I think you are over thinking this degassing issue? By adjusting the amount of bias diodes you can adjust the anode current.
On Monday, March 3, 2025 at 10:39:14 AM EST, Fran?ois via groups.io <18471@...> wrote:
So I went to full voltage tests with the 2 tubes in place. With zero bias I measure
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·???????? CW voltmeter 1700 V measures 236*8=1888 V intensity 175 mA; the tubes do not redden 298 W (2 tubes)
·???????? SSB voltmeter 2500 V measures 329*8=2632 V intensity 220 mA; the tubes redden 550 W (2 tubes)
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In low voltage tests 231 W (plate current 390 mA under 592 V) for one tube redden. The result therefore seems consistent.
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In my country (France) the power is limited to 500 W.
·???????? I could operate the L-7 on the CW position and by limiting the excitation 500 W RF output.
·???????? Periodically, run the amp in SSB position, without RF, with just the 220 mA quiescent current to make the tubes glow and thus maintain optimal degassing.
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I am concerned that by placing diodes in the cathode circuit to bias the grid slightly negatively, the quiescent current in SSB mode will not be sufficient
