Sensibly equivalent¶ to:
The catkin featured here has an external metal shield and is a brother to MH4 but this exhibit has a Marconi label.
Other MH4's in the collection are without this screening feature. The MH4 was designated as being for detector service in radio receivers. Catkin versions of the 1929 MH4 were introduced in 1933 and 1934.
The Marconi label testifies to the harsh treatment this valve has undergone. The wording at the top is Patented Made in England.
The outer metal shroud is 32 mm in diameter, and excluding the B5 base pins is 97 mm tall.
References: Data-sheet, 1005, 1043, 3002 & 1040. Type MH4K was first introduced in 1933.
Absolute Maximum Operating Conditions¶
Updated October 20, 2013. shape:catkin construction:pinch type:triode age:1930.1940 base:b5 heater:4.0v pins:5 pin:1.a pin:2.g1 pin:3.h pin:4.h pin:5.k