The EF8 valve is a variable μ amplifier pentode with a fourth grid.

The variable μ amplifier pentode would be used in the AGC controlled stages of superhet receivers.

Our exhibit has the distinctive red of Mullard and is labelled Philips, the parent company. The dimensions are identical to the Mullard version and the Ct8 base was much more popular on the continent than in the UK and so it is probably that both were made on the same Dutch production line.

See EF8 for more details.

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

References: Datasheet, ¹⁰⁴⁰ & ¹⁰⁴³. Type EF8 was first introduced^¶ in 1938.

 
Pin Connections

Ct8	1	2	3	4	5	6	7	8	tc
	m	h	h	k	g4	g2	g3	a	g1

 
Absolute Maximum Operating Conditions^¶

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	6.3	0.2	250	250	-2.5	8	0.25	2.0M	1.8

Thanks to Frank Philipse for supplying the above PDF datasheet

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