The CV1991 is electrically equal to the 6SQ7. It is a double diode triode sharing a common cathode.

The triode is seen at the top with the carbonised anode, the double diodes are seen as the bright anodes between the triode and the pinch. It was typical practice to have such diodes as single sided anode plates.

The clamping metal shell that covers the envelope/base junction has sprung loose.

It is probable that this valve was designed for superhet receiver use where the diodes would act as signal detector and AGC detector and the triode would be the first stage audio amplifier.

The wide glass tube envelope is 28 mm in diameter and, excluding the IO base pins, is 68 mm tall.

 
Pin Connections

IO	1	2	3	4	5	6	7	8
	m	g	k	a(d2)	a(d1)	a	h	h

 
Absolute Maximum Operating Conditions

Triode	Vh	Ah	Va	Vg	mAa	ra	gm
	6.3	0.3	250	-2	0.9	91K	1.1

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 04 June 2007 {find valves by name}