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Re: [Amps] Why does power output increase?

To: Amps reflector <>
Subject: Re: [Amps] Why does power output increase?
From: Victor Rosenthal 4X6GP <>
Date: Sat, 4 Jun 2022 16:43:23 +0300
List-post: <>
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.

Victor, 4X6GP
Rehovot, Israel
CWops #5
Formerly K2VCO
On 04/06/2022 16:26, 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.

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On Saturday, June 4, 2022, 8:23 AM, Shane Youhouse <> wrote:


    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
    < <>>

     > This isn't a problem, just a phenomenon that I would like to
     > 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
     > I'm interested in hearing theories about why this might occur.
     > --
     > 73,
     > Victor, 4X6GP
     > Rehovot, Israel
     > CWops #5
     > Formerly K2VCO
     > <>
     > _______________________________________________
     > Amps mailing list
     > <>

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