[Amps] HF amp output power dropping

[Tom Rauch]

I'm not sure how to respond to my first thread. Sorry if 
this is a duplicate.  I have been trying to find the cause 
of my amplifier's output power falling off. Last night I 
checked it by transmitting a 400 watt CW signal into dummy 
load. After 1 minute output dropped by about 50 watts. At 
higher wattages the loss is more pronounced, at 600 watts it 
may drop to 400 over a minute time. Now when I apply drive 
the filament voltage INCREASES. It always used to decrease 
under load.  That might be a clue, I don't know.
Thanks for all the help on this.>>

Jordon,

Maybe I'm missing something. I don't see anywhere what type 
of amplifier you have.

Without knowing the type and a little more about it, any 
answer could only be a very wild guess.

73 Tom