The TE474 from Dario is an AC mains variable μ amplifying pentode. The grid bias range is from -1.5 to -30.0 Volts. The initial introduction in 1934 was with a B5 base cap as shown above. In 1935 the TE474 was issued with a B7 base cap and the mutual conductance was increased from 2.0 to 2.3 mA/V.
The top cap with the screw connection was a feature of early 1930's valves and was phased out when the metal 'top hat' connection became popular in the mid 1930s.
This excellent shot shows the inner structure. Thanks to Mike Edwards for sending these images.
The balloon envelope is 52 mm in diameter, and excluding the B5 base pins is 131 mm tall.
Reference: 1043. Type TE474 was first introduced in 1934.
Absolute Maximum Operating Conditions¶
Updated August 04, 2013.