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PM3A

 
See also:
The Philips-Mullard (PM) Series - Mullard PM Filament Advert - Valves
    
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The PM3A was introduced in 1927 as a resistance capacity coupled amplifier triode with a μ of 35.
The identification details are etched onto the side of the envelope together with a code 7C68. The main details are also carried on a paper strip fixed above the Bakelite base. Looking up under the mirror of the Magnesium gettering reveals a horizontal box anode. This is supported from the pinch by stout wires that form a wide U. The anode is stippled.
The Balloon envelope is 43 mm in diameter, and excluding the B4 base pins, is 90 mm tall.
References: 1931 data-sheet & 1043. Type PM3A was first introduced in 1927. See also 1927 adverts.

 

Absolute Maximum Operating Conditions
Triode
Vh
Ah
Va
ra
gm
4.0
0.075
125
63,000
0.55
Thanks to Andy Cowley for supplying the above PDF datasheet.
Updated March 22, 2022.
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