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X71M

Sensibly equivalent to:
12K8GT X76M
    
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The X71M is a triode hexode mixer for use with a series heater chain running at 160 mA. The almost equivalent 12K8GT also has a 160 mA heater but drops 12.6 Volts.
We also have the similar X76 which is metalised so in fact is an X76M.
The typical M-OV id lozenge. The final digit is unclear but the valve was confirmed as the X71M by testing the heater. This valve was once metalised as can be seen by the wire at the top of the image.
The top mica. The control grid has copper supports and is connected to the top cap by way of an auxiliary mounting strut, g2 and G4 are strapped together above the top of the g3 support rod.
The glass distorts the view from below. All that is clear is the heater connection.
The classic envelope is 38 mm in diameter, and excluding the IO base pins is 97 mm tall.
References: Datasheet, 1040 & 1043. Type X71M was first introduced in 1939.

 

Pin Connections
IO
1
2
3
4
5
6
7
8
tc
m
h
a
g2,g4
g1(t),g1
a(t)
h
k
g3

 

Absolute Maximum Operating Conditions
Hexode
Vh
Ah
Va
Vs
Vg
mAa
mAs
gm
15
0.16
250
100
-3
4.0
3.5
0.62

 

Absolute Maximum Operating Conditions
Triode
Va
mAa
100
3.8
Updated December14, 2014.
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