The ubiquitous red valve, and this exhibit is clearly not in mint condition. This amplifier pentode was a general workhorse. It was extensively used in radio and radar during WW2.

Mullard, the UK arm of the Dutch multinational Philips, describe the EF50 as being fully controlled by a grid voltage of 0 to -6 or 0 to -55 Volts, according to the circuit configuration.

The pins are equi-spaced around the circumference of the B9G pin circle. The central base spigot houses the evacuation seal as well as guiding the valve correctly into the base.

The wide glass tube envelope is 32 mm in diameter and, excluding the B9G base pins, is 60 mm tall.

 
Pin Connections

B9G	1	2	3	4	5	6	7	8	9
	h	g2	a	g3	s	k	g1	s	h

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	6.3	0.3	250	250	-2	10	3	1.0M	6.5

Thanks to Frank Philipse for supplying the above datasheet

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This exhibit was last updated on 10 June 2007 {find valves by name}