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  #1  
Old 12-01-2005, 12:21 AM
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Eric H Eric H is offline
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Rebuilt 15GP22's?

Picked this up from the A.R.F. Site.

Amongst other things they claim to be able to rebuild the 15GP22.

Anyone know about this place? I wouldn't mind having a 3KP4 rebuilt.

http://www.wmicronics.com/rebuilttubes.htm
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Old 12-01-2005, 12:57 AM
Steve K Steve K is offline
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Eric:

That can not be correct. Pete Deksnis has been involved in a 15GP22 rebuilding project for the last several years and they are just finding a way that might work. The rebuilding progress can be followed on his site. I am sure that if some company was already doing that he would have known. I can't wait until someone does find a way!

Steve
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Old 12-01-2005, 01:15 AM
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Ummm...why do you s'pose it would be listed along with the two early 21" round color tubes among "black & white picture tubes" they claim to rebuild? At first glance, less than credible to say the least.
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  #4  
Old 12-01-2005, 03:12 AM
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No way, I'm afraid at this time. There have been many attempts to rebuild 15GP22s, and all have been unsuccessful. As was explained to me several years ago by Gino at MetroColor, the metal flange on the 15G will separate from the bell of the tube as soon as they try to heat it. They tried, with donor 15Gs from Ed Reitan, Gary Miller, and myself. And back in the late 80s, Gary Hough and I tried an experimental rebuild with Dunbar. We couldn't get the 15G gun, but we had two tubes that still had filament continuity re-evacuated. They lasted about a month. The best explanation of "why not?" came from the guys at MetroColor, who have been there since the 50s, and held government contracts and met all ISO guidelines. In other words, they know their tubes. To rebuild the tube, the oven will have to be modified to heat at a precise rate and at a precise temp. There are also many other problems.

Bottom line, be skeptical of anyone who claims they can do it. UNLESS it is one of the women who worked on the original assembly line for the 15GP22, LOL...

Charles
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Old 12-01-2005, 08:50 AM
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i call bs.
and the big problem with these tubes breaking in the oven is likely due to the complex mask parts and their different rated of expansion.
the mg seal is usually where they leak so no surprise they fail upon heating.
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Old 12-01-2005, 09:42 AM
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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:
Originally Posted by Kaye-Halbert TV
...but we had two tubes that still had filament continuity re-evacuated. They lasted about a month. Charles
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!

Last edited by Pete Deksnis; 12-01-2005 at 10:24 AM.
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Old 12-01-2005, 11:20 AM
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Wonder how they made th' damthings in the first place ? You mean back in prehistoric 19-fackin'-54 they did somethin' we can't do today, w/all our glorious tecknologically & such ?!? Of course, maybe they were a-feared of pissing off David Sarnoff...I hear he didn't exactly suffer fools gladly....-Sandy G.
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Old 12-01-2005, 11:50 AM
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If RCA originally designed these tubes, you would think there would be archives somewhere of the tube designs and how to manufacture them.

I would think it would be cheaper to manufacture brand new tubes than to break so many in existance trying to find a way to put a new phosphers and gun assembly in an old shell...
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Old 12-01-2005, 12:06 PM
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When GE bought them the archives were trashed! At least this is I heard in the past. RCA was then bought by Thompson and now by a Chinese company.
I would say that only the name survives.


polaraman
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Old 12-01-2005, 02:06 PM
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Makes me wonder if a new all-glass crt based on the later 21" tubes would be at all pracitical. It would be terribly expensive & I think that would kill it. Probably one of those things that would cost $10,000 per unit to cover the setup costs. And then it wouldn't be original.

The discussion of the adhesive is interesting. There are some amazing epoxies being made but I don't know how they work as far as heat. This may be a silly question, but I wonder if modern plastics have advanced to the point that a PLASTIC crt could be made? Thats kinda hard to imagine, I know. If it could somehow be done that would do quite a lot to reducing setup costs. That would have to be some tough plastic, though, wouldn't it?
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Old 12-01-2005, 06:46 PM
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Has anyone (with a little bit of CRT knowledge) thought to call Western Micronics and inquire about the 15gp22 rebuild process? Hell... it couldn't hurt to ask... and it would shed some light on whether or not these yahoos got all of their marbles!

There is always the possiblity (although unlikely) that they might actually have an "all-wise all-knowing big giant head" with the secret to this tube.
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  #12  
Old 12-01-2005, 07:34 PM
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Some time ago I tried to contact them. Their phone had been disconnecteed.
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  #13  
Old 12-01-2005, 09:35 PM
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Quote:
Originally Posted by Steve McVoy
Some time ago I tried to contact them. Their phone had been disconnecteed.
Apparently, this would not be a good sign!
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Old 12-02-2005, 01:21 AM
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[QUOTEWith 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. tube back to life.[/I][/QUOTE]

So why can't they bake the tube with the old, less-than-ideal sealant that can take the 700 degrees with no problem, then seal THAT seal over with the stuff that will not eventually leak?
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  #15  
Old 12-02-2005, 01:30 AM
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Ed (AK user Colortel) told me about 25 years ago in this quest that a "frit" (unsure spelling???) was a piece of special glass that could be laid around the circumference of the tube at the seal that would transmutate into the glass and metal with heat during rebuilding.

Ed, if you read this, maybe you could refresh my memory, enlighten us and elaborate on that? I had kind of forgotten the conversation...

Charles
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