Sensibly equivalent¶ to:
The 7B7 is a high impedance variable μ amplifier pentode. It was probably designed for IF amplifier use, with a tuned anode circuit.
It is interesting to ask who made the valve. We believe that it is not Cossor as labelled. Construction details are typically American and we have seen Cossor-labelled valves of this vintage (c. 1950) clearly marked 'British Made' (as here) and (on the other side) 'made in USA'. Similar-looking valves were also factored under several other 'big-name' labels around this time.
The wide glass tube envelope is 27 mm in diameter and, excluding the B8B base pins, is 55 mm tall.
References: Private communication, datasheet & 1040.
Absolute Maximum Operating Conditions¶
Updated August 24, 2015. shape:wide.glass.tube construction:all.glass type:pentode age:1940.1950 base:b8b heater:6.3v pins:8 pin:1.h pin:2.a pin:3.g2 pin:4.g3 pin:5.s pin:6.g1 pin:7.k pin:8.h