, it's probably cheaper to buy a new AVR rather than try and repair it. Power conditioners include Trip Lite, APCC.
Note, power conditioners aren't surge protectors.