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
W5FH
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