If you are using rebuilt 15GP22 guns, which can't be cheap to rebuild, Don't waste them on tubes that are known leakers. Concentrate on rebuilding tubes that are under vacuum for now, maximize your success rate, improve the process, and worry about the duds that have gone to air later. I'm not sure a tube that has a leaky flange seal can ever be repaired and rebuilt satisfactorily.

Just my thoughts.

I would guess that perhaps most of the 15GP22s that need rebuilding are, in fact leakers. :(

jr

---

__________________________________________________ _________

UPDATE 10/26 5pm

I just spoke to Scotty. The news is somewhat mixed. The good news is that the rebuilding of the guns with new cathodes appears to be very good. Emission is right up there where it should be. Equal to any standard delta gun used in conventional 21" roundie color tubes. A bit slow to warm up at this point but Scotty thinks that it may "wake up" as we use it.

However we did have one slight setback. Un-beknownst to us, the getters were too close to the inside of the neck glass. And when Scotty hit the getters with the RF bomber, the heat of the red hot getters caused bubbling of the neck glass. The tube is holding vacuum, but there is a chance that when the neck heats up from prolonged use, the heating of the glass from the filiments could cause the neck glass to crack and we would lose vacuum. If that should happen, the tube would not implode, it would just go to air and we would have to rebuild it all over again. This problem is easily correctable by adjusting the position of the getter rings on the gun so they are farther away from the inside wall of the neck glass. This will be done starting with the next rebuild.

I have instructed Scotty to put the tube on his test bench and apply 6.3 volts and let it run for several day non-stop to see if the neck glass will hold. There is no point in shipping the tube to John's house only to find out that when we run the tube for a prolonged period, and the neck glass gets good and hot, that it cracks. Scotty said that he has seen this go both ways. Sometimes the bubbles will cause the neck to crack, and sometimes it will hold. Really no way to tell without giving it a good heating.

But at least we know that the guns have what appears to be excellent emmission.

I will post more information as things develop

Bob Galanter and John Folsom
The 15GP22 Project

Amazing! Congratulations guys! I really hope that the bubble in the glass holds. Fingers are crossed, again. :D

Really do hope after all that work it's a good 'un, fingers most definitely crossed! However if trying to root out whether there is a possibility of a failure, wouldn't it be better to cycle the heaters as simply running the tube continuously won't necessarily put the kind of stress on the tube that it'd get in real use.

TTFN,
Jon

Good point. I will speak to Scotty and suggest that he run a cycle of heat up and cool down to stress the glass more like real world condions.

Thank you for the suggestion.

Bob

With the bubbles, could the yoke and convergence components even be installed OK?

The bubbles are very tiny and on the inside of the neck glass. there will be no problem with anything that needs to be mounted on the neck.

Scotty is cycling the tube off and on. 2 hours on and 2 hour off as Duke Nukem suggested. So far so good.

Bob

Tom,
An expansion on what Pete said about having the guns rebuilt: After the gun is removed, Bob Galanter uses an EDM (electro-dynamic machining) tool to mill out the old cathodes from the gun structure with micron precision. Bob built a custom jig to hold the gun assembly which allows the precision EDM machining to be done. Without Bob's expertise, the 15G project whold have come to a halt becausee the company which puts new cathodes and filaments back in ghe gun and mounts the gun on the new stem was no longer willing to attempt the difficult task of removing the old cathodes. I do not think they had access to EDM machining.

Tune in next week for final acceptance test results on the CRT rebuilt at Hawkeye.

"Tune in next week..." That's like forever! At least when you're waiting for something exciting like this.

John

Hello Gentlemen,

While-U-Wait for more news on Bob's/John's 15G, why not read a bit?

I've scanned for you 4 interesting Color TV-related articles from the RCA Lancaster factory magazine:

- Milestones in color picture tube development - H.R.Seelen
- Development of cathodoluminescent phosphors - A.L.Smith
- Gasses & Getters in color picture tubes - Turnbull/Moscony/Month/Hale
- Colorimetry & contrast performance of color picture tubes - Ehemann/Rudy

RCA Lancaster: Main Directory
http://s281.photobucket.com/albums/k...ancaster%2069/

For those in a hurry, the link to the Gasses & Getters article (4 pages):
http://s281.photobucket.com/albums/k...tersinColo.jpg

Best Regards

jhalphen
Paris/France

Interesting Read Jerome, Thank you!

Update: The 15GP22 from Scotty has arrived at my house. :banana: No damage, all appears well. The tube has not been based yet. Bob Galanter will arrive tomorrow, so I am waiting so he does not miss any of the fun!

"one small step for a man ... "
 

MAY GOD SPEED, JOHN FOLSOM.

Regards,
Terry Cheek