Antique radios, Old Time Radios

7AK7


			Tube type:	Vacuum Pentode

Tube ID = 5126


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Identical to	7AK7
First Series	1948 en.wikipedia.org/wiki/Vacuum_tube

Base	Octal (Int.Octal, IO) K8A, USA 1935
Was used by	Technology / Measurement
Filament	Vf 6.3 Volts / If: 0.8 Ampere / -: Indirect /
Description	From Wikipedia: "To meet the reliability requirements of the early digital computer Whirlwind, it was necessary to build special "computer vacuum tubes" with extended cathode life. The problem of short lifetime was traced to evaporation of silicon, used in the tungsten alloy to make the heater wire easier to draw. Elimination of the silicon from the heater wire alloy (and paying extra for more frequent replacement of the wire drawing dies) allowed production of tubes that were reliable enough for the Whirlwind project. The tubes developed for Whirlwind later found their way into the giant SAGE air-defense computer system. High-purity nickel tubing and cathode coatings free of materials that can poison emission (such as silicates and aluminium) also contribute to long cathode life. The first such "computer tube" was Sylvania's 7AK7 of 1948. By the late 1950s it was routine for special-quality small-signal tubes to last for hundreds of thousands of hours, if operated conservatively. This reliability made mid-cable amplifiers in submarine cables possible."
Tube prices	0 Tube prices (visible for members only)
Literature	Essential Characteristics, GE 1973


	Internet Miguel Angel Trujillo-Rodriguez

ARRL Handbook 1972
Michael Schlör

Raytheon Manual
Heinz Höger

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7AK7

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