The DK91 is a miniature B7G dry battery heptode, it was designed for frequency changer use in battery portable radio receivers. The valve was designed for self oscillating service.

The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 45 mm tall.

 
Pin Connections

B7G	1	2	3	4	5	6	7
	f-	a	g4,g4	g1	f-	g3	f+

 
Absolute Maximum Operating Conditions

Heptode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	1.4	0.05	90	67.5	0	1.6	3.2	0.6M	0.3

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 06 July 2007 {find valves by name}