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This Mullard copy of an American metal valve was made in Canada. The case is painted the distinctive red associated with Mullard. Valves that Mullard had made in the USA and Canada in the 1940s were all marked Amerty.

The whole point of the 6L7 is to ensure maximum isolation between oscillator and signal, and to provide a mixer which is efficient at VHF where stable oscillation would require a separate VHF oscillator triode.

For applications where a self-oscillating mixer (i.e. pentagrid converter) could provide adequate performance there were other Octal types specifically designed for this purpose.

The oscillator injection needed to be 18 Volts peak to peak. The signal feed to the top cap is typical of the period to improve signal isolation.

The thin metal tube envelope is 24 mm in diameter and, excluding the IO base pins, is 61 mm tall.

References: Data-sheet, ¹⁰⁴⁰ & ¹⁰⁴³. Type 6L7 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.