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EF40

Sensibly equivalent to:
CV3885
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The EF40 is 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.
This exhibit has most of the white lettering including the words Foreign Made. The seal between the pressed glass foot and the envelope is typical Philips.
The glass has a moulded skirt with location pip.
The gaps in the screen show all three grids and the strap connecting the two halves of the anode.
The thin glass tube envelope is 20 mm in diameter and, excluding the B8A base pins, is 57 mm tall.
References: Data-sheet & 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 October 26, 2020.
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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