The 12K8GT was purpose designed as a broadcast radio frequency changer valve. It 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.

See also 6K8.

The wide glass tube envelope is 28 mm in diameter and, excluding the IO base pins, is 70 mm tall.

 
Pin Connections

IO	1	2	3	4	5	6	7	8	tc
	m	h	a	g2-g4	g(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

Triode	Va	mAa
	100	3.8

Thanks to Frank Philipse for supplying the above datasheet

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