The EY91 is a low power half wave rectifier. It uses the normal 6.3 Volt heater supply.
The valve needs a total circuit series resistance of 100 Ohms and can supply a 100 µF reservoir capacitor.
As would be expected the inner surface of the nickel sheet anode is bright. Only the outer surface is required to maximise heat radiation by being black in colour.
Face view of the anode.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 45 mm tall.
References: Data-sheet & 1040. Type EY91 was first introduced in 1948. See also1948 adverts.
