The CV1331 is a battery operated variable μ screened pentode. The most direct commercial type was the Mazda VP23. It was probably used as an RF or IF amplifier in portable radio receivers.

The classic envelope is 32 mm in diameter and, excluding the MO base pins, is 81 mm tall.

References: Datasheet & ¹⁰⁴³. Type CV1331 was first introduced^¶ in 1938.

 
Pin Connections

MO	1	2	3	4	5	6	7	8	tc
	f	-	a	g2	g3	m	-	f	g1

 
Absolute Maximum Operating Conditions^¶

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	2.0	0.05	120	60	-1.5	1.45	0.5	1.45M	1.08

Thanks to Frank Philipse for supplying the above PDF datasheet

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