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FC4

Sensibly equivalent to:
15A2 41MPG A80 A80A CV2955 MX40 VHT4 VO4 X42
See also:
Mullard AC Mains Valves - Frequency Changing - Some Important British Valves
    
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The FC4 was the first British produced Octode, it was first made commercially in 1934. This exhibit carries the Mullard logo whereas FC4 does not.
The FC4 is a self oscillating mixer for frequency changing in radio superhet receivers. The oscillator has to generate 12 Volts peak to peak for correct operation. It would typically have used a 90 Volt oscillator anode voltage and up to 2.0 mA anode current. The oscillator would use g1 as control grid and g2 as anode. Of the six grids the final one was a suppressor, g3 and g5 would be screen grids, and the signal would be applied to g4, hence its position as top cap connection.
The rear is plain metalising paint.
The classic envelope is 45 mm in diameter and, excluding the B7 base pins, is 119 mm tall.
References: Datasheet, 4024 & 1043. Type FC4 was first introduced in 1934.

 

Pin Connections
B7
1
2
3
4
5
6
7
tc
g2
g1
g3,g5
h
h
m,k
a
g4

 

Absolute Maximum Operating Conditions
Octode
Vh
Ah
Va
Vs
Vg
mAa
mAs
gm
4.0
0.65
250
70
-1.5
1.6
3.8
0.6
PDF scanned from an original document held by the museum
Updated February 15, 2014.
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