Sensibly equivalent¶ to:
The MU12 is a directly heated full wave rectifier and it was a popular design that was also produced by other manufacturers. The MU12 and MU14 are the same valve made on the same production line. On post production testing the best were badged MU14 and those capable of a lesser performance became MU12's.
The anodes are flat sided whereas the MU14 in the collection has ridges pressed into the mesh for greater rigidity. The support is also of a different style, this clearly indicates that the two valves come from different productions. The MU12 seems the earlier device.
The Marconi logo label is stuck to the side of the envelope. The twin anode structure can be made out within the silvering of the glass caused by the firing of the getter.
The anodes are made from a fine wire mesh and support is provided by a central glass rod. The filaments are oxide coated metal ribbon formed into a single inverted V within each anode.
The balloon envelope is 56 mm in diameter and, excluding the B4 base pins, is 115 mm tall.
References: Data-sheet & 1043. Type MU12 was first introduced in 1933.
Absolute Maximum Operating Conditions¶
Updated January 22, 2013. shape:balloon construction:pinch type:rectifier.fw age:1930.1940 base:b4 heater:4.0v pins:4 pin:1.a pin:2.a pin:3.f pin:4.f