The EY83 is a miniature efficiency diode for use in television receivers to recover energy from the flyback period of the line timebase. The energy stored in the transformer is passed back to the HT rail to charge the reservoir capacitor.
Brimar state that the heater/cathode insulation is such as to remove the requirement for a separate transformer winding for the heater.
The side view of the anode. The inner surface of the metal is bright as can be seen from the turned-out ends.
The broad face of the anode is blackened for improved radiation efficiency. The heater leads are thickly insulated and separated from the cathode wall by a helical support wire.
The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins is 91 mm tall.
References: Datasheet & 1040. Type EY83 was first introduced in 1946.