Sensibly equivalent¶ to:
The DK96/X25 dry battery frequency changer from M-OV under the Marconi name is from the later range of very low filament consumption valves introduced in 1954. This example is British made.
These 25 mA filament valves were designed for use in battery portable domestic radio receivers. This type of radio was killed off by the transistor portable in the early 1960s.
The anode is bright nickel as it is a low power valve, but note the heat dissipating fins on the grid supports. All the grids are wire wound.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 47 mm tall.
References: Datasheet & 1040. Type X25 was first introduced in 1954.
Absolute Maximum Operating Conditions¶
Updated February 25, 2013. shape:thin.glass.tube construction:all.glass type:heptode age:1950.1960 base:b7g heater:1.4v pins:7 pin:1.f- pin:2.a pin:3.g2 pin:4.g1 pin:5.g4 pin:6.g3 pin:7.f+.g5