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.

 
Absolute Maximum Operating Conditions

Triode	Vh	Ah	Va	ra	gm
	4.0	0.075	125	63,000	0.55

This exhibit was last updated on 02 December 2007