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[Amps] Triode metering circuitry

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Subject: [Amps] Triode metering circuitry
From: Byron Tatum <>
Date: Thu, 6 Jan 2022 02:19:04 +0000 (UTC)
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Hello-   Possibly someone can shed some light on this for me. Previous years I 
built the K1AGB 144 Mhz 8877 stripline amplifier. I duplicated the QST article 
very closely and used the exact same metering and bias circuitry. The amplifier 
works really great with no complaints and is reliable. However, when the 
amplifier is keyed it always shows 7 mA of "resting" grid current, without any 
drive whatsoever. The idling cathode current is 110 mA. I used the amplifier to 
test quite a few 8877 type tubes over the years and this 7 mA. of grid current 
showed up every time no matter which tube. I cannot recall if I keyed the 
amplifier without a tube to check grid current though.    I am curious about 
how the metering resistor string, as shown on schematic of K1AGB amplifier, for 
the HV returns to chassis ground instead of the B minus. Whenever you float the 
B minus above chassis ground if you return anything (such as metering resistor 
string) to chassis ground will it show up as "grid current" due to grid 
metering scheme? I had two resistors going from B minus to chassis, the second 
one was for safety. I used double the resistance on each of them as compared to 
the single resistor shown, so that I had the same resistance total.Thanks,Byron 
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