The CV26 is a high voltage, low current beam tetrode with a thoriated tungsten filament. The 813 is the commercial designation.
Like many vintage valves the Cv26 has been used to build audio amplifiers. A single ended and triode connected valve would run successfully from an HT of 800-1,000 Volts.
RCA published an annotated diagram of the main components of the 813.
The valve base would be mounted on spacers so that a blower could be fitted under the chassis and a stream of forced air cooling would pass over the envelope.
The graphite anode is supported on ceramic insulators.
The shaped graphite anode has flat outer faces but the ends are rounded within.
The top insulator is ceramic and at the centre can be seen the two springs that maintain tension on the filament.
The UX7 base. The locating pip can be seen on the metal base shell.
The lower screen, lower ceramic insulator and a clear view of the graphite anode. The beam plate is just visible within the anode. It is a bright rectangular box that doubles as the screen and passes through the lower ceramic disc. At the appropriate place within the anode a window is cut out to allow the electrons to reach the anode.
The classic envelope is 63 mm in diameter, and excluding the UX7 base pins is 175 mm tall.
