The Type D77 is the M-OV 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 screen is a flat plate in the centre. The diodes have two halves of the anode stitched together with a cylindrical column in the middle.
The folded stitches in the anode. The two plates both have four tabs that are held in the mica discs.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 47 mm tall.
Reference: Data-sheet & 1040. Type D77 was first introduced in 1949. See also1949 adverts.
