866A High Voltage Power Supply

The high voltage (approx. 1150 VDC) B+ power supply has taken on various configurations over the last couple of years:

power-supply

hv-supply-2

But in both of the above renditions, a full wave rectifier with modern diodes was used.  To bring the power supply more in line with period practices, it was completely re-built and the modern diodes replaced with a pair of 866A Mercury Vapor tube rectifiers.  The output filter consists of a 20-4 H swinging choke, 5 uF oil cap (two 10uF / 1kV in series), a 8.5H choke, and 6 uF / 1.5 kV oil cap.  A 25K ohm / 100W bleeder is used and a 50mA ammeter connected to the cold end of the bleeder and ground.  Under normal conditions with no load, the current is 46mA, translating into about 1150 VDC.

866-supply-1200v