The original PM12 was released in 1928, the 'A' replaced it in the early 1930s. This was a pure screen grid tetrode made by the azide process, where the screen was used to prevent instability in radio frequency amplifiers by reducing the grid to anode capacitance.

The early top caps were made as screw connectors as can be seen here. In later PM12A valves the familiar cap was introduced and the glass left clear to show off the new 'clean' oxide process.

The metalised classic envelope is 47 mm in diameter and, excluding the B4 base pins, is 114 mm tall.

 
Pin Connections

B4	1	2	3	4	tc
	g2	g1	f	f	a

 
Absolute Maximum Operating Conditions

Tetrode	Vh	Ah	Va	Vs	Vg	mAa	ra	gm
	2.0	0.18	135	75	-0	2.0	330,000	1.5

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This exhibit was last updated on 02 December 2007