Question about 15GP22 production
 

Does anyone have concrete information as to when exactly commercial production of the 15GP22 began, and when it ended?

I know the developmental tubes in the Model 5s were built starting in November of 1953. I'm assuming commercial production of the 15GP22 started in late December 1953 or early January of 1954, and probably lasted maybe six-ish months at most? And about when was hand welding of the ultor flange abandon in favour of automated welding?

My good 15GP22 was manufactured the 13th week of 1954; I'm trying to determine if this tube was hand or machine welded.

Answer: both, not that it matters.

Even a ‘machine’ weld in those days was still a manually controlled TIG weld, and any holes found by the leak detector would have to be fixed by hand.

Thanks Nick. Bob mentioned to me that the later 15Gs seem to have a lower leak rate in his opinion.

Does anyone know when production started and stopped? I'm more interested in knowing how long the tube was actually built.

My 1964 Allied still listed a 15GP22 for $222.00. IDK, if it was NOS or recently manufactured.
The newest type listed was a 21FBP22. :scratch2:

Ben, the oldest 15GP22 I know of has a date code for the fourth week of 1954.

Pete

That's a bit younger than I was expecting. Thanks Pete.

It kind of pokes a hole in the hypothesis that the Admiral set was the first commercially available color set: Admiral would not have been selling sets with prototype jugs to the public, and if the oldest known production 15GP22 is from the fourth week of 1954, then nobody could have commercially released a set before then. You've gotta have CRTs to put in 'em...

Maybe this is the back-end of the puzzle. Link to the graphic on my site of the only 15GP22 date code I know of that is not from 1954; it is from 1959 (in case the link doesn't work).

http://www.earlytelevision.org/Deksn...926-15GP22.jpg

Pete

Makes one wonder if it was a rebuild, or if the 15GP22 was still being manufactured new?

I figure RCA had built four or five thousand CT-100s, then there were the other 15 inchers (at least 500 Westinghouse sets, 100-200 GEs, etc) and finally all the studio monitors. There would have been some demand for 15GP22s into at least the 1960s. Probably not that great of one, but a real demand nonetheless.

My feeling always was that it was new. Or, perhaps assembled from a pile of parts held in storage for years...?

I think there are two plausible explanations:

The datecode is a misprint and it should be 1954, or the tube was manufactured new in 1959. The 15GP22 is on price sheets well into the late 1960s and early 1970s. Warehousing a bunch of product is expensive. It's possible that RCA kepts parts around to "build" new 15GP22s on demand for a while. They wouldn't be the first company to do something like that...

If it was a rebuild you'd expect to see a label saying that the envelope was reused and the tube was rebuild. I've seen an RCA rebuilt 15G with such a label, and I've never seen a rebuilt tube without a label clearly identifying it as such.

I think your gut feeling is right Pete.

i suspect they may have kept in production a while for studio montor use.. since 21" tubes might be a little big for that purpose. Were there any other smaller tubes available for when a 21" might be too bulky?

Just my opinion. The whole 15GP22 production was so crude with the flat plate, early phosphoring, physical alignment, welds, glass to metal, etc., It had to be low production and the 21 series blew that out of the water to the bean counters. I cannot imagine RCA kept that assembly line around for long. As for studio monitors it was a quick jump to jeeped up 21CT55 sets as many photos document. I think the ones on Allied, etc. were happily gassing away in loneliness on the shelves.

On application of the 15G that lasted a LONG time was color film viewing machines (I forget the correct name) used for doing color correction/editing of films.

I remember a page on one of the big CT-100 sites many years ago told of how a few years before a collector contacted the company that maintained these machines, the company had given up servicing the 15G equipped machines and tossed 6 NOS 15Gs in the dumpster.

(1) the last machine using a 15GP22 operated until around 1975 in Mexico.
(2) Your remembrance is on my CT-100 site; here's my painful posting: What's the chance that serendipity will rescue a pallet of 15GP22s from a dusty warehouse somewhere? I've always believed it would. This next email shows it can happen and hopefully will.

"Date: Sat, 03 Nov 2001 14:16:55 -0800
Pete,
I am sick. I had no idea that anyone was interested in these old tubes.
I make color film analyzers and had the old stock from Hazeltine when
they discontinued production. There were six of those old 15 inch CRT's,
but since there were no more analyzers in the world using the tubes, we
chucked them to make room.
Regards,
Ric "

(6 Nov 01 update: Just missed these by a couple of years! The six 15GP22's had their vacuum broken, then were sent to a Los Angeles landfill sometime in 1997 in their original RCA cartons. We'll keep looking for a pallet with the next batch of 15G's.)

Thanks, Pete!

RCA, as would any legitimate builder/rebuilder, would have labeled the crt as rebuilt in some way. I don't know when they started using the "Grade A", "Grade B" etc system. At least it would mention used envelope, new gun, etc.

Were the date code on a paper label I would speculate the date would indicate when it was packaged, but with it on the socket I think it more accurate. I have seen tubes with 2 dates on them (all the tubes in one of my Portacolors were like this.)

