[HAM] 22H problem

[mike p]

 when I start up any organ it's hooked to and play for approx. 5 min, the 
leslie starts to distort quite terribly and at the same time the signal 
diminishes until it goes away altogether. Any thoughts on what could be the 
trouble? Thanks - Al

Al,  Does the 6550 tubes glow orange after this 5 minutes of playing ?