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The VU133 is a high voltage half wave rectifier. It is unusual in that it has two anode cavities connected in parallel to the top cap. This design feature is a characteristic of the Ediswan-Mazda factory.

The high voltage characteristic is denoted by the internal ceramic insulators.

In keeping with similar HV rectifiers for pulse transmitter service the characteristics include a maximum peak anode current, in this case 400 mA. The maximum working Peak Inverse Voltage is 6,500 Volts with an off load PIV of 7,000 Volts. This rectifier requires a total series equivalent resistance of 850 Ohms and the reservoir capacitor should not exceed 1 μF.

For late 1930s equipment a 1 μF capacitor working at around 3,000 Volts would be a significant device in its own right. A 600 Volt 2 μF paper capacitor I once had, was in a grey/green can about 60 x 30 x 60 mm. To obtain the equivalent of 1 μF at 3,000 volts with a safety margin would take a bank of 18. Six series sets of three in parallel. Plus resistors to equalise the voltages.

The high voltage dictates the use of ceramic insulators. The cathode tube is seen in the centre of the anode.

The anode has cylindrical end shapes to increase the radiating area.

The anode construction is clear to see. The cathode is held centrally in the centre of the anode. Note the side flanges on the centre section.

The cathode top support attaches to rods that are set at right angles to the anode supports for maximum separation.

The classic envelope is 55 mm in diameter and, excluding the B4 base pins, is 122 mm tall.

References: Data-sheet & Private communication.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.