The U84 is an interesting rectifier. The 1930s British standard of 4.0V at 1 Amp is used for the heater but the glass disc construction and the B8B base point to a post war product. The anode form and ribbon filament again suggest an earlier design. Look at the 80 for a comparison.
The maximum reservoir capacitor value is 16μF and the minimum effective series resistance must be at least 100 Ohms.
The paper label of the Marconi brand of M-OV. The anode is formed into a flat oval tube with a side flange that attaches to the supports. The anode is carburised and the filament is an oxide coated ribbon.
The wide glass tube envelope is 32 mm in diameter, and excluding the B8B base pins is 70 mm tall.
Reference: 1040. Type U84 was first introduced in 1947.
Absolute Maximum Operating Conditions¶
Updated February 21, 2014. shape:wide.glass.tube construction:glass.foot type:rectifier.fw age:1940.1950 base:b8b heater:4.0v pins:8 pin:1.ic pin:2.ic pin:3.a(2) pin:4.ic pin:5.ic pin:6.a(1) pin:7.h.k pin:8.h