Here's a snippet from an article in the
Cleveland Plain Dealer on the 50th anniversary of the CT-100. It quotes Steve McVoy discussing the flange/baking-temperature issue associated with the ongoing 15GP22 rebuild effort.
When the picture tubes were manufactured, air was removed at room temperature by a vacuum machine. The picture tube then was heated in a 700-degree oven designed to excite the remaining air molecules so that as many as possible could be pulled out with the vacuum machine.
With time, the adhesive fails and air leaks through the seam. Restorers are experimenting with a new adhesive that has potential to keep air out for a long time, but the adhesive degrades at 500 degrees. Putting it in a 700-degree oven would not work.
"Right now, we don't know why 700 degrees is the magic number," McVoy said. "Was that the perfect temperature to remove all the air, or will something less than 500 degrees be enough?
"If it works, then we could have lots of tubes," he said. "I have four tubes and six sets that could use them." In addition to the RCA CT-100 and Model 5 prototype, several other brands of TVs of that era used the 15-inch color picture tube.
And another from the
CT-100 news & noticespage of my site.
09-05-2005...on the 15GP22 rebuild front, a new, custom-made cam that controls the slew rate of the baking temperature has been ordered. After a few more hurdles (probably most of them as yet unknown), the rebuild team will attempt an engineering evaluation run using a damaged 15GP22 before a bona fide attempt is made to bring a rebuildable tube back to life.
Quote:
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Originally Posted by Kaye-Halbert TV
...but we had two tubes that still had filament continuity re-evacuated. They lasted about a month. Charles
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Simply put, a month is plenty of time to slop on a bead of sealant and dry it. If the tube survives baking for that long
without the custom slue rate, old 15GP22's may soon be looking a lot brighter!