The D77 is the Marconi equivalent of the Mullard EB91, and consists of two separate signal diodes in the envelope. The QD77 is a special quality version of this valve.
The diodes were designed for vision and sound detection in television receivers. Additionally they are recommended for limiting and DC restoration.
The Marconi Marconiphone consumer label. Our other Marconi D77 carries the MWT professional logo.
The insulated heater wire has been coiled into a double helix.
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 D77 was first introduced in 1949. See also1949 adverts.