Dave I believe you are right on the money about the length of time RCA would have kept the 15G production line.

It is my belief that RCA probably manufactured a certain amount of surplus for replacement tube warehouse inventory. In addition, tubes that were in the field and replaced due to low emission, which were still holding good vacuum, could have been a source of candidates for re-gunning at RCA after the original production inventory run had been depleted. I believe someone posted that they actually had seen a 15G with a sticker that stated it was a rebuilt tube. So that confirms that RCA actually did rebuild some 15G's.

One of my 15GP22's has a 1959 date code.

https://farm5.staticflickr.com/4651/...292736e2_z.jpg

John, I think this makes your tube the latest known 15GP22, as the other 1959 tube that Pete references above is from week 26.

It's also interesting that this is now the 2nd '59 tube to show up and that no other tubes between '54 and '59 have surfaced to my knowledge. Unless this is purely coincidental, this makes it more plausible in my mind that Lancaster did a second run of these in '59 to replenish replacement stock. However, one would think they would have done so over a very quick timeframe (like a week or two), not 13 weeks. Or maybe they were intermittently reworking '54 tubes that had already gone to air while sitting in RCA stock? (However, I don't recall your tube showing signs of re-necking).

Are there only two known 15GP22's not from 1954?

RCA rebuilding 15G's?
 

After acquiring CT-100 B8000173 in 1963, I considered buying a spare 15GP22. At a suburban Philadelphia supplier I checked, they were available, but the purchase-price required a dud be returned.

Pete

Why would they have wanted a dud if they weren't rebuilding them in 1963?

If RCA could rebuild them then, why can't we do it now?

Because only a crt that is holding a PERFECT vacuum (not a leaker) can be rebuilt. The duds that are in the hands of collectors are leakers that will not hold a good vacuum after rebuilding. Rebuilding a leaker is a waste of time. It will only produce a picture for 30 days or less, and when the vacuum degrades, the crt will once again be useless.

A method of fixing the leaks must be found before a successful rebuild will be possible.

Bob, this is where I always get a little confused. If it's true that ANY tube found today that has now gone to air will "only work for 30 days or less" after rebuilding (which I have to believe, since you've been studying these things for years), that must also affirm that ANY such tube only began leaking after some finite event along its lifetime (failed weld, failed glass to metal bond, stress crack in the glass, etc.). For whatever reason, I can't get it out of my head that at least SOME of the tubes found today that have gone to air did so at an even rate from the very moment they were made, and only at some point along their lifetime (twenty years ago, two years ago, or two minutes ago) enough air entered to finally consume all of the getter material and cause the filament to fail. If it took ten or twenty years for that to happen, then why couldn't it be assumed (unless the leak were made worse during the rebuilding process) that the rebuild would not last equally long? Not doubting you here - just wanting to understand why that's not possible or even likely for some tubes.

Bob's the expert, but I believe part of the problem is that the stresses change irreversibly when the tube is processed the first time, and subsequent cycles just make things worse.

I fully agree - to the point that I wouldn't lay any money that a tube with "perfect" vacuum prior to rebuilding doesn't stand a substantial risk of becoming a leaker afterwards. People talk about using vacseal, not subjecting a good tube to temperature or humidity changes in situ, etc. Yet, these stresses pale in comparison to the beating these weak points will need to survive during a successful rebuild process.

WRT: the tubes still under vacuum; We have rebuilt tubes that were under vacuum, and they developed a leak big enough to spoil the vacuum withing 30 days. Another builder out in California tried the same thing many years ago and ended up with the same result. They will go to air in about 30 days.

Tubes that have lost vacuum are even more problematic. It does not matter if the tube was good for 50 years and then suddenly sprang a leak, or it leaked very slowly for 50 years to the point where it had to much air in it. The fact is that it has a leak. A leak is a leak and even if it is a slow leak when you put it in the oven to evacuate, the heat and stresses of pulling a vacuum will make the leak even worse.

At some point down the road perhaps we might be able to seal the tubes with a special epoxy that we have experimented with in the past. The issue is that we will need to do a very long low temperature pump down so that the special epoxy does not burn up. But to do that we will need a facility that can do the experimental work. When Hawkeye closed it's doors several years ago, we lost our last good rebuilding facility where we could go and conduct experiments.

Until we have a facility with good equipment in which we can conduct experiments, we are going to be at a standstill with the 15G project.

I wonder if it would be possible to complete all the steps of evacuation short of pinching off the evacuation tube then connect a helium leak detector and inspect the tube/try to correct new leaks before the final pinch off?

Tom,
Even if no leaks were found, When you finally put the tube under vacuum and heat, this is the point where the leaks are created. The heat and physical vacuum stress, causes weak areas (usually in the glass) where micro cracks form at the juncture of the glass and the ultor ring.

