This article provides examples of GE (KEN-RAD) manufactured tubes.

GE was one of the most prolific tube manufacturers in US history, and many companies sold GE tubes repackaged under their own brand name. The GE factory EIA code number is “188″ and proves GE was the true manufacturer, although there are a few rare exceptions to the “188″ rule.  Here are several examples:

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This article provides examples of RCA-manufactured tubes.

RCA is probably the most famous tube manufacturer in US history, and many other companies sold RCA tubes repackaged under their own brand name. The RCA (EIA) code number is “274″ and proves RCA was the true manufacturer. Here are several examples:

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This article provides examples of CBS Hytron-manufactured tubes.

CBS Hytron was a very high quality USA tube manufacturer. Their production numbers were much smaller than the big name brands (RCA, Sylvania, GE).

The CBS Hytron (EIA) code number is “210″. When you find a repackaged CBS Hytron tube, you will most commonly find 6SN7GT and 6SL7GT. Here is an example:

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The article provides examples of Sylvania-manufactured tubes.

Sylvania was probably the most prolific American tube manufacturer, and their tubes were found packaged by many well-known USA name brands. Among the EIA codes that you will find on Sylvania-manufactured tubes are 312 and 722. Here are photographs to illustrate the wide diversity of companies that Sylvania manufactured for…

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