The MVSG from Cossor has a mirror finish inside the envelope from the magnesium gettering. Externally the envelope is covered with a metallic paint to add to overall screening.
Introduced in 1932, Cossor in 1935 describe the MVSG as a special variable-mu screened grid valve. The special feature being the control of volume by altering the grid bias. It is clear that variable-mu technology was still relatively novel.
The balloon envelope is 42 mm in diameter and, excluding the B5 base pins, is 120 mm tall.
References: Data-sheet & 1043. Type MVSG was first introduced in 1932.
Absolute Maximum Operating Conditions¶
Updated February 02, 2013. shape:balloon construction:pinch type:tetrode age:1930.1940 base:b5 heater:4.0v pins:5 pin:1.g2 pin:2.g1 pin:3.h pin:4.h pin:5.k pin:tc.a