The AC/VP1 is a variable μ screened pentode designed for mains radio receivers. The variable μ characteristic enables automatic gain control of RF and IF amplifiers in superhet receivers.

The AC/VP1 and AC/VP2 were the standard RF/IF screened pentodes in the Mazda range for AC mains radios from the mid-1930s until domestic radio manufacture was interrupted by WWII.

The two valve types were essentially identical except that the AC/VP1 has its anode connected to the top cap, as with most screen-grid valves. The AC/VP2 has the control grid (g1) connected to the top cap, as was standard for later IF pentodes.

The B7 version was introduced in 1939 and this, the B5 based version, is earlier. Thanks to Simon Balderson for sending these images and details.

The B5 base showing the compression pins with leads soldered to the bottom of the pin.

The side of the consumer box showing basic operating details.

The top of the box showing that the valve is the B5 variant.

The classic envelope is 39 mm in diameter and, excluding the B5 base pins, is 108 mm tall.

References: Datasheet & Simon Balderson. Type AC/VP1 was first introduced^¶ in 1934.

 
Pin Connections

B5	1	2	3	4	5	tc
	g2	g1	h	h	k	a

 
Absolute Maximum Operating Conditions^¶

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	4.0	0.65	250	250	-2.8	7.4	1.85	1M	2.0

Thanks to Frank Philipse for supplying the above PDF datasheet

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