Glenn,

Intermittent problems are nearly impossible to diagnose, especially without seeing your rig first hand. Unfortunately, I don't have time to drive to Ohio to help you out right now, but if and when I get a week off, it may be on the adjenda. In the mean time, the best advivce I have is to try to duplicate the same conditions again, using the exact same cables, etc. Fading audio is usually a very bad sign of an amp heading south, and the culprit is frequently the amp's internal power supply.

Question: Is your mic fired through your keyboard, and if so, does the board have internal speakers so it could be monitored separately from the rest of the system?

If you're firing everything through a mixer, mic and keyboard separately, then that would be the logical place to look.

Like I said, kinda' hard to diagnose with so little information and not being able to see the rig up close and personal.

Good Luck,

Gary