Sensibly equivalent¶ to:
The valve shown is an MKT4/7, ie fitted with a B7 base cap. Most MKT4/5's were fitted with B5 base caps with the screen grid connected to a side terminal.
The MKT4 shown in the photo is a late (c. 1950) specimen and has a distinct Cossor look about it. It is probably a Cossor MP/Pen re-labeled as an M-OV valve.
The MKT4 was listed as a beam tetrode but this exhibit is a pentode with three wire grids.
In single ended audio configuration would provide an adequate 2.5 Watts.
Some pre-war EMI television receivers used the MKT4/7 as a line output valve.
It was a design that was produced by several different manufacturers. Note also that MP-Pen, MPPen, MP/Pen are variants describing the same type of valve.
The classic envelope is 53 mm in diameter, and excluding the B7 base pins, is 110 mm tall.
References: Data-sheet, 1043 & 1040. Type MKT4/7 was first introduced in 1937.
Absolute Maximum Operating Conditions¶
Updated April 21, 2020. shape:classic construction:pinch type:beam.tetrode age:1930.1940 base:b7 heater:4.0v pins:7 pin:1.- pin:2.g1 pin:3.g2 pin:4.h pin:5.h pin:6.k pin:7.a