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PM12A

Sensibly equivalent to:
218SG 220SG S215B S22 S24
See also:
The Azide Process - 2 Volt Valves for Battery Receivers
    
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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.

 

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
PDF scanned from an original document held by the museum
Updated January 31, 2013.
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