This is a very interesting power triode. The B7A base has only four pins fitted and there are no identifying marks on the glass.
The control grid is of a cage design that was latterly found in power valves of many power classes.
The design echoes that of the 15E UHF power triode but lacks the separation of anode and grid of the 15E. Perhaps this was also designed for pulse operation.
Looking along the length of the anode flange.
The heater connections.
The base lacks the thicker pin normally found on B7A valves, thus the valve can be inserted into a standard B7A valve-holder in any position. This suggests that a special holder was employed.
The top of the cage grid. The numbers 481 are stamped on the anode.
The wide glass tube envelope is 51 mm in diameter and, excluding the B7A base pins, is 51 mm tall.
