The 6A7 is an American Pentagrid converter or heptode mixer. The 6A8 is the same valve electrically but on an IO base. We also have the 6A7E in the museum.
This American valve was distributed in the UK by Brimar. 6A7 was distributed by Mullard. We believe that this indicates a valve from WWII.
The top mica and electrode top supports. The inner grids are copper and it can be seen that the first grid is notched to take the winding whereas the second grid is just two plain copper rods - these act as the oscillator anode.
The lower mica. The round cathode tube and the heater wires are the most clearly seen.
The classic envelope is 38 mm in diameter and, excluding the UX7 base pins, is 97 mm tall.
References: Data-sheet, 1040 & 1043. Type 6A7 was first introduced in 1933. See also1933 adverts.
