Sensibly equivalent¶ to:
218SG 220SG S215B S22 S24
The PM12A is a most interesting valve, one of the early oxide valves from Mullard. As a contrast see the earlier PM12A with the gold paint masking the blackening caused by the azide process.
The anode consists of two small plates on a saddle of stout wire and connected to the top cap. The control grid has almost the same area as the anode plates and is threaded by a single inverted V of filament. The screen grid and suppressor grids are larger than the control grid / anode for maximum electrostatic isolation.
The classic envelope is 42 mm in diameter and, excluding the B4 base pins, is 110 mm tall.
References: Datasheet & 1043. Type PM12A was first introduced in 1932.
Absolute Maximum Operating Conditions¶
PDF scanned from an original document held by the museum
Updated January 31, 2013.