The Y220 is an output tetrode based on the Harries patent. By setting the anode at a specific multiple of the cathode to g2 distance the valve maximised the efficiency of a power tetrode. The geometry also reduces the effect of secondary electrons dislodged from the anode and thus reduced the tetrode kink. M-OV further developed the work of J Owen Harries and by adding a pair of beam plates emulated the effect of the suppressor grid and removed the need for the large size anode. The critical distance output valves were thus a product of the early to mid 1930s but were overtaken by the developments of the beam tetrode.
The anode is 30 mm in diameter.
The Hivac name and Type designation is etched into the dome.
The shape of the screen grid showing the flat region across the filament. The control grid has the same pitch and the wire is placed midway between the screen grid wires.
The filament has four strands within the grid region and is in the shape of an M.
The classic envelope is 45 mm in diameter, and excluding the B5 base pins is 97 mm tall.
Reference: 1043. Type Y220 was first introduced in 1935.