Yikes! Another CT-100 !

[jeyurkon]

Originally Posted by jr_tech

http://cgi.ebay.com/RCA-First-Produc...item27b0a3ba65


not affiliated,
jr

I see it went for $2,290. A bit more than I would have guessed.

John

[WA3WLJ]

Turbo - Vacuum pump it once then seal the nipple (AGAIN) , there Wouldn't be a constant running noise because; the 'General David' sucked it out once in 1954, Just re - SUCK back down to 1 X 10-8 again and RESEAL with VAC - U - SUCK
"SEAL" AND - IT - MIGHT Last another 50 Y E A R S !!!!!!

[ohohyodafarted]

This is, in theory, and I emphasize "in theory" something that might possibly work. However, the real problem would be in tapping into the old stub of the pinchoff in the base, connecting up to it for the pump down, and then somehow sealing the pinchoff without losing the vacuum.

IN the real world, when a tube is pumped down, it is done through a 4 inch length of glass tubing that sticks out the base of the tube where the wires exit. That 4" long tube is connected to the vacuum pumping system. After the tube has been properly evacuated, an electric heating element that was placed around the glass tube, right up next to where the wires exit, is turned on. IT heats the glass tubing up to the melting temperature, and the vacuum inside the tubing causes the molten glass to colaps, thus sealing the tube. the remanant of the 4 inch long glass tube is snapped off right where the tubing made the "pinch off" seal.

I personally cant see how you would tap into and then seal off a crt in the method you propose. It would be easier to just re-gun teh thing and do a conventional rebuild, and that way you have a real rebuilt crt with NEW emission to boot.

The issue if rebuilding the 15GP22 is going to be solved. You just have to have faith. "So let it be written...so let it be done"

[miniman82]

I had an idea on how to fix it, though I must admit I think more like a machinist than the electrician I really am. Sometimes that can be a good thing, though I have yet to lay hands on a 15GP22.

Seems to me the welded seal is the problem for many of the tubes, so why not get rid of it entirely? I mean, if there's a metal rim embedded into the glass, could you not just trim it back flush with the glass, then mate the 2 glass parts of the CRT together the same way neck glass is attached?

One other thing that I wonder about, is why if the metal part was leaking would you attempt to fix the leak by any other process but welding? I mean really, if 1954 welders could do the entire tube rim with a TIG torch, what's stopping those with rim leaks from sealing up a little pinhole? Is it really that difficult, or do tube people really not think that way RCA did back then?

To me, even difficult problems usually have very simple solutions...

[jeyurkon]

Originally Posted by miniman82

I had an idea on how to fix it, though I must admit I think more like a machinist than the electrician I really am. Sometimes that can be a good thing, though I have yet to lay hands on a 15GP22.

Seems to me the welded seal is the problem for many of the tubes, so why not get rid of it entirely? I mean, if there's a metal rim embedded into the glass, could you not just trim it back flush with the glass, then mate the 2 glass parts of the CRT together the same way neck glass is attached?

One other thing that I wonder about, is why if the metal part was leaking would you attempt to fix the leak by any other process but welding? I mean really, if 1954 welders could do the entire tube rim with a TIG torch, what's stopping those with rim leaks from sealing up a little pinhole? Is it really that difficult, or do tube people really not think that way RCA did back then?

To me, even difficult problems usually have very simple solutions...

The welded seal is also the Ultor HV connection, so you can't just eliminate it.

John and Bob, and Jerome, have done a lot of research. Probably your other questions will be answered at the ETF convention.

John

[Eric H]

I think the problem is the heat from a welder would cause the glass to break, but I don't know if the two halves were joined after the glass was attached to the metal flanges or after?

[ohohyodafarted]

Originally Posted by Eric H

I think the problem is the heat from a welder would cause the glass to break, but I don't know if the two halves were joined after the glass was attached to the metal flanges or after?

Eric,

The glass components were likely made by someone like Corning, and the Kovar ultor rings were fused to the glass at the the glass factory. The front and rear sections were delivered to RCA as a completed sub component, with the Kovar ultor rings already attached to the glass.

Due to the way the Kovar ultor ring is fabricated, there is not enough heat transfer from the weld to the glass to cause breakage. In fact the mechanical design of the Kovar ultor ring was designed the way it was, specifically to take into account the prevention of heat transfer to the glass.

There is also mention in literature pertaining to the general design of Kovar components for crt's, that in some cases, copper heat sink rings could be employed to prevent heat migration. We however, have no evidence one way or the other if copper heat sink rings were used at RCA in the welding process. In the only photo of the welding process at RCA, there does not appear to be the use of copper heat sinks.

[ohohyodafarted]

Originally Posted by miniman82

I had an idea on how to fix it, though I must admit I think more like a machinist than the electrician I really am. Sometimes that can be a good thing, though I have yet to lay hands on a 15GP22.

Seems to me the welded seal is the problem for many of the tubes, so why not get rid of it entirely? I mean, if there's a metal rim embedded into the glass, could you not just trim it back flush with the glass, then mate the 2 glass parts of the CRT together the same way neck glass is attached?

One other thing that I wonder about, is why if the metal part was leaking would you attempt to fix the leak by any other process but welding? I mean really, if 1954 welders could do the entire tube rim with a TIG torch, what's stopping those with rim leaks from sealing up a little pinhole? Is it really that difficult, or do tube people really not think that way RCA did back then?

To me, even difficult problems usually have very simple solutions...

And yes, you need to "lay your hands" on a 15G in order to appreciate the complexity of the issues involved. It has taken John and I more than 2 years of constant trial and error discoveries, to figure out where the problems are and how best to resolve them. It may look simple on the surface, but take my word for it, the issues are very complex indeed.

We will also have two 15G's on display at the ETF convention that were broken during our experiments. One tube has the entire glass rear section removed so you can get up close and personal with the shadow mask, and the other tube has the entire front cover glass and the decorative mask removed, so you can get up close and personal with the phosphor dot plate.

I am presently interviewing local welders to find someone with the talent to weld leaks that we have found in the Kovar TIG weld which fastens the two halves of the Kovar ultor flange. But only a small percentage of the 15G leaks occur at the weld line. Most leaks occur in the glass to Kovar bond or in two other Kovar to Kovar bonds, which I will explain in more detail in my presentation at the ETF convention.

Be there or Be square!

[miniman82]

Originally Posted by ohohyodafarted

We will also have two 15G's on display at the ETF convention that were broken during our experiments. One tube has the entire glass rear section removed so you can get up close and personal with the shadow mask, and the other tube has the entire front cover glass and the decorative mask removed, so you can get up close and personal with the phosphor dot plate.

I really do hope lots of up close pictures will be posted on the web, since I will not be able to make it. This is something I'd love to get involved in, since I'm good at solving complicated problems.