AUDIO VALVES: U19 HEAVY DUTY HW RECTIFIER CV187 CV1508 U23 V1913 10E/520

The U19 is a high voltage half wave rectifier with a series resistance of 600 Ohms and a maximum input capacitance rating of 4 µF.  

The anode is carbonised to aid in radiating away the heat generated in use by the intense electron bombardment and the whole electrode structure smacks of longevity and build quality having been constructed with ceramic supports and insulators.    It is reassuringly vast at 166mm height.  Oram introduced this valve type for Air Ministry use in 1947.