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EF9

Sensibly equivalent to:
CV1427
See also:
Mullard Red 'E' Series Advert - Mullard EF8, ECH2, EBC3, EF9, EB4, EL3 & AZ3 Advert
    
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The EF9 is a variable μ amplifier pentode.
The variable μ amplifier pentode would be used in the AGC controlled stages of superhet receivers, IF and for HF receivers also RF amplifiers.
The EF9 is electrically identical to the IO based EF39, additionally the EF9 is pin compatible with the EF5 and has a higher voltage gain.
Our exhibit is unused, and has the distinctive red painted Mullard external metalisation screening.
We acquired two other EF9's that had belonged to the BBC.
The Label is dated 4 July 1940 and shows a measured mutual conductance of 2.65, a figure better than the published value.
The classic envelope is 29 mm in diameter and, excluding the Ct8 base pins, is 84 mm tall.
References: Datasheet, 1040 & 1043. Type EF9 was first introduced in 1938.

 

Pin Connections
Ct8
1
2
3
4
5
6
7
8
tc
m
h
h
k
g3
-
g2
a
g1

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
6.3
0.2
250
250
-2.5
6
1.7
1.5M
2.2
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated January 31, 2013.
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