▼ Menu

    
Extras ▼

The BK oscillator valve dates to 1925 and it may never have had a proper type designation number. It appears to be experimental and was probably never fitted with a base.

The filament is a single thin thread. The grid is a helical wire supported only by its ends, and both ends are brought out to separate top pins. Unusually the anode is also a helical wire. It too is supported only at the ends and again both ends are brought out to separate top pins.

The Balloon envelope is 53 mm in diameter and, excluding the base pins, is 80 mm tall.

Reference: Observation. Type BK was first introduced in 1925. See also 1925 adverts.