Yeah, I don't know what else to suggest.
* Call Onkyo, tell them you just replaced 13 caps, and now your 876 is behaving erratically in regard to the rear's switched outlet (on all the time, doesn't switch anymore), and the receiver stays warm all the time now. Best to talk to one of their technicians.
=> My best guess: When you replaced all those 13 caps, somehow you did something to your 876 (a disconnection or some' like that) on the circuit board (PCB), with soldering one of the circuit traces or one of the wires, that have caused something awkward to the switched outlet.
If I was an electronic technician (I'm not, I'm an artist), I would ask you to show me the type of "custom work" you did here, say from some pics,
and then see if you touched or modified something that you shouldn't have.
But, life is fun, we all love to explore, fix things, and live happy with what we accomplished for the better, and also for the worst.
♦ You can probably find another 876 (second-hand) in excellent working order (classified adds from the right places) for only two hundred bucks.
If this is not an option, just buy a very inexpensive AC power cord extension with integrated switch (I have few of those myself @ home; five bucks each @ the hardware store).
Just situate the switch @ the best position in your room where you have easy access when watching movies and listening to music.
Do you know what I mean, or should I give you a link of such an extension "switched" AC power cord?