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.

The thin metal tube envelope is 25 mm in diameter and, excluding the IO base pins, is 50 mm tall.

 
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 datasheet

This exhibit was last updated on 12 June 2007 {find valves by name}