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Worthy of mention is the multifunction meter switch, and the methods used to meter screen, grid and plate current, as well as plate voltage. I used an old WWII round meter that I've had in my junk box for years, 1ma full scale, and marked 0-5kv. Tacky, but bought and paid for long ago.

You'll notice also that the meter switch has an off position. On this particular wafer switch, there wasn't a lot of physical spacing between positions, and the off position isolates positions on the switch that are roughly 400v different in potential from one another. Had I allowed those positions to be adjacent, a flashover arc could have damaged the circuits.

I used meter shunts that would develop about .3v at full scale, and used variables to calibrate the various meter ranges.

The bias regulator is a simple zener/darlington combination, providing some regulation against variable grid current. The tube is cut off during standby with a 35K cathode resistor, which is bypassed by the cutoff relay during transmit.