EF9 @ The Valve Museum

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EF9

Sensibly equivalent^¶ to:

CV1427

See also:

Mullard Red E Series - Mullard Red 'E' Series Advert - Mullard EF8, ECH2, EBC3, EF9, EB4, EL3 & AZ3 Advert - Red E Valves

Extras ▼

Mullard G8LSD Valve Collection Other EF9 exhibits

The EF9 is a variable μ amplifier pentode.

The variable μ amplifier pentode would be used in the AGC controlled stages of superhet receivers, IF and for HF receivers also RF amplifiers.

The EF9 is electrically identical to the IO based EF39, additionally the EF9 is pin compatible with the EF5 and has a higher voltage gain.

Our exhibit is unused, and has the distinctive red painted Mullard external metallisation screening.

We acquired two other EF9's that had belonged to the BBC.

The Label is dated 4 July 1940 and shows a measured mutual conductance of 2.65, a figure better than the published value.

The classic envelope is 29 mm in diameter and, excluding the Ct8 base pins, is 84 mm tall.

References: Data-sheet, ¹⁰⁴⁰ & ¹⁰⁴³. Type EF9 was first introduced in 1938. See also 1938 adverts.

Pin Connections

Ct8	1	2	3	4	5	6	7	8	tc
	m	h	h	k	g3	nc	g2	a	g1

Absolute Maximum Operating Conditions^¶

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	6.3	0.2	250	250	-2.5	6	1.7	1.5M	2.2

Thanks to Frank Philipse for supplying the above PDF datasheet.

Updated January 09, 2022.

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