The ECH21 is an early all glass triode hexode frequency changer for radio. The B8B base has short equi-spaced pins and a metal spigot for alignment and to cover the envelope seal.

The oscillator triode was designed to produce 14 Volts peak to peak feed for the mixer section. The hexode portion is described by Mullard as suitable for AVC (AGC).

The wide glass tube envelope is 28 mm in diameter and, excluding the B8B base pins, is 61 mm tall.

 
Pin Connections

B8B	1	2	3	4	5	6	7	8
	h	a	a(t)	g(t)	g2-4	g1	g3	h

 
Absolute Maximum Operating Conditions

Triode	Vh	Ah	Va	mAa
	6.3	0.33	160	4.5

Hexode	Va	Vs	Vg	mAa	mAs	ra	gm
	250	100	-2	3.0	6.2	1.4M	0.75

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 10 June 2007 {find valves by name}