Sensibly equivalent¶ to:
The SG215 tetrode was introduced in 1928 and was similar to the 1929 215SG. It is a screen grid or tetrode valve for RF amplification in broadcast radio receivers or the wireless as it was known at the time.
The original adverts show that it was initially fitted with a screw top cap. The 'top hat' top cap appeared in the mid 1930s.
The detail photograph is of the control grid. It has the appearance of being hand made rather than the perfectly regular structure expected of a machine wound grid.
The balloon envelope is 43 mm in diameter and, excluding the B4 base pins, is 117 mm tall.
References: 1040. Type SG215 was first introduced in 1928.
Absolute Maximum Operating Conditions¶
Updated October 06, 2018. shape:balloon construction:pinch type:tetrode age:1920.1930 base:b4 heater:2.0v pins:4 pin:1.g2 pin:2.g1 pin:3.f pin:4.f pin:tc.a