The 20F2 screened RF pentode was designed for use in universal (ie no mains transformer) sets with a series connected heater chain. Mostly in television receivers at RF or as a sync separator.

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

References: Datasheet, ¹⁰⁴⁰ & ³⁰⁰². Type 20F2 was first introduced^¶ in 1949.

 
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 PDF datasheet

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