The MHLD6 was developed for military and professional applications which demanded valves rated to operate from 6 V supplies, notably vehicle batteries.

This was at a time, later 1930s, when domestic British AC mains radios still used valves with 4 V heaters.

The MHLD6 is also known by the pre-WWII RAF service designation of VR101.

The double diode triode was used in superhet radio receivers. The diodes would rectify both signal and AGC lines, and the triode would act as the first audio amplifier stage.

The classic envelope is 36 mm in diameter and, excluding the IO base pins, is 93 mm tall.

References: ¹⁰⁴³. Type MHLD6 was first introduced^¶ in 1940.

 
Pin Connections

IO	1	2	3	4	5	6	7	8	tc
	m	h	a	a(d2)	a(d1)	-	h	k	g1

 
Absolute Maximum Operating Conditions^¶

Triode	Vh	Ah	Va	Vg	mAa	ra	gm	μ
	6.3	0.635	200	-5	11.5	7,300	3.0