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The Osram N77 is a miniature audio output pentode. In single ended configuration it will produce 1.4 Watts, suitable for a small broadcast receiver.

If used in push pull an output of 4 Watts is possible, but this valve was not expected to be used for hi-fi and for a radiogram there would be sufficient space to specify a physically larger valve. Output valves in the B7G base format ran very hot and not ideal if space existed for a larger envelope.

The control grid has radiating fins.

The thin glass tube envelope is 18 mm in diameter and excluding the B7G base pins, is 46 mm tall.

References: Data-sheet & ¹⁰⁴⁰. Type N77 was first introduced in 1953. See also 1953 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.