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The VR105/30 here called a VR-105 is a cold cathode voltage stabiliser. The details of its operation are given in the type designation. This tube will stabilise the voltage across it to 105 Volts for output currents between 5 mA and 30 mA. To strike the tube the voltage must exceed 135 V.

As with all such stabilisers the voltage will vary slightly with the current drawn. For this tube the stabilisation is 4 Volts across the current range.

If used as a reference within a stabilised power supply the stabiliser tube would be run as close as possible in constant current mode, i.e. with a fixed load and controlling the voltage on the control grid of the amplifier within the power supply.

Seen obliquely the supporting micas can be seen. Unlike the older balloon envelope design the classic and tubular envelopes allowed for the mica supports to be firmly held by the glass envelope.

The wide glass tube envelope is 38 mm in diameter and, excluding the IO base pins, is 88 mm tall.

References: Data-sheet & ¹⁰⁴⁰. Type VR105/30 was first introduced in 1939. See also 1939 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.