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12SK7

Sensibly equivalent to:
CV543 VT-131
    
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The 12SK7 is a variable μ pentode for RF and IF amplifiers in superhet receivers. The gain of the device being controlled by a negative voltage derived from rectifying the final IF signal. In this way strong signals do not overload the receive chain because the various controlled stages have their gain reduced.
The 12.6 Volt heater was introduced so that the heater could be run directly from a vehicle battery. It would have been common to find these valves in professional mobile equipment. For fixed station use the 6SK7 was an identical device in all other respects.
This Mullard valve was made in the 1940s in America as UK manufacture was insufficient for the war effort. The Amerty name signifies this USA import.
The thin metal tube envelope is 25 mm in diameter and, excluding the IO base pins, is 50 mm tall.
References: Datasheet, 4055, 3002 & 1040. Type 12SK7 was first introduced in 1939.

 

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

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
12.6
0.15
250
100
-3
9.2
2.6
0.8M
2.0,
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated August 08, 2017.
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