Re: 15GP22 Rebuild Attempt in France - Soon!

[jr_tech]

The best of luck on this rebuild! I have a dead one also Has anybody accomplished a successful rebuild of a 15GP22 ?

jr

[Steve McVoy]

Originally Posted by jr_tech

The best of luck on this rebuild! I have a dead one also Has anybody accomplished a successful rebuild of a 15GP22 ?

jr

I have seen 15Gs that have been rebuilt with 21 inch guns. Apparently convergence assemblies from 21 inch round sets were installed, and only the static convergence magnets were used. Because the screens are so small, they probably looked Ok without dynamic convergence.

It is possible that 15Gs were rebuilt with 15G guns in the early days, but I have never seen one.

As for recent attempts, John Folsom and Bob Galanter have been working with Scotty at Hawkeye in an attempt to rebuild a tube. They are close, but no success so far.

[jeyurkon]

That's great progress and it's wonderful that they are taking on this project!

I'm embarrassed to say that I forgot about this leak testing technique even though I own a specialized HV probe used by glass blowers to search for leaks.

However, if the leak is at the ultor flange as Bob and John think, then I doubt that this technique will work because the metal is an equipotential surface. You wouldn't be able to pinpoint the leak. Also, since the flange penetrates the glass it would conduct even better than a pin hole in the glass.

Unless I'm overlooking something.

John

[andy]

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[jr_tech]

Originally Posted by jeyurkon

However, if the leak is at the ultor flange as Bob and John think, then I doubt that this technique will work because the metal is an equipotential surface. You wouldn't be able to pinpoint the leak. Also, since the flange penetrates the glass it would conduct even better than a pin hole in the glass.

Unless I'm overlooking something.

John

I think that is quite correct... and also suspect that the flange weld or the flange-to-glass seals are very likely leak areas. Perhaps a coating of Vacseal over the entire flange area would be helpful?

jr

[jhalphen]

Hi Guys,

John Yurkon, Thanks! for this input:
However, if the leak is at the ultor flange as Bob and John think, then I doubt that this technique will work because the metal is an equipotential surface. You wouldn't be able to pinpoint the leak. Also, since the flange penetrates the glass it would conduct even better than a pin hole in the glass.

Will translate ASAP & send to RACS, it's good forward thinking.

I did send them in August the set of Flange Cross-Section photos taken by John and Bob.

To everyone: Thanks for the encouragement.

A useful thing we can do right now: find some really "Lean and Mean" pricing quotes on USA to Europe shipping for a box containing a CRT the size of a 15G. We already got hit in the teeth with atrocious prices (US $1200.00 each way) for prospective DuMont 30 inch CRTs, as a result, none were sent.

Best Regards

jhalphen
Paris/France

[kx250rider]

Originally Posted by jr_tech

Has anybody accomplished a successful rebuild of a 15GP22 ?

jr

Not for long. I had one re-evacuated by the owner of a tube rebuilding shop in SoCal in the early 80s, and it worked fine for about 6 months, then began to glow purple in the neck and arc internally. It was a leak around the anode ring, I'm sure. The trick was, at the time, to heat it up over a couple days, rather than the several hours they usually used. The owner of the shop was a retired engineer from Hoffman, and he had worked on a project there to build a proprietary tube for Hoffman color TVs so they wouldn't have to use an RCA or a CBS tube; both of which they tried in prototype sets. He also did the only true successful rebuild on an 8" Arvin metal tube for me, as well as several 21AXP22s for myself and others. He sold his equipment to a CRT rebuilder in Mexico and retired in the 80s, and I lost track of him. (Ron Richardson, Dunbar Picture Tube Company. Culver City, CA). If he's still with us, he'd have to be about 90 by now, I guess.

Charles