Yamaha HTR 5440 Won't Turn Back On

I was playing music through my Yamaha HTR-5440 at approximately half volume for 3-4 hours. I had 7 speakers connected and they were all running for most of the time. After this time, the music simply stopped and the receiver wouldn't turn back on. When I tried to turn it on, it would simply go "click" like it usually did when I turned it on, the screen remained blank and then "click" again as it turns itself back off. I noticed it was warm so I left it until the next day but it still didn't want to turn back on. The fuses on the board seemed to be fine and my local audio shop checked the capacitors, they're also fine. I'd feel confident that I'd be able to fix this thing, I'll put the time in but I just want to understand how it works and what the root of the problem might be.