The 3A5 is a double triode with a centre tapped filament. The two sections in series would run from 2.8 Volts at 0.11 Amps. Although it could be used for RF amplification it would be mainly used as an audio power amplifier. With both sections operated as Class B push-pull the valve would produce an output of 2 Watts.

From the side, the flat oval of the anode is clear. The anode is blackened and this is unusual in battery valves.

The thin glass tube envelope is 17 mm in diameter, and excluding the B7G base pins is 46 mm tall.

Reference: Datasheet. Type 3A5 was first introduced^¶ in 1942.

 
Pin Connections

B7G	1	2	3	4	5	6	7
	f	a(1)	g1(1)	fct	g1(2)	a(2)	f

 
Absolute Maximum Operating Conditions^¶

Triode	Vh	Ah	Va	Vg	mAa	ra
	1.4	0.22	135	-	-	8,300

Thanks to Frank Philipse for supplying the above PDF datasheet

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