[Amps] Why does power output increase?

[Jim W7RY]

*I'm curious Vic...*

*See below"*

On 6/4/2022 4:35 AM, Victor Rosenthal 4X6GP wrote:
> This isn't a problem, just a phenomenon that I would like to understand.
> I have a TL922. Mods include directly grounded grids. I also measured 
> the filament voltage with my Fluke true RMS meter and put a small 
> resistor in the primary of the filament transformer to provide exactly 
> 5.0v in standby.
*Where did you measure this voltage. Best is to wrap a small wire around 
the tube pins, (all 3 of them) and measure the voltage at each tube.*
>
> It has been running with the same genuine Eimac 3-500Zs in it for 
> about 6 years.
>
> So here is what happens: after a longish CW transmission, the power 
> output INCREASES. On 20m, for example, it may go from 1200 to 1400 
> watts. When it cools, the power drops back.
>
> I've noticed this with several wattmeters. I have observed no change 
> in SWR when this happens (it's 1:1 thanks to a Johnson KW Matchbox).
>
> It happens when the amp is driven with an Elecraft K3 and also a TS890s.
>
> I'm interested in hearing theories about why this might occur.

*I cant add anything about what your seeing... Other than is the line 
voltage changing?
*

*73, Jim W7RY*