I am frequently asked by B&K and Hickok owners to explain how to replace a #83 tube with a solid state version. This question is popular because #83 tubes are scare and expensive. Other benefits are increased reliability (no tube to wear down), less heat generated inside the tester case, and less load on the power transformer. So, if you want to Do-It-Yourself, I will explain how these replacements are made.

I will preface this tutorial with a few caveats: First, this procedure is easier to implement with B&K testers than Hickok testers. Hickok factored in the load that the real #83 tube has on the power transformer, and sometimes you cannot properly set the line without circuit modification. Keep this in mind if you plan to try it with your Hickok — you may be getting in over your head. Hence, substitution may be more effort than it is worth, especially when some Hickok buyers do not want the modification and would have to undo the circuit mods that were made. This leads to the second caveat: not everyone feels that the solid-state substitution works ‘excellent’ in Hickok’s. In fact, some “purists” will not even use a Hickok with a solid-state #83 replacement. They cite the fact that silicon diodes have less voltage drop than a tube rectifier, and feel that the tube test results will not be “pure.”

Personally, I always use a solid-state replacement for B&K testers. For Hickok, I prefer to use a real #83 tube only because circuit modifications are sometimes necessary, which makes going back to a real #83 difficult for the tube tester owner or future buyer. That said, I have no disapproval with using a solid-state #83 in a Hickok, and have found that any tube “test score” differences are trivial. In my opinion, the people who argue about small test score variations are really over-thinking the purpose of testing a tube — the end-result is NOT a test score, but to ascertain whether the tube will work satisfactory in your circuit. Common sense and practicality are important.

Here it goes…

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Discolored getter flashing (brown or black marks) does not mean that a tube was used. This fiction is believed by both uninformed buyers and seasoned tube jockeys. This myth seems credible because some new tubes have perfect shiny mirror getter flashing; therefore the assumption is that brown or black stains in the getter flashing must indicate a used tube. The myth says that the more brown/black discoloration, the “more used” the tube is. Wrong.

Excerpt from Electronics Magazine

The purpose of the tube getter and flashing is to remove gas inside the tube envelope during manufacture. This discoloration myth can be quickly debunked by reading the article in Electronics magazine, October 1950, entitled “Getter Materials For Electron Tubes”. The article explains that if the getter is vaporized very slowly during the manufacturing process, “the first barium atoms evaporated will absorb the gas present so that the remaining getter is deposited in a very high vacuum, exhibiting a shiny mirror.” If the getter was flashed very rapidly during manufacturing, then “the getter mirror will be discolored due to the dispersion of the barium.” The article then explains that the discoloration “does not mean that the getter is contaminated, but merely that the deposit is finely divided and therefore absorbs light.”

Several photos of NOS tubes below demonstrate this myth.  Likewise, I provide photos to demonstrate how the flashing looks when a tube is actually used. Let us proceed…

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Here is a rare tube — a Marathon MX-280 Globe #80 rectifier tube featuring MESH PLATES construction!  Not only that, but each section tests very strong Emission, comparable to an NOS #80!

In 18 years of collecting, I do not remember ever seeing another Mesh Plates #80 tube.  Look at that Glow!  You can see right through the Mesh Plates into the filament!  This would be a beautiful tube for any serious collector.  You could really impress your friends with this one.

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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:

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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:

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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. 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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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:

• 111 = Amperex
• 158 = DuMont
• 188 = GE / KEN-RAD (188-4, 188-5, 188-20, etc.) [info]
• 210 = CBS Hytron [info]
• 247 = National Union [info]
• 274 = RCA [info]
• 280 = Raytheon [info]
• 312 = Sylvania [info]
• 322 = Tung-Sol (USA)
• 323 = United Electronics
• 336 = Western Electric
• 337 = Westinghouse
• 722 = Sylvania-manufactured for OEM equipment makers (Allen Organ…)
• 1022 = Fisher branded Mullard/Telefunken/Amperex
• 1109 = Raytheon (Japan)
• U.S.A.3 (found on the glass envelope) = Tung-Sol
• Xf1,Xf2,Xf3,Xf4 = Mullard
• 7C,8I = Toshiba (Tokyo Shibaura Electric)

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.