[jeyurkon]

In case I haven't already convinced everyone that I don't live in the real world these ideas probably will fix that.

It seems to me that metal ring that causes leaks in the 15GP22 actually might make it one of the easier color CRTs to attempt to re-phosphor. No doubt someone has probably already thought of this and why it won't work, but since I'm a newbie I want to bounce these ideas off of the forum.

Assuming that Bill Gates wanted a 15GP22 re-screened and said that money is no object, the procedure would go something like this:

Bring the CRT up to air, or verify that it is up to air.

Remove the weld on the metal ring. Machining or abrasive techniques would be a bit risky so the safest way would be to EDM the weld. We don't care about the electrolyte getting into the CRT since we're rebuilding it.

After separating the bell from the faceplate remove the decorative mask, phosphor-dot-plate and shadow mask.

Remove the gun from the bell. Clean the faceplate and bell removing all of the dag. Now would be the time to repair any problems with the glass-frit.

Clean the phosphor-dot-plate removing all of the phosphor.

Now we need some fixturing to accomplish the following. We also need some supplies and decide what type of phosphors to use. I had to purchase some CRT Red Phosphor for work. It was Nichia NP-1154 Y2O2S:Eu. The minimum was 1kg at a cost of $1.5K. You might want Phophors to match the original emission spectra though.

The first phosphor is mixed with a photosensitive polymer and appropriate binding agent. It is placed onto the phosphor dot-screen and spun to evenly distribute. After drying, the shadow-mask is assembled with screen. A UV point light source is positioned in the same position as the appropriate gun for the particular phosphor and the polymer is exposed. This hardens it. The screen is then washed and only the polymer and phosphor that was exposed remains. The original method involved a separate silk screen exposure but this method is more precise.

The screen is then baked. The process is repeated for the remaining two phosphors.

At this point you might want to apply a black coating to surround all the dots, but after getting this far I don't think it's worth the risk.

Now a lacquer is applied. Then the dot-screen is placed in an evaporator and a layer of aluminum is evaporated on to it. I would bake the screen again, probably in vacuum or inert gas to remove the lacquer at this stage. It would be easier to fix now if there is a problem rather than after the crt has been reassembled.

The decorative mask, dot-screen and shadow mask are now assembled with the faceplate.

In the meantime the bell has had aquadag reapplied to the inside.

The bell and faceplate are reassembled in the proper orientation. Then the metal rings are TIG welded again. This is a critical operation but can be done by hand by an experience welder. If it's done improperly the frit-glass may crack and leak.

I would then helium leak test the assembly and repair any leaks. A coating of solder-glass or frit glass painted on to the glass metal transitions would be a safety measure and then fused at the appropriate time.

The new or rebuilt gun would be added now and the CRT processed following normal re-gunning procedures.

Enough of my crazy ideas. But they're here for you to shoot holes in them.

I was amazed at how much information is available on the web for the 15GP22

John