Sensibly equivalent¶ to:
M-OV had trouble designing the MPT4. Not only did it take them a clear two years to produce technically successful copies of Mazda's landmark AC/Pen but thereafter they had to redesign it several times (including the beam tetrode version MKT4) over the next 5 or 6 years.
This exhibit has a B5 base and side contact but also the later classic or shouldered shape envelope. We also have the earlier balloon envelope MPT4.
The Marconi paper label. The internal construction is obscured but has the same cylindrical anode and small top mica of the balloon version.
The classic envelope is 50 mm in diameter and, excluding the B5 base pins, it is 111 mm tall.
References: Private communication, data-sheet & 1040. Type MPT4 was first introduced in 1931. See also 1931 adverts.
Absolute Maximum Operating Conditions¶
Updated June 11, 2022.