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 three wire grids can be seen above the lower mica. The control grid is wound on copper rods and has a heat radiating fin above the top mica. The two part carbonised anode is stitched together.
The top mica has wire springs fitted that grip the inside of the glass.
The classic envelope is 44 mm in diameter and, excluding the UX6 base pins, is 103 mm tall.
References: Data-sheet, 3002, 1040 & 1043. Type 42E was first introduced in 1936. See also1936 adverts.
