This exhibit is labelled as a barium tube, clearly indicating an oxide cathode. The envelope also gives the heater voltage as 2.0 V and the anode voltage as 200 V. This valve is given as originally manufactured in 1929. The electrodes are pointed at an angle to the horizontal and the filament is a single 'V'.
The balloon envelope is 44 mm in diameter and, excluding the B4 base pins, is 86 mm tall.
Absolute Maximum Operating Conditions |