[Amps] Drifting Power

[Steve Thompson]

Inductor in the output side warming up slightly and shifting value as
it changes size? Is the output tuning sharp?

Can you tweak the output tune/load so it gives full output immediately
(and then maybe drifts downwards)?

Steve G8GSQ

>  I have a Commander HF-2500 Magnum, with a pair of 3CPX800's. Great amp.
> 
> It has one quirk, and only on 15 meters. If the amp has been dormant for a
> while, the output power is initially low: about 1100 watts. Key down it
> gradually rises up to 1500 watts over about 10 seconds. After that, if I
> intermittently transmit, at least every 5 minutes, it will stay at 1500
> watts. Only after being idle for ~30 minutes will it go back to the low
> output state.
> 
> My thought is that something in the input pi network is heating up.
> However, I have accurate SWR/power meters on both the amp input and amp
> output. Neither the input power nor SWR is changing as the output power
> rises. As the power rises, the grid current drops, but the plate current is
> unchanged. Again, this is only on 15 meters.
> 
> Suggestions ?
> 73,
> Steve, N2IC