The X42 is a vari-μ heptode oscillator and mixer or frequency changer. A design known in America as a pentagrid converter.
The oscillator and mixer share a common electron stream. g1 is the oscillator control grid with g2 acting as the oscillator anode. G3 and g5 are screening grids and the signal is applied to g4 via the top cap.
M-OV describe the X42 as having a carbonised bulb and therefore does not require external metallisation.
The Osram brand printed on the base cap. The main image shows the oval etched information panel on the glass.
The top mica showing the round cathode tube, plain rods that act as the oscillator anode and the copper connection from g4 to the top cap.
The classic envelope is 41 mm in diameter and, excluding the B7 base pins, is 101 mm tall.
References: Data-sheet, 1040 & 1043. Type X42 was first introduced in 1936. See also1936 adverts.
