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CV1991

Sensibly equivalent to:
6SQ7GT
    
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The CV1991 is electrically equal to the 6SQ7 but the specification is for the Glass Tubular version 6SQ7GT. 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. One diode anode is the box and the other is formed from the two vertical rods.
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.
References: Datasheet, 1040 & 1043. Type CV1991 was first introduced in 1939.

 

Pin Connections
IO
1
2
3
4
5
6
7
8
m
g1
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 PDF datasheet.
Updated May 22, 2014.
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