The Brimar 5673 is a mystery. We believe that a batch of 5763s were made with a transposition in the lettering.
This exhibited was tested as a 5763 and measured exactly. The 5763 is a small transmitting beam tetrode valve for HF and low VHF use and is equivalent to the Mullard QV03-12.
The circular anode contains a flat sided cathode and grids that are flat across the cathode width and rounded at the ends. The screen grid wires are directly in front of each control grid wire.
The heater is referenced as 6.0 V by RCA, Brimar and Mullard.
John Fielding ZS5JF has sent the following information and the RCA data-sheet.
The 5763 was extensively used as an oscillator, multiplier or power amplifier in HF and VHF equipment. The old Marconi Instruments Q meter variable frequency oscillators used it, also used in the psu as a series regulator valve. The useful upper frequency limit is about 300 MHz. It was also used as a driver or PA in some early Pye Telecomms VHF mobile radios before being superseded by the twin tetrode QQV03-10 type of valves.
Thanks to Gus Cusick for sending this image.
The thin glass tube envelope is mm in diameter and, excluding the B9A base pins, is mm tall.
References: Data-sheet & 1040.
Absolute Maximum Operating Conditions¶
Updated January 05, 2022.