The VU508 is high voltage rectifier designed for high power applications. The U19 (M-OV) and the CV187 are essentially the same valve. When looking at the different interpretations of this specification from different companies the variations in construction are interesting. Here the design uses mica discs to hold the electrodes at the top and the bottom.
The valve also carries the old stores code of 10E/520.
The maximum reservoir capacitor that can be fed is 4 µF and the valve needs a minimum effective series resistance of 600 Ohms.
The Type designation is also found within an elliptical lozenge typical of M-OV production.
The anode has a central cavity and two side flanges that connect to the supports. The side flanges are positioned at the points of maximum heat production.
The filament is tensioned by coiled springs mounted above the two top mica sheets.
The pinch and lower fixings.
The classic envelope is 50 mm in diameter and, excluding the B4 base pins, is 162 mm tall.