Why is my Krell fading out?

I have a pair of Krell FPB 350'S. When the music starts, one starts out fine, although with slightly less volume, but within 5 - 6 minutes the volume begins to fade and within 2 -3 minutes more there is no sound at all.

This sounds like a capacitor problem but perhaps one of you has had a similar experience or a solution.

I do not live in the U.S. so sending the amp back to Krell is not an option.