blew something up on the marantz

I believe that I've just damaged my Marantz 2220B receiver. First, I have the speakers on the "remote" speaker terminals, as I was planning on later adding the Polks to the "Main" speaker terminals.

Okay, here's what happened... I've been listening to music all morning, actually getting a chance to get this receiver cranked up to where it can really shine. The receiver had been performing admirably, hardly even breaking a sweat. No distortion, no dimming of the front panel.... nothing. I had just gotten done listening to one artist, and was searching around for something else. When I started the next song, it happened to be a bit louder than the previous artist. Not amp-fryingly loud, by any means, but louder nonetheless.

Suddenly, my right channel goes quiet and all staticy and stuff. There's still sound, but it's much quieter and has a lot of static interlaced. I turned the receiver off for an hour while I did some chores, then came back and the same thing was still happening. Here's the weird part.... I pushed the mono button on the receiver, and the channel came back to life. I was thinking this was very strange, so I checked the headphones... they are not effected at all. So I put the speakers on the "main" terminals, and they play fine in both stereo and mono! So the only terminals that are effected are the remote ones, and they're only when it's in stereo mode. What did I do to this poor amp?

I hope it's nothing permanent. I saw no smoke, and there's no smell like burning electronics. And like I said, the thing barely even warms up, even after an hour or two of use. I know that it has two internal fuses, but you'd think that if one of those went, it wouldn't have sound at all, right?

Thanks in advance,

nadams