It is an easy matter to find out if the envelope is leak free before evacuating. The leaks are created during the evacuation process. Even if you could test for a leak during evacuation during pump down, prior to pinch off, What good would it do? You could shut down, but you still have a new gun installed in a envelope that has a leak. I guess you might be able to salvage the gun and stem assembly by cutting it of and possibly re-using it on another tube. But we are better off finding a method of reliably sealing the envelope. Without a method of reliably sealing the envelope so that it doesn't leak during evacuation, attempting rebuilds of 15G's is pointless and we are just crossing our fingers that maybe 1 in 10 attempts might yield a good tube.

The one tube that RACS was successful with was a tube that did not have any leaks to begin with. It was pure luck that It did not develop any new leaks during the evacuation. It was just pure dumb luck. But it does demonstrate that it can be done under the right circumstances. RCA was rebuilding duds that were not leakers.

That's why we are hoping that a long, slow, low temperature pump down, combined with a special high temp epoxy that we have worked with, may help to lessen the possibility of causing new leaks in an envelope that is leak free prior to evacuation. It may even be able to seal micro fractures that exist in tubes that have a slow leak.

The epoxy would be applied in a manner similar to what RACS did with frit glass in France. However their attempts to seal with the frit were utter failures. IMHO frit was not the correct approach. Frit is designed to be placed between 2 precission ground glass surfaces. RACS thought it might work by slathering it on the outside of the tube. Frit was never meant to be used that way.

And there is no assurance that we would have any better luck with a low temp pump down and the special high temp epoxy. We will never know unless we are able to do some more experiments. Perhaps some day when Nick gets his crt rebuilding facility up and running.

As for me, until I am free of the responsibility of caring for my 102 year old mother, I rarely have any time for pursuing my hobby. I have care giving responsibilities 7 days/week, 365 days/year.

Bob, I remember a while back that someone was attempting to do an all-glass version of the 15GP22, thus eliminating the troublesome, leaky ultor ring. Do you (or anyone else) know the status of this project?

Progress is slow, it is still a work in progress. It still has to have the gun installed and be evacuated. It currently holds a good vacuum under test conditions.

This is what you're remembering.
http://www.earlytelevision.org/yurkon_15g_project.html

I think John's approach is likely to yield a good tube for him, but I doubt very much it could be repeated with any degree of success say three or four dozen times.

I hope the Epotec solution works, but I'm not holding my breath. There have been how many attempts to rebuild 15GP22s? And one successful tube (the 15GP22 in the ETF's Sparton) that appears to be little more than dumb luck.

Is it technically possible to rebuilt a 15GP22? Undoubtedly. Can a suitable solution be found to the problem, that is fairly trivial to repeat on dozens of tubes, and at a cost that a collector with a dud 15GP22 would be willing or able to pay? Maybe, maybe not. My gut says no.

My advice for anyone with a working 15G is twofold: treat it with kid gloves, and use the damn thing! I would rather get a solid year or two of enjoyment from the 15GP22 in my Westy, than turn the set on one day to find a bright pink neck and wish I had watched it more. That's why I'm having Nick do the restoration. It'll be done faster than I'd ever be able to complete it, and I'll be able to enjoy the set some.

I have a 1965 Allied catalog that does NOT list a 15GP22 in its CRT pages. That might be one indication of when new or rebuilt 15G's stopped becoming available.

I DID watch my 15GP22 (above) until it died by arcing. I watched NFL
and the World Champion Chicago Cubs games on it.

OF course they can be made to work again, as long as we can get
guns. At worst, due to the way the front end is made, the metal parts
could be installed in a completely new glass envelope. The problem
is getting alignment good enough for ok convergence.

The price I'll pay .... I'll give no number, but note that I own a TT5 and a Marconi 702.

I'm still considering replacing it, at least temporarily, by a rectangular Trinitron tube
that does not need convergence, and a fake external mask. I will try talking to people
about that at the ETF. If I ever succeed, it would make a great ETF talk. The problem of course
is horizontal drive ... maybe use the transistorized board of the donor set?

My comment about watching the set while the tube is good didn't apply to you Doug. You seemed to be playing your CT-100 very often, at least from what you posted on VK. That's the way it ought to be. Use it before you loose it...

I was referring to a collector that I know, who shall go nameless, who watches his restored CT-100 once, or at most twice a year, in order to "save the cathode material". You can have the best cathodes in the world, but if the tube is gassy, it doesn't matter.

All I know is that I am utterly fascinated by the CRT restoration efforts whether directed to 15G's or other tubes. The revisiting of the original RCA docs to understand the material science involved is epic.

The re-creation of the original or improved materials in this day of everything being labelled a carcinogen, and blocked from access to the general public or even technical workers, goes way beyond anything I've ever seen.

Special jigs and fixtures built from scratch with great attention to detail is an art form, as is the entire process. No doubt about it.

I live in the Seattle area where a certain Mr. Chihuly lives are creates fantastic glass sculptures. Many buildings in the area are endowed with his work. This effort is no less significant than that.

To all of you, RESPECT!!!

Couldn't agree more!