Sensibly equivalent¶ to:
This Marconi/Osram MH4 (MH4K) valve was a manufactured as a Catkin. The Catkin construction was derived from the large Cooled Anode Transmitting valves, and these also featured a shaped copper anode sealed to a glass envelope.
The date of the catkin design was 1933 and was clearly made for use in all-mains radio receivers.
The design was also with a conventional glass balloon envelope also with the designation MH4.
The thin metal tube envelope 25 mm in diameter and, excluding the B5 base pins, is 95 mm tall.
References: Datasheet, 1005, 1043, 3002 & 1040. Type MH4K was first introduced in 1933.
Absolute Maximum Operating Conditions¶
Updated February 07, 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