The literature indicates that Mullard made the HL13 in two versions. We have the Ct8 based type but a B7 base option also existed and this is described in the datasheet. What we have here is a third version based on a B5 base.

Mullard describe this valve as an indirectly heated medium impedance triode for use in DC/AC mains receivers. The use for the valve would have been as an RF amplifier in radio receivers.

The classic envelope is 36 mm in diameter and, excluding the B5 base pins, is 103 mm tall.

 
Pin Connections

B5	1	2	3	4	5	6	7	8	tc
	m	h	h	k	-	-	-	a	g1

 
Absolute Maximum Operating Conditions

Triode	Vh	Ah	Va	Vg	mAa	ra	gm
	13.0	0.2	200	-3.7	5.0	12,000	3.3

Thanks to Frank Philipse for supplying the above datasheet

More

This exhibit was last updated on 03 January 2008 {find valves by name}