I've ran the 707 all day without shut down but the excessive heat can't be good, I wouldn't think. I'll probably set up some type of fan to run and put it on a switched outlet on the power center.

I don't think it's so much a worry about shutting down. Keeping any unit cooled will (should) prolong it's life. Remember when the office "computer" was in a big glassed-in room with a raised egg crate floor and always super a/c'd?

I dug up and old case fan and wired it up to an ac to dc 12v adapter. I'll see how well it works, I might need one that can move a bit more air.

That's what I did, Rick (TX-SR805). I found an old power supply that had a smallish plug (rather than a wall-wart) and just plugged it into the switched outlet on the back of the receiver. I have two fans running off that supply - one blowing down into one side of the unit and the other blowing across the top (it is in a semi-enclosed rack). Noise is not an issue.

My understanding is that a good part of the heat problem comes from the video processor, not the amplifier. That's why I have the fan blowing down into the right-rear of the unit (yours may have different architecture).

Both Peter and I have "vintage" Onkyo receivers also. I know mine runs warm. I also know it's been running almost non-stop for about 15 years.

I had an Onkyo 502 before this, it didn't run quite a hot as this newer unit does. I figured as you say Tom, it's the processor so I have it pulling the hot air up. The fan is located at the right rear.

I ended up replacing the fan I had with a 120mm fan. It is connect to the power center on a switched outlet. The bigger fan does quite a good job cooling the Onk.

Did you take any comparative temp readings after installing the fan, Rick?

Yes I did. The ir therm read 106°F after 4 hours of running at near reference levels. Before the fan was installed it was reading 128°F after heavy use.

Excellent! that's a huge difference.

Very impressive difference. How's the fan noise? Do you know offhand what brand of fan it is?