The 7B5E is an audio output pentode designed for receiver applications.

The Loctal or B8B base was designed to allow a positive fixing into the socket for mobile applications. In the UK the 7B5E was made from 1950.

The 6K8GT is the same valve electrically but fitted onto an International Octal base.

The datasheet gives full operating details but generally the output power was just under 3 Watts for a distortion of 11%.

The base skirt has a location pip to ensure the correct alignment in the socket.

The identification is etched into the dome of the envelope.

The wide glass tube envelope is 29 mm in diameter, and excluding the B8B base pins is 55 mm tall.

References: Datasheet & ³⁰⁰². Type 7B5E was first introduced^¶ in 1939.

 
Pin Connections

B8B	1	2	3	4	5	6	7	8
	h	a	g2	-	-	g1	k	h

 
Absolute Maximum Operating Conditions^¶

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	6.3	0.4	315	285	-7	9.5	1.6	104,000	1.5

Thanks to Frank Philipse for supplying the above PDF datasheet