The 3V4 audio output pentode was designed for use in battery portable radio receivers. Mullard describe their 3V4 equivalent as a battery operated output pentode with centre tapped filament, and designed for operation with equal voltages on both screen and anode.

The bright Nickel anode box is rectangular in cross section and obscures the grids. The filament is a pair of single strand loops and thereby passes through the grids four times. Tension for the filament is maintained by a spring at the top of the bulb and this is also the centre tap connection. At the base end two filament strands are connected to each connection.

The thin glass tube envelope is 18 mm in diameter, and excluding the B7G base pins, is 45 mm tall.

 
Pin Connections

B7G	1	2	3	4	5	6	7
	f-	a	g2	-	fct	g1	f+

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm	Pout	D
	1.4	0.1	90	90	-4.5	9.5	2.1	100,000	2.15	0.27	7%

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 02 July 2007