Early Television
Early Television
Early Television
Early Television
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Early Television Museum

CRT Rebuilding

CRT rebuilding at the museum

Channel Master 1966 brochure (courtesy of Mark Oppat) RACS pyrex tube rebuilding
Clinton Electronics 12AP4 rebuilding activity RACS 15GP22 rebuilding
Color Champion rebuilding plant RCA CRT Manufacturing Training Manual
The Craft of CRT Rebuilding - video by Bob Galanter Recollections of a CRT rebuilder
CRT Rebuilding in Waco, Texas Dave Sager - Litton CRT glassblower
Empire Vacuum Products rebuilding plant W. O. Smith letter about thermal processing
General Electric CRT manufacturing brochure Southwest Technical Products aging schedule
Griffiths Electronics guns Superior Electronics article
Hawkeye Operating Procedures Nick Williams' rebuilding report from RACS
How its Made - Cathode Ray Tubes (YouTube video) Nick Williams: CRT Restorer by Brian Belanger (page 15)
The Last CRT Factory in Europe John Yurkon's project: making an all-glass 15GP22
Profits in PIcture Tube Rebuilding Video about rebuilding by Bob Galanter
Philips book on making CRTs (1939) 12AP4 rebuilding
A Precision CRT 1955 (YouTube video) 12AP4 substitute
Quality Testing of Cathode Ray and TV Tubes 15GP22 rebuilding project
RACS CRT rebuilding notebook  

In the 1950s and 60s, hundreds of companies rebuilt picture tubes. At that time tubes failed frequently, and rebuilding was an inexpensive alternative to buying a new one. Today picture tubes outlast the average TV set, and only a few companies still rebuild them.

Here is a brief description of the process:

1. The outside of the tube is carefuly cleaned, removing any labels and aquadag.

2. The neck of the CRT is cut off near the shell of the tube.

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3. If a replacement gun is not available, the old one must be rebuilt by inserting a new filament and cathode. The gun is then attached to a glass "stem", which contains the wire leads and a small protruding tube used to evacuate the CRT. Another approach is to use a new gun.

4. A glass extension tube is fused to the CRT neck.

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5. The stem (with the gun attached) is fused inside the extension tube. Then the tube is cut off at the stem.

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6. A vacuum pump is attached to the stem, and air is removed. When as much air as possible has been removed, the tube is heated to about 750 degrees F. This process causes the remaining air molecules to move very rapidly, increasing the likelihood that they will end up in the stem, where the vacuum pump can remove them.

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7. The tube on the stem is then crimped to seal the CRT.

8. There will be remaining molecules of gasses in the tube which must be removed. Barium is used for this purpose. The "getter", which is attached to the gun, is "flashed" to remove the remaining gas. This is done using an RF induction heater.

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9. A high voltage is applied to the anode and filaments of the tube to prevent future arcing.

10. The cathode is activated by applying different filament voltages for a period of time.

11. The base is installed, soldering the wires coming out of the gun and using silicone adhesive.

12. The tube is tested for emission and shorts.