[Amps] 3CX800A gone South?

[Hardy Landskov]

I have a 3CX800A in an SB200 redone for 6 meters and turned it on for the first time in about a year. When I depressed the foot switch, the plate current went to 800 mA with no drive. So let up on the switch but I left the amp on trying to think what was happening.  About an hour later I pressed the footswitch again and the plate current was 70 mills which is normal. 
With 10 watts of drive I get 300 watts out but the plate current is 750 mA which is way too high. The tume cap will not dip the current either.
Any ideas what's going on? Oscillation?
73 Hardy N7RT