[Amps] Why does power output increase?

[Victor Rosenthal 4X6GP]

I did measure the voltage at the tube pins. I haven't measured it while 
transmitting, because the RF drives my meter crazy. I assume the voltage 
drops a bit. Unfortunately I no longer have my trusty analog voltmeter. 
I wish I did.

I'll measure the line voltage. But the only thing I can think of that 
would cause that to increase after long transmissions would be if the 
breaker on the line heated up and lost resistance. I have never heard of 
that!

73,
Victor, 4X6GP
Rehovot, Israel
CWops #5
Formerly K2VCO
https://www.qsl.net/k2vco/
On 05/06/2022 6:19, Jim W7RY wrote:
> *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*
> 
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