The 42E is an audio output pentode, with a low output rating. It is in fact a Type 6F6G on a UX6 base.
When used in push pull a pair would deliver 18.5 Watts in class AB2.
The classic envelope is 42 mm in diameter and, excluding the UX6 base pins, is 99 mm tall.
References: Datasheet, 3002, 1040 & 1043. Type 42E was first introduced in 1934.
Absolute Maximum Operating Conditions¶
Updated February 01, 2013. shape:classic construction:pinch type:pentode age:1930.1940 base:ux6 heater:6.3v pins:6 pin:1.h pin:2.a pin:3.g2 pin:4.g1 pin:5.k pin:6.h