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.
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.
Donation from Unknown, Before 22 Mar 1995
On bulb: N/PHILIPS/D VI/Sold for amateur use only/3,5V/NOM Display block: TETRODE "Double Grid" Valve. D. VI./Philips. Made in Holland./Bright emitter, 3.5 V, 0.5 amps
Type of item
104 mm (Height), 55 mm (Outside Diameter)
Not including display block.
[Book] Tyne, Gerald F. 1987. Saga of the Vacuum Tube., 1987, 419 Pages