Initially the U14 and the U12 were the same valve intended to meet all HT requirements up to a maximum of 120 mA at 500 V, using a capacitor-input filter. However, some valves performed better than others on final factory test so the best ones were graded and marked U14 whilst the also-rans were marked U12.This U14 was designed to work with a maximum reservoir capacitor of 32 µF and to have an effective series resistance of 100 Ω.
The M-OV identification ellipse with the Type designation along the long axis.
Microscope image of the lettering.
The remains of the Marconi Brand label.
The twin sections with stitched blackened anodes. The filaments are connected in series.
Face view showing how thin the filament ribbon is.
Under the microscope the filament tape weld to the support is clear.The balloon envelope is 45 mm in diameter and, excluding the B4 base pins, is 99 mm tall.References: Data-sheet & private communication. Type U14 was first introduced in 1931. See also 1931 adverts. |
