Rebuilding the 15gp22: A final report - Page 3 - Videokarma.org TV - Video

jr_tech · #31 03-15-2010, 03:54 PM

Quote:

Originally Posted by TubeType

Dear Jr,

It sounds like you have a viable process worked out. Currently, I'm not privy to the RACS frit seal protocol.
However, I'm sure Jerome will share his 15GP22 rebuild adventures at RACS during the ETF convention.

Kind regards,

My guess is that what I have outlined above would be a 1 in a million long shot... the most likely outcome of trying to get the 15GP22 apart and removing the flanges would be a heap of broken glass

If the folks at RACS *have* been able to do something like this... hats off to them! Next trick would be walking on water!

jr

TubeType · #32 03-15-2010, 06:38 PM

Quote:

Originally Posted by jr_tech

My guess is that what I have outlined above would be a 1 in a million long shot... the most likely outcome of trying to get the 15GP22 apart and removing the flanges would be a heap of broken glass

If the folks at RACS *have* been able to do something like this... hats off to them! Next trick would be walking on water!

jr

Dear Jr,

I'm sorry. I thought you were being serious.

Best wishes,

jr_tech · #33 03-15-2010, 06:48 PM

Quote:

Originally Posted by TubeType

Dear Jr,

I'm sorry. I thought you were being serious.

Best wishes,

Quite serious, but I think that it would take a great deal of skill and effort to do it... if indeed, RACS has been able to do something like this, they have REALLY pushed the envelope!

jr

TubeType · #34 03-15-2010, 07:07 PM

Quote:

Originally Posted by jr_tech

Quite serious, but I think that it would take a great deal of skill and effort to do it... if indeed, RACS has been able to do something like this, they have REALLY pushed the envelope!

jr

Dear Jr,

Until we see their results, all of this is of little or no practical value .

Kind regards,

AUdubon5425 · #35 03-15-2010, 08:31 PM

Dear Folks,

Why so formal?

Regards,

285425

ChrisW6ATV · #36 03-15-2010, 11:40 PM

Bob and John-

I am sad hearing of the end of your 15GP22 rebuild project, but the knowledge you have gained will be very valuable if further work is done in the future. Thank you for sharing the news of your latest tests and results.

jhalphen · #37 03-19-2010, 04:05 PM

Hi to All,

Well after 3 pages of glum news, we all need a "Booster Shot", including myself.

Here are 3 pictures of the ETF's 15GP22 after Frit-Glass resealing which took place early 2010.

In the meantime, both guns have been rebuilt, one by RACS, the other by Western. RACS routinely has some model guns rebuilt by Western, so this 2nd gun tagged along with a bunch of others sent to them.

They are now ready to do the rebuild attempt, most likely within the next 10 days. This was delayed because of an urgent batch of radar CRTs to be rebuilt ASAP while the French Navy boat was in dry dock.

Our goal is to ship a working tube early enough in April so that Steve's team has time to install it in time for the convention.

About the frit-glass process, i've had long conversations with them. They use an in-house process refined over years (starting in 1974), but i understood that there is much leeway in the mix of ingredients to cope with variable parameters such as tube size, amplitude of leaks, all glass or glass to metal seals, resistance to altitude ("flying CRTs"),...
This modifies the basic formula to target specific needs, essentially compromises between fluidity (filling cracks/metal fatigue cricks), thickness (filling large leaks, vacuum resistance and mechanical solidity), tube processing temperatures,...

The CRT is assessed for data prior to sealing, then modifications to the core frit-glass formula are determined by discussion between the Engineering Manager and the glass-working experts handling "the hot stuff".

As with all trades where years of human experience are everything, there is a grey zone between simply following the recipe and 30 years of experience of a glass worker where by instinct he will say: the mix is too fluid, thicken it, or some other simple-seeming comment which can make the difference between success or failure.

To sum it up, wish us luck, we only have ONE 15G until ETF convention time...

Best Regards, see you soon!

jhalphen

John Folsom · #38 03-19-2010, 04:13 PM

Jerome, we are keeping our fingers crossed! It would be wonderful to see a RACS rebuilt tube at the ETF!

old_tv_nut · #39 03-19-2010, 04:18 PM

Jerome, I know we are all hoping for the best! Could you explain a little more of what we are seeing in the pictures?

***Eric H*** · #40 03-19-2010, 05:36 PM

Does the sealing material have to be applied before the baking process?

If a tube was a very slow leaker why couldn't it be sealed after the tube cooled down?
After all it took months for the rebuilt tube to leak down and it's still not completely to air.

This would avoid the problems of differing expansion rates in the materials.

ohohyodafarted · #41 03-19-2010, 06:10 PM

First, I am also keeping my fingers crossed for RACS to be successful.

I don't know anything about frit glass, but I can tell you that our epoxy will seal vacuum leaks and it will also stand the temperature of 600 degrees F, for 6 hours in the evacuation oven without any degradation what so ever. It bonds to glass so well that the only way to remove it is to GRIND it off.

