Sensibly equivalent¶ to:
The Ferranti ZD is a double diode. References 1040 & 1043 give the heater rating as 7 Volts at 200 mA but other sources place the heater requirement at 13 Volts at 200 mA. One has to be incorrect but when in a current limited series heater chain the effect is the same.
The bright box is a screen connected to the cathode. The diode anodes are the two rods seen either side of the cathode.
Thanks to Han Bex for sending these images.
The balloon envelope is mm in diameter and, excluding the B5 base pins, is mm tall.
References: Data-sheet & 1043. Type ZD was first introduced in 1936. See also 1936 adverts.
Absolute Maximum Operating Conditions¶
Updated February 22, 2017.