[Amps] Why does power output increase?

[Victor Rosenthal 4X6GP]

The power increases after I transmit for a while. Then if I leave the 
amp on standby, it goes back to what it was before. But this resistor 
has the same current through it whenever the amp is on. If it were 
dropping in value, it wouldn't matter whether I was transmitting or not. 
The power would go up and stay up. So I don't think this is the problem.

73,
Victor, 4X6GP
Rehovot, Israel
CWops #5
Formerly K2VCO
https://www.qsl.net/k2vco/
On 04/06/2022 16:26, gudguyham at aol.com wrote:
> I agree with Shane and was exactly my thought, however resistors usually 
> go up in value when they get hot.  I would get rid if that resistor 
> faster than you can say Rumpelstiltskin.
> 
> 
> Sent from the all new AOL app for iOS 
> <https://apps.apple.com/us/app/aol-news-email-weather-video/id646100661>
> 
> On Saturday, June 4, 2022, 8:23 AM, Shane Youhouse <kd6vxi at gmail.com> wrote:
> 
>     Vic,
> 
>     1.  You want 5.0 volts under full bore TX, not at receive.
> 
>     2.  I'd suspect the filament primary resistor.  If it's heating up and
>     dropping resistance, more current will be allowed through.  This
>     will cause
>     the voltage on the filaments to rise su sequently increasing
>     emissions from
>     the tubes.
> 
>     Is the resistor in the airflow to keep it cool?
> 
>     --WP2ASS / ex KD6VXI
> 
>     On Saturday, June 4, 2022, Victor Rosenthal 4X6GP
>     <k2vco.vic at gmail.com <mailto:k2vco.vic at gmail.com>>
>     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.
>      >
>      > 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.
>      > --
>      > 73,
>      > Victor, 4X6GP
>      > Rehovot, Israel
>      > CWops #5
>      > Formerly K2VCO
>      > https://www.qsl.net/k2vco/ <https://www.qsl.net/k2vco/>
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