The ECH84 is a low voltage triode heptode. The ECH84 was specifically designed for operation as a sync separator in negative-modulation television receivers, the dual control feature of the heptode allowing the supression of noise that would otherwise cause sync errors.

The triode heptode could be also used as a frequency changer for medium and long wave radio receivers. The heptode has a straight characteristic that makes it suited as AM modulator.

See also the car radio frequency changer ECH83.

The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins, is 56 mm tall.

References: Datasheet & ¹⁰⁴⁰. Type ECH84 was first introduced^¶ in 1960.

 
Pin Connections

B9A	1	2	3	4	5	6	7	8	9
	g3	g1	k,g5,s	h	h	a	g2,g4	a(t)	g1(t)

 
Absolute Maximum Operating Conditions^¶

Heptode	Vh	Ah	Va	Vs	Vg	mAa	mAs	gm
	6.3	0.3	135	14	0	1.7	0.9	2.2

Triode	Va	Vg	mAa	ra	gm
	50	0	3.0	13.5k	3.7

Thanks to Frank Philipse for supplying the above PDF datasheet

More