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X25

Sensibly equivalent to:
1AB6 1C3 DK96
See also:
Pentagrid Converters - Mullard 25 mA Series Advert, November 1954
    
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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.

 

Pin Connections
B7G
1
2
3
4
5
6
7
f-
a
g2
g1
g4
g3
f+,g5

 

Absolute Maximum Operating Conditions
Heptode
Vh
Ah
Va
Vs
Vg
mAa
mAs
ra
gm
1.4
0.025
85
68
0
0.6
0.14
0.8M
0.3
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated February 25, 2013.
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