The DY802 is an EHT rectifier for monochrome TV service as colour television tubes usually required 25 kV EHT. Pinnacle as a distributor sourced valves from many manufacturers. Here all we know from the word Foreign is that it was made outside the UK.
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.
The central oxide coated cathode with insulated heater within.The heater insulation is helical indicated a coiled wire within.
The thin glass tube envelope is 21 mm in diameter and, excluding the B9A base pins, is 65 mm tall.
Reference: Data-sheet. Type DY802 was first introduced in 1965.
Absolute Maximum Operating Conditions¶
Updated March 10, 2018.