RCA UX-213 "Rectron" Tube

The UX-213 was developed by GE and marketed through RCA.  It was introduced in September 1925 as a full-wave rectifier for use in radio receivers.  To the best of my knowledge, no production radio was designed around this tube.  Its only appearance was in external AC-operated power supplies generally known as "B-battery eliminators", such as the obscure RCA AP-937 unit.

The UX-213 used a thoriated tungsten filament.

It was on the market for only about a year and a half, and not widely used, so it is quite rare today.  In May 1927, it was superseded by the more robust UX-280 which, in its various formats, remained in continuous production for a longer period than any other tube.  An interesting Westinghouse prototype tube marks a middle point between the 213 and the 280.


Most of the UX-213 tubes have the rectangular plate configuration as seen in the first picture.  In a group of tubes that had been the property of a engineer at the RCA Laboratories in Princeton, NJ, I found an example of the UX-213 with oval plates, as seen in the second picture.  Along with this tube were several other developmental rectifiers, one of which can be seen here.

The oval plate version is identical to the rectangular plate version in all other respects, including the UX-213 type number marking and the RCA logo at the top.  Keep in mind that in this period, RCA did not manufacture tubes, they only resold tubes made by Westinghouse or GE.

Prior to the introduction of the UX-213, there was a series of developmental versions that were designated as the UV-213.  At the number implies, these had the short-pin UV base, and examples have been found both with brass and Bakelite bases.  The UV-213 was never marketed.

The UX-213 came into being as a redesign of the UV-213 in mid-1924 to increase the power output capability of the tube.  According to internal GE documents, samples of the redesigned tube were submitted to RCA in February,1925, and the design was eventually released for sale in September, 1925.

All other references to the UX-213 that I have seen show (or mention) only the rectangular plate version, I conclude that the oval plate version is either a prototype or an early production version of this tube.  It may, in fact, be one of the sample tubes that GE submitted to RCA.

For more information and pictures of the UV-213, refer to this article on Bill Condon's excellent tube site.

Along with the UV-213, and of similar design, GE was apparently working on an AC-powered amplifier tube.  A sample of this tube can be seen here