The EF50 was one of the 'wonder' valves of WWII making possible high frequency IF strips (45 MHz) for Radar. It was also a relatively short lived valve and was thus manufactured in vast quantities.

Here we have an example of one made by Tungsram.

The wide glass tube envelope is 30 mm in diameter, and excluding the B9G base pins is 60 mm tall.

References: Datasheet & ¹⁰⁴⁰. Type EF50 was first introduced^¶ in 1939.

 
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 PDF datasheet

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