I find this interesting too. I was involved in high power microwave tube production in the early 90's. It was then a very viable market and may still be today. I'd be surprised if it made #4 for exports though.
Originally Posted by ic-racer
Major vacuum tube production stopped in the US in the mid 1980s. There is some hoax article floating around the internet indicating USA exports vacuum tubes. Current the majority of worldwide audio vacuum tube production is in Russa and China.
2005 USA vacuum tube production summary:
Richardson Electronics, LaFox, IL
Makes a 300B, 845 and 50 sold under the Cetron brand for high-end audio, as well as a KT88 sold under the National brand. Richardson has large quantities of tooling obtained from old American tube factories when they shut down. Also makes some larger transmitting and high-voltage types. Richardson markets many tubes, obtained from other factories worldwide, under their own brandnames; such as Cetron, National and Amperex.
Westrex Corporation, Kansas City, MO
Makes the reissued Western Electric 300B for high-end audio. Claims to be developing a KT88, WE308, WE274A and other old WE types for future manufacture. Corporate and sales offices are located in Atlanta and Chattanooga. Also has sales office in UK. Tube manufacturing facility was relocated from Kansas City to Huntsville, AL. This firm is independent of AT&T Corporation and has licensed the brandnames from AT&T.
MU, Oceanside, CA
Small contract factory, makes occasional runs of unusual glass and metal-ceramic tubes for military use. Still makes some of the old "Bendix Red Bank" tubes, such as the 6094 and 6384, in occasional lots.
Triton Services ETD, Gaithersburg, MD
Makes some Eimac and Litton glass power types, using equipment from the original manufacturers. Recently discontinued some glass types, such as 4-65A, 4-125A, 250TH, 304TH/TL, etc. (these types are now only available from China).
source -- http://www.vacuumtube.com/mfg.htm