Sensibly equivalent¶ to:
The W31 is a variable-μ RF pentode on a B7 base and designed for use on a 300 mA series heater chain in universal (AC and DC) mains sets.
The W31 is pin compatible with the Catkin W30 but has a higher specification.
Looking under the extensive silver gettering the only clear detail is of the heater entering the round cathode tube, The cathode is fixed to a lower screen.
The classic envelope is 44 mm in diameter, and excluding the B7 base pins is 119 mm tall.
References: Datasheet, 1040 & 1043. Type W31 was first introduced in 1935.
Absolute Maximum Operating Conditions¶
Updated August 29, 2018. shape:classic construction:pinch type:pentode age:1930.1940 base:b7 heater:300ma pins:7 pin:1.m pin:2.g1 pin:3.g3 pin:4.h pin:5.h pin:6.k pin:7.g2 pin:tc.a