The HL22 is a high voltage control triode. The construction is not designed to dissipate much heat and this suggests a role as a driver. Possible applications include control or large thyratrons or as part of a high voltage stabilised power supply driving the series pass valve. Or it could have been for use as a shunt stabiliser for an EHT supply.

Looking onto the grid one can see the mesh and bell structure. It is though a planar triode has been stretched to accommodate the high voltage and the long pinch speaks also of insulation rather than high frequency use. In fact the design is the very opposite of high frequency design principles.

Looking into the bell of the grid, the oxide coated cathode is seen as a white rod under the mesh. The other small white structure is a mystery.

The wide glass tube envelope is 29 mm in diameter, and excluding the IO base pins is 111 mm tall.

This exhibit was last updated on 24 February 2008