This exhibit made by Cleartron is both fascinating and a mystery. The fascination comes from the twin cylinder triode construction and the mystery comes from the fact that this valve contains no identification lettering beyond the manufacturers name.

The detail picture shows the twin narrow bore anode assembly. Within each anode is a helical wire grid joined together by a round bar above the anode. The filament is a single strand passing vertically through the centre of each anode. Each support for the lower end of the filament is brought out to a base pin. The top connections are made to a supporting frame that at first sight passes through the pinch to a base pin. Close inspection reveals that the wire passing through the pinch is not connected. This puts both filament sections in series.

The wide glass tube envelope is 40 mm in diameter, and excluding the B4 base pins is 102 mm tall.

This exhibit was last updated on 08 October 2006