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The 85 triode valve would be used in radio reception equipment. The diodes are for signal use and probably would be for AGC and AM signal detection. The triode would act as AGC amplifier or first audio amplifier, probably the latter.

The same characteristics and heater but with an IO base are found in 6V7G. The same characteristics but with a 2.5 V heater are found in Type 55.

The cathode tube runs vertically through both parts of the valve. The lower screening box, connected to the cathode, contains the two diode anodes, each anode is just a vertical rod. The upper black anode is formed with a cylindrical cavity that houses the cathode and grid.

The classic envelope is 35 mm in diameter and, excluding the UX6 base pins, is 97 mm tall.

References: Data-sheet, ¹⁰⁴⁰ & ¹⁰⁴³. Type 85 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.