Sensibly equivalent¶ to:
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.
This exhibit has a plan screen whereas DF91 has a perforated outer screen.
See also 1T4.
The screen obscures the inner detail but at the top the tops of the grids are visible. The grid support rods are of increasing diameter to provide the inter grid spacing.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 46 mm tall.
References: Datasheet & 1040. Type DF91 was first introduced in 1947.
Absolute Maximum Operating Conditions¶
Updated September 25, 2019. shape:thin.glass.tube construction:all.glass type:pentode age:1940.1950 base:b7g heater:1.4v pins:7 pin:1.f- pin:2.a pin:3.g2 pin:4.ic pin:5.f- pin:6.g1 pin:7.f+