Well, it looks like I've been barking up the wrong tree. This is obviously a power issue. I hooked up an old Infinity Primus center speaker that I still had. When I turn on the 7700 I get bad noise (which seems to be lasting longer each time now)......and that old familiar burning smell started coming from the center. It's not blown (yet), but now I'm thinking that I've overloaded the AC circuit, and the damage is cumulative every time I power up the preamp/amp.

So (here's my ignorance showing again) do I need some sort of power conditioning......or a dedicated 20-amp circuit? Or something else. Right now I have everything shut down and am afraid that I'll do more damage if I keep powering up.