Sensibly equivalent¶ to:
The valve shown is an MKT4/7, i.e. 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.
In single ended audio configuration would provide an adequate 2.5 Watts.
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 top view: the beam plates are strapped together at the top, the control grid has copper supports and heat radiating flanges.
The classic envelope is 44 mm in diameter, and excluding the B7 base pins, is 101 mm tall.
References: Data-sheet, 1043 & 1040. Type MKT4/7 was first introduced in 1937. See also 1937 adverts.
Absolute Maximum Operating Conditions¶
Updated January 03, 2022.