8A1 @ The Valve Museum

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8A1

Sensibly equivalent^¶ to:

4046A 5A/128B AC/S2/Pen AC/SG CV1282 E446 HP4101C MS/Pen MSP4 SP4 SPT4A VR124

Extras ▼

Brimar Photographic Donation - Mark Mallison Other 8A1 exhibits

The 8A1 is a screened RF pentode. Brimar say that the valve is best employed where the input voltage does not greatly exceed 0.5 Volts.

The 8A1 B5 base version was introduced in 1933 with the 8A1 B7 base version in 1937.

The reverse has the identification 4046A on the plain zinc screening paint.

The B5 base pins are of the two part type with the top section split open and central pin sealed at the lower end.

Thanks to Mark Mallison for sending the images.

The balloon envelope is mm in diameter, and excluding the B5 base pins is mm tall.

References: Data-sheet, Data, ¹⁰⁴⁰ & ¹⁰⁴³. Type 8A1 was first introduced in 1933. See also 1933 adverts.

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	1.0	250	100	-1.5	3.0	-	0.375M	4.0

Thanks to Frank Philipse for supplying the above PDF datasheet.

Updated September 18, 2022.

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