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EF40

Sensibly equivalent to:
CV3885
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Mullard describe the EF40 as a voltage amplifying pentode, primarily intended for use in high gain RC coupled AF voltage amplifier stages.
The B8A EF40 was developed into the B9A EF86.
The interesting thing about this exhibit is the BBC valve section sticker. IT shows the valve being tested in February and October 1953.
The thin glass tube envelope is 20 mm in diameter and, excluding the B8A base pins, is 52 mm tall.
References: Datasheet & 1040. Type EF40 was first introduced in 1948.

 

Pin Connections
B8A
1
2
3
4
5
6
7
8
h
a
ic
g3
g1
g2
k,s
h

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
mAs
gm
6.3
0.2
250
140
-2
3.0
0.6
1.8
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated January 03, 2019.
shape:thin.glass.tube construction:all.glass type:pentode age:1940.1950 base:b8a heater:6.3v pins:8 pin:1.h pin:2.a pin:3.ic pin:4.g3 pin:5.g1 pin:6.g2 pin:7.k.s pin:8.h
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