Sensibly equivalent¶ to:
7A2 A70B AC/Pen APP4A CV1683 KT42 MP/Pen N40 P4VA Pen4VA
The valve shown is an MKT4/7, ie fitted with a B7 basecap. 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.
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: Datasheet, 1043 & 1040. Type MKT4/7 was first introduced in 1937.
Absolute Maximum Operating Conditions¶
Updated December14, 2012.