The original MS4 dates to 1929 and the first production was with the then standard screw top cap as here. The MS4B glass version was issued before the catkin version MS4B that was issued in 1933/4. Later production was again in a glass envelope but with the classic shouldered shape rather than the earlier balloon.
MS4B is a tetrode from the early mains valve era with its 4 Volt heater and it offered 'maximum amplification', whereas the earlier MS4 was a general purpose screened grid valve. The screened tetrodes and pentodes were employed for RF and IF amplification.
The Osram paper label.
The gettering has a small uncoated patch through which part of the construction can be seen.
The screen is visible. The outer plain metal holds a flat mesh within. SeeMS4B for a clear view of the construction methods.
The typical early 1930s screw top cap. The 'top hat' top connector became standard from the mid 1930s.
The balloon envelope is 44 mm in diameter and, excluding the B5 base pins, is 125 mm tall.
References: Data-sheet & 1040. Type MS4B was first introduced in 1931. See also1931 adverts.
