This month is rectifier time. Meet the 274 family of tubes.
The 274 is a classic full wave rectifier tube with two diodes in one bottle sharing the same cathode. It was introduced by Western Electric in the 1930ies.Western Electric data sheet specifies a maximum of 4 uF of load capacitance. While the original WE274A data sheet lists a maximum rectified output current of 140mA, this was later uprated to 225mA when the WE274B was released. In 2017 Deutsche Elektronenröhren Manufaktur GmbH released the ELROG ER274A and ER274B as modern versions which can replace the original tubes. While the Western Electric 274s used oxide coated filaments the ELROG 274s use thoriated tungsten.
Here we see the ELROG ER274A and ER274B
Both versions share the same construction and only differ in the base.
The ELROG rectifiers use a vertical arrangement of the two plates while other manufacturers mount them side by side.
They come in the straight sided glass bulb and construction which is characteristic for ELROG tubes.
Of course a post about the 274 would not be complete without also showing a Western Electric tube.
Here we have a WE274A with engraved base, a very rare item.
Some details of the tube:
And now as always some photos with tubes glowing.
The thoriated tungsten filament of the ER274A is clearly visible at daylight.
And more so at night:
I hope you enjoyed this tube of the month post with both vintage and modern versions of the 274 rectifier. You need more output current or want to load the rectifier with more capacitance? Stay tuned for next months tube presentation.