The Mullard experimental EL5070 beam tetrode is a very high mutual conductance power valve with an anode dissipation of 10 Watts. It was designed for wideband video amplification.
Both wire grids are of the frame grid type to give very fine control over spacing and flatness of the wires passing over the cathode. The control grid wire is so fine that it can only be seen under a glass.
Although the connections are different and it has no top cap the E55L is electrically identical to this valve. The E55L was thus a construction more suited to volune production.
Looking face on to the screen grid. The beam plates are either side and the anode has a width of less than a third the width of the screen grid.
Turned through 90 degrees the anode is in two sections either side of the grids.
Here the beam plates can be seen to be part of the top and bottom shields. The anodes are both joined to the top cap but not to each other.
This micrograph shows the screen grid above the cathode. Between the thick lines of the screen grid winding are six fine control grid wires.
The wide glass tube envelope is 28 mm in diameter and, excluding the B9D base pins, is 61 mm tall.
Reference: Data-sheet. Type EL5070 was first introduced in 1965. See also1965 adverts.