Summary

Alternative Name(s): Thermionic Valve; Electron Tube; Vacuum Tube

High vacuum triode with unusual planar electrode structure and catenary filament. 2.7 volt directly heated cathode.
Filament voltage 2.7 volts at 0.5 Amp. 80 to 100 Volt on anode. Amplification factor is about 10. Marked "Telefunken DRP. Type EVN171 no. 56721". Used as low frequency amplifier.

The letters EVN stand for Empfänger, Verstärker, Niederfrequenz; meaning Receivers, Amplifiers, Low-frequency.

Physical Description

Cylindrical glass bulb on distinctive Telefunken 4 pin base. This base has 3 male pins and a hollow pin to make a female connection. Horizontal planar electrode structure with a circular disc anode with a helical grid above it and a catenary filament (open) above that. The structure is supported by two glass rods and stabilised by a pair of glass beads. Each of the leads passing through the pinch has a short length of platinum wire to ensure a good glass to metal seal. Valve is mounted on a display block.

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