The U12 directly heated full wave rectifier was a popular design that was also produced by other manufacturers. It is believed to date from 1932.

Initially the U12 and the U14 were the same valve. 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.

In the picture the type designation on the top of the envelope has the central type number omitted. The Type Number U12 is stamped (not etched) in large white letters on the side.

The classic envelope is 48 mm in diameter and, excluding the B4 base pins, is 105 mm tall.

 
Pin Connections

B4	1	2	3	4
	a(1)	a(2)	f	f

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	mAa
	4.0	2.5	350	120

Thanks to Frank Philipse for supplying the above datasheet

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This exhibit was last updated on 02 December 2007 {find valves by name}