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The 6K7 pentode was designed for intermediate frequency amplifiers in 'modern' superhet type receivers during the mid 1930s. A couple of years later the slightly changed single ended version 6SK7 appeared.

This exhibit is unusual as it is New Old Stock and in perfect condition.

It is high impedance allowing for a high Q in the tuned anode circuit. It has a long grid base allowing for the stage gain to be altered according to the grid bias applied. Thus this a variable-μ valve where the gain is to be controlled by and AGC voltage developed at the detector stage. This was usually an additional diode. Typically within a double diode triode such as the 6Q7.

See also 6K7G for the glass envelope version.

The 6K7 (commercial designation) was called the VT-86 (Vacuum Tube) when purchased by the American Government.

The RCA logo.

Adding a top seal to the metal envelope was not ideal from a manufacturing point of view.

The hard glass disc at the base of the envelope has wires on the outside that solder into the pins set into the Bakelite base cap.

The thin metal envelope is 25 mm in diameter and, excluding the IO base pins, is 63 mm tall.

References: Data-sheet & ¹⁰⁴⁰. Type 6K7 was first introduced in 1936. See also 1936 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.