[Amps] Drifting Power

[Pete Smith N4ZR]

FWIW, I see something very similar in my KPA-1500.  I had assumed it was 
software protecting the transistors, just in case.

73, Pete N4ZR
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On 10/16/2021 10:05 AM, Steve London wrote:
>   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
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