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The DY802 is an EHT rectifier for monochrome TV service as colour television tubes usually required 25 kV EHT. This exhibit carries the later stylised Mullard logo.

The 1.4 Volt heater was designed to be run from a winding on the transformer supplying the EHT. This would be an HF transformer similar to the line output transformer of a television receiver.

The DY802 is designed for a maximum PIV of 30,000 Volts and will produce an output voltage of 20,000 Volts. The maximum reservoir capacitor is 0.003 μF.

Typical EHT rectifier construction - bell anode supported from the top and heater/cathode at the base.

The heater enters the lower end of anode and the side support connects the cathode at the top of the cathode tube. The cathode is strapped to one side of the heater to minimise the stress on the h/k insulation. The 1.4 Volt heater voltage would be generated from an overwind on the line output transformer.

Microscope image of the heater entering the cathode tube.

The thin glass tube envelope is 22 mm in diameter and, excluding the B9A base pins, is 66 mm tall.

Reference: Data-sheet. Type DY802 was first introduced in 1965. See also 1965 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.