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The E2217 is an experimental valve from M-OV. This exhibit carries the professional brand label of GEC.
The use is a mystery, is the device a gas filled radiation sensor? or just a rectifier.
A closer look shows a bright cylinder with a single thin strand wire at the centre. The wire is held in tension by a top spring. This suggests a filament. In fact it connects between pins 2 and 7 and at 1.4 Volts draws 500 mA and glows bright orange.
The filament top connection is supported in the two mica discs but the separation from the anode is small. The distance between the filament and the anode is much larger - about 7 mm. If this was an EHT rectifier, one would expect a better level of insulation.
The annular top mica with the open top of the bright anode cylinder.
Looking down on the top of the valve. The clamping of the filament wire suggests that the wire is tungsten or thoriated tungsten.
The wide glass tube envelope is 29 mm in diameter and, excluding the IO base pins, is 91 mm tall.
Reference: Observation.


Updated March 14, 2021.
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