DF91 @ The Valve Museum

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DF91

Sensibly equivalent^¶ to:

1F3 1T4 CV785 W17

See also:

1T4 Exploded

Extras ▼

Ever Ready Terry Collard Valve Collection Other DF91 exhibits

Every Ready were the market leading supplier of batteries for portable radios in the UK. Filament, grid bias and HT batteries all carried the Every ready name in the 1950s and 1960s. Once Ever Ready produced their own valves but eventually all of their valves were made and supplied by Mullard.

The DF91 is a is a miniature screened pentode for dry battery operation. It was designed for broadcast radio reception and is a variable μ RF device.

The bright anode with a glimpse of the wire grids within.

See also 1T4

The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 46 mm tall.

References: Data-sheet & ¹⁰⁴⁰. Type DF91 was first introduced in 1947. See also 1947 adverts.

Pin Connections

B7G	1	2	3	4	5	6	7
	f-	a	g2	ic	f-	g1	f+

Absolute Maximum Operating Conditions^¶

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	1.4	0.05	90	67.5	0	3.5	1.5	0.5M	0.9

Thanks to Frank Philipse for supplying the above PDF datasheet.

Updated October 24, 2016.

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