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The 117N7GT is an audio output beam tetrode with integral half wave rectifier designed for American broadcast radios using a series heater chain.

The anode of the rectifier is connected to one side of the heater and thus to the mains line. The rectifier cathode would feet the HT smoothing circuit.

This combination valve would reduce the number of valves in a basic radio and thus lower the cost.

The International Octal base and pins.

Thanks to Mark Mallison for sending the images.

The thin glass tube envelope is  mm in diameter and, excluding the IO base pins, is  mm tall.

Reference: Data-sheet. Type 117N7GT was first introduced in 1940. See also 1940 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.