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12K8

Sensibly equivalent to:
CV703
See also:
The 'Magic Three' Valves
    
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This Brimar exhibit was made in the USA but the original maker is not indicated.
The 12K8GT was purpose designed as a frequency changer valve for use in the broadcast bands.
The local oscillator would produce 7.5 Volts peak to peak signal from the triode section.
See also 6K8 that has a diagram of the construction.
The reverse of the steel envelope is plain black paint.
Sealing the top cap insulator to the metal envelope was an added complication of the metal valve design.
The thin metal tube envelope is 25 mm in diameter and, excluding the IO base pins, is 62 mm tall.
References: Datasheet, 1040 & 1043.

 

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
ra
gm
12.6
0.15
250
100
-3
2.5
6
0.6M
0.36

 

Absolute Maximum Operating Conditions
Triode
Va
mAa
100
3.8
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated October 15, 2019.
shape:thin.metal.tube construction:glass.disc type:triode.hexode age:1940.1950 base:io heater:12.6v pins:8 pin:1.m pin:2.h pin:3.a pin:4.g2.g4 pin:5.g1(t).g1 pin:6.a(t) pin:7.h pin:8.k pin:tc.g3
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