Initially the U14 and the U12 were the same valve intended to meet all HT requirements up to a maximum of 120 mA at 500V, 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 Ohms.![](../pics/aaq0160a.jpg)
This U14 has the earlier balloon envelope but also solid anodes.![](../pics/aaq0160b.jpg)
The dome of the envelope has etched markings but nothing in the centre of the circle.![](../pics/aaq0160c.jpg)
The lower end of one anode and the glass rod support in the centre.![](../pics/aaq0160d.jpg)
One rectifier segment: the ribbon filament and its support spring.The balloon envelope is 57 mm in diameter and, excluding the B4 base pins, is 117 mm tall.References: Data-sheet & private communication. Type U14 was first introduced in 1931. See also 1931 adverts. |