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6K8

Sensibly equivalent to:
CV1945
See also:
Metal Striptease - The 'Magic Three' Valves - Two New Converter Valves
    
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The 6K8 triode hexode valve was purpose designed as a radio frequency changer. The valve has a common cathode and is unusual within our collection in that the triode and hexode control grids are internally connected.
The local oscillator would produce 7.5 Volts peak to peak signal from the triode section.
The input signal would be coupled to the frequency changer via the top cap connection to grid 3.
As a metal enveloped valve the top cap connection is interesting. The connector is standard but is set in an insulating disk that is then sealed into a shaped end of the envelope. This appears quite difficult to manufacture.
The diagram shows the arrangement of the electrodes within the steel shell. This ingenious arrangement avoids the large number of concentric grids used in other mixer designs.
The thin metal tube envelope is 25 mm in diameter and excluding the IO base pins, is 60 mm tall.
References: Datasheet & 1040. Type 6K8 was first introduced in 1938.

 

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
6.3
0.3
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 22, 2016.
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