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The VU111 is also known as a CV1111. Although the commercial U27 was originally an M-OV type, this specimen (VU111) was supplied by Ediswan Mazda.

At one time CV1111's and equivalents were two a penny at War Surplus junk shops. This testified to the very large numbers made during WWII and to the fact that they have little or no civilian or amateur use. So what were they for? We have come to the conclusion that they were used, probably in pairs, to rectify HT supplies for pulse modulators for the magnetrons in airborne radar sets. However, there never seemed to be comparable numbers of pulser valves or magnetrons on the surplus market.

This high voltage high power half wave rectifier can deliver 125 watts. A pair producing 250 Watts could feed a high voltage low current transmitter output stage. A pulse modulator for a Radar transmitter needs high peak power but on average the power is quire modest. The U27 was rated at a maximum Peak Inverse Voltage (PIV) of 14 kV.

The anode is separated from the six vertical filament strands by a 5 mm gap, and is supported on substantial ceramic insulators.

The classic envelope is 50 mm in diameter and, excluding the B4 base pins stands 121 mm tall.

References: Data-sheet & ¹⁰⁴³.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.