The 20F2 screened pentode was designed for use in universal (i.e. no mains transformer) sets with a series connected heater chain. Most probably in television receivers.

The thin glass tube envelope is 20 mm in diameter and, excluding the B8A base pins, is 52 mm tall.

 
Pin Connections

B8A	1	2	3	4	5	6	7	8
	h	a	s	g3	g2	g1	k	h

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	gm
	11.0	0.2	135	135	-1.3	27	6.5	10.6

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 12 June 2007 {find valves by name}