smoke from a pre-amp. why?

The other day smoke started coming out of my rc-995 pre amp. Then it died. Needless to say, it's on its way back to Rotel, but I wondered if anyone had any theories or opinions on why this could have happened. I had nothing unusual plugged into it, volume was normal, the unit was on top of a cd player on a shelf with open sides and back and about 1 1/2 inches clearance before the next shelf above.
It doesn't mean it overheated. Some component failed (capacitor, resister, etc) would be my guess. Maybe an electronics engineer will see the question and have a better answer. Good Luck getting it fixed
Capacitor failure. Juice comes out of the capacitor, spills on something hot and SMOKE. Once the cap is dead, the product usually stops working.
Capacitors can fail any old time. Usually they last a long, long time... but sometimes, just POOF!
From my practice(no theories for now) this could be much more than just a capacitor to go POOFfff but could also set some wires with no exempt to power transformer(depending on circuit protection), PC leads(that could be a tough fix depending on their density and thickness and finally PC-board itself(now that could only be cured if it's not burned to deep or through since the burned area is conducting!).
Building an amplifier is a tough task but building a reliable amplifier is even more tougher. The higher power the amp the higher collector voltages are applied and the tougher to build the amp.
Preamplifier amplifies voltage and most-likely have a low collector voltages as well as relatively low capacitance PS caps. It's possible for the manufacturer to accidentally reverse a polarity of one of the PS electrolytic caps that may cause different failures for example increased voltage drops accross resistors of various applications mainly power-drop or offset ones that will certainly be working in higher than normal temperatures.

BTW do you still have a warranty?
Or maybe it was to let you know that the coals were not quite ready for the BBQ?!
Lovely smell isn't it? I am sure is was nothing you did it just was probably weak from the get-go.
All electronical gear runs on smoke. Once the smoke comes out - they quit working. ~ George W. Bush

I hope it was under warranty. If it is out of warranty, I hope the repair isn't to costly. Good Luck to you on this.
Well....i think it broke.
sounds to me like your preamp had just finished having sex. . . .