The 3B2 is a mystery and we have no operating details on this exhibit.

The cylindrical anode is taken to the top cap. The helical filament is visible in the picture and the top connection to the filament is via a central support rod. A third element is visible with a short stub of wire. It is not possible to identify if this third mounting rod housed a second filament or a control grid. The filament continuity is good.

The wide glass tube envelope is 38 mm in diameter and, excluding the base pins, is 101 mm tall.

This exhibit was last updated on 18 July 2007