The ubiquitous red valve. This amplifier pentode was a general workhorse. It was extensively used in radio and radar during WWII. This example was made in America but carries the pre CV VR designation of an RAF receiving valve.

The pins are equi-spaced around the circumference of the pin circle.

The dimensions are 32 mm in diameter for the body of the screening can, and 60 mm in length, excluding the short B9G pins and the central spigot that locates the pins and covers the evacuation seal.

References: Datasheet & ¹⁰⁴⁰. Type VR91 was first introduced^¶ in 1938.

 
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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