The 6AS7G is a double triode with special properties. The AC anode resistance is very low at 280 Ω and the mutual conductance is considerable at 7.5 mA/V. This valve could be used in low voltage power supplies as a series pass device or it could be used for a direct drive audio amplifier. Use as a series element in a stabilised power supply was probably the original use.
each anode is a pair of finned flat U channels either side of the cathode assembly.
The earliest reference we found was in the 1950 RCA data book.
Looking into the anode channels with the grid windings slightly wider than the anode.
Looking along the grid axis. The control grids have curved radiating fins at the top. The heater wire is coiled before being coated with insulating ceramic.
Side view showing the support rods in the sides of the anode and the grid support attaching to the top fin.
The classic envelope is 50 mm in diameter and, excluding the IO base pins, is 119 mm tall.
References: Data-sheet & 4040. Type 6AS7G was first introduced in 1946. See also1946 adverts.
