Receiver shuts off on its own

I have the same receiver and the way to fix is simple. in the main board of this unit there are 5 connectors and they slide into other components like Lego. the issue is the king of material they are made of it's cheap. if you reseat the mainboard it will fix it for a day or two, them it will start again. the easyway is to re seat the board and put a fan inside of the receiver between the transformer and the inside of the amp pointing down about 20 degrees connect the fan to a ajustible voltage adapter and connect it to the outlet in the back of the unit. so it comes on when you turn it on. this voltage adapter is cheap. the adapters people buy for phones and or MP3's at Radio shack or Best buy it goes from 1.5v to 12 volts/ this way you can control how loud the fan is in side the receiver. i find 4.5V does the trick. The connectors on this board start to loose contact with some of the pins when heated. the fan keeps it cool enouth to fix the issue. I fixed manny these ONKYO 804's this will fix it. you just have to do it. the main board is inder the HDMI board in a Vertical position running from one side to almost the Power supply. it has 2 screws also holding it in the inside middle back of the amp. Becarefull with these amps 75 V at 23amp's DC is no joje leave it off for a couple of hours to satart working on it. Good luck.

Yeah, it's clearly either overheating or shorting out and turning itself off before it gets damaged. It'd first make sure it's cool enough since these unit pump out a LOT of heat and then check speaker cables.

I had this same problem it turned out my subwoffer speaker wire got unplugged!

Also check ventilation of the unit, it could be a self protect too due to a heat related issue....

Take it to a repair center because your audio ICs amplifiers are damaged.Good luck.