Space charge valve. This valve is a tetrode but not a screen grid type. The inner grid is positively biased to neutralise the space charge and the outer grid is the control grid. This structure was designed to allow operation at low plate voltages.

3.5 volt directly heated cathode. 3.5 volt filament at 0.5 amp. anode and extra grid at 2 to 10 volts.Tthe additional space charge was between filament and control grid and was connected to metal shell of a 4 pin English base. The type number is written DVI, meaning D6.

The double grid principle was/first patented by H.J.Round in 1919./The extra grid was given a positive/potential thereby allowing the use/of a lower anode voltage.

Physical Description

Spherical glass bulb with top exhaust tip and European style 4 pin base with a brass shell. A side terminal on the shell connects to the inner 'space charge' grid.

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