This article provides examples of NATIONAL UNION-manufactured tubes.
NATIONAL UNION was another quality USA tube manufacturer with most production dating from 1930s to 1950s. Their production numbers were significantly smaller than the big name brands (RCA, Sylvania, GE).
The NATIONAL UNION (EIA) code number is “247″. Here is an example:
This post provides examples of Raytheon manufactured tubes.
Raytheon was an extremely high quality USA tube manufacturer with prolific output, covering both civilian issue and a vast majority of US Military parts production. The Raytheon (EIA) code number is “280″.
Here is an example:
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:
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:
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:
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…
It is quite common to find tubes that have a “brand name” printed on them, but were actually manufactured by a different company. Yes, you can easily find “RCA” tubes made in a Sylvania factory, “GE” or “RCA” tubes manufactured in a Tung-Sol plant, etc.
So how do you know which company actually manufactured your tube? Most tubes have a Factory Code on them, an EIA code (Electronic Industries Association), and that code tells you the answer.
Here are the most common factory code numbers found on tubes:
Examples:
(1) you have an “Admiral” tube with “188-5″ codes. GE made your tube.
(2) You have an RCA 5881 with “U.S.A.3″ code on the glass. Tung-Sol made your tube.
There are many other “clues” also. For example, many Sylvania 12AX7A tubes have the tube designation printed in white-gray letters, vertically stacking all three designations of “12AX7A ECC83 7025″ Only the Sylvania factory used this exact marking.
It just looks like an RCA...
Sylvania markings.
distinctive markings of the Sylvania 12AX7A
Example: Stacked printed designation “12AX7A ECC83 7025″.
Here is an example of unique Sylvania-manufactured designation for 12AX7A tubes, where the tube is printed as “12AX7A ECC83 7025″ vertically stacked. In this example, this tube is branded as an RCA, but was in fact manufactured by Sylvania. Compare to the Sylvania-labeled tube.
When I have more time, I will continue to add more clues here to help you determine who manufactured a tube when it does not have a factory code number.
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