IN our experiments we found that a THICK layer of our high temp high vacuum epoxy became brittle and was subject to cracking. The tube will be flexing at the ultor ring when a vacuum is applied. We have since changed our epoxy protocol to painting a thin layer on the ultor ring in hopes that it will be more compliant to the flexing of the ultor ring when subjected to the vacuum.

To Eric:

Your assumption would be true for a dud 15G tube that is still under vacuum prior to the rebuilding process. We now believe that even an under vacuum 15G must be put through a sealing process prior to rebuild to prevent what happened to our first successfull rebuild. And yes, if we had even sealed the tube after we rebuilt it (which we did not think we needed to do) we would probably still have a working tube today.

However, for 15G that is full of air, it is unlikely that the leak would be small enough to give you enough time to seal the tube post evacuation. It would be a crap shoot at best. Sometimes it might work and other times it would be a total bust, if the leak rate was to big.

Presently working on the PowerPoint presentation for the ETF. So far I am up to 100 slides and counting. Better take some NO-DOZE, this one is going to be rather lengthy.

Bob

jhalphen · #42 03-19-2010, 06:37 PM

Hi Guys!

Bullet replies - tired & getting late here (half-past midnight)

John, Bob, Thank You! Nice & heart-warming good-luck wishes!

For Eric H;
Does the sealing material have to be applied before the baking process?
- Yes

If a tube was a very slow leaker why couldn't it be sealed after the tube cooled down?
- Frit Glass is a paste, it has to be baked at high-temp to become ceramic-hard and therefore vacuum-tight.

For Old_TV_Nut: Could you explain a little more of what we are seeing in the pictures?

You are seeing the rim of the ETF's 15G donor CRT re-sealed with Frit-Glass after leak detection. Really not spectacular, huh! just some beige ceramic-hard glass sealing up this heavy leaker (rust & metal-fatigue cricks under the microscope) - think 1952 De Havilland "Comet" 1st ever passenger jet midair explosions - same process in progress. Only time will tell after complete rebuild and IF it lasts if this was the successful formula.

Best Regards & signing off

jhalphen
Paris/France

rca2000 · #43 03-19-2010, 06:55 PM

I am not sure I understand all of this.

I am in no way knowledgeable about glass blowing and/or manufacture of CRT's...but SOMETHING seems amiss here with all of this. After all...at one time, not all that long ago...these 15GP/HP22 tubes WERE manufactured and /or rebuilt by RCA and others. Evidently, it was at least partially successful, as some of them still work, and at least often worked for at least 10 years or more after being built, before "giving up the (vacuum) ghost". And since they were made before...someone MUST still have the plans and/or machinery somewhere...or not???

So...what has happened to the 'original way of making these tubes"? Is it something like"there was only a couple of guys who knew how, and they took their secrets with them when they died long ago", or such??

Or...were these tubes GARBAGE from the beginning for RCA and did only one out of maybe 10 of them made actually work, for any length of time?

old_tv_nut · #44 03-19-2010, 08:56 PM

Quote:

Originally Posted by rca2000

I am not sure I understand all of this.

Not only did these tubes have different glass than later ones, they had an internal phosphor plate, so there was definitely a conflict between the temperature schedule for sealing and evacuation and protecting the plate from thermal damage. You also need to consider that the qualities of the glass change each time it is heated and cooled, so a schedule that works for original manufacture may not work for rebuild. I'm sure there are many other expert knowledge items that I don't know about, which disappeared when the last 15GP22 line was shut down.

ohohyodafarted · #45 03-19-2010, 09:15 PM

RCA 2000,

You ask many questions but here are a few answers.

First, the 15GP22 was never successfully rebuilt by anyone except RCA. Guns were not available. RCA had the only source. Anyone else that tried to rebuild this tube used a standard 21" roundie delta gun which did not provide for electrostatic convergence and was not a compatible rebuild.

RCA made the only production run of these tubes for general availability. Some other manufacturers "experimented" with limited experimental prototypes, but never put anything into production. As for the machinery and equipment that was used, I am sure it has all long been scrapped.

"Or...were these tubes GARBAGE from the beginning for RCA and did only one out of maybe 10 of them made actually work, for any length of time? "

The answer to your question is Yes, sort of. I will explain what I mean....

At the time these tubes were made, RCA was forging into new territory, and they were under a lot of pressure from the government in meating deadlines to demonstrate the viability of a "compatible all electronic" color tv system. In order to get the federal government to approve the RCA system over the CBS system, RCA had to demonstrate it's viability. So RCA was in a mad race to get something out to the public.

So they had to do whatever they could to produce a tri color crt in record time. As a result they drew on whatever methods and technology they had used in the past. There was no frit glass at the time so they could not make a two piece crt out of just glass. There was no way to join a two piece all glass crt. The 15G had be made in two pieces so you can install the shadow mask and phosphor dot plate inside. Photo deposition of phosphor dots had not been invented at the time the 15G was produced. That came the following year invented by CBS. And all glass color crt's did not come into existance until 1957 with the introduction of the 21CYP22 in the CTC7 series, when frit glass became available.

So the only way to join a two piece glass crt envelope together was to fuse the front and rear glass sections to a metal ring (bonding glass to metal was a perfected technology) and heli-arc the two metal rings together. There are more issues to deal with that I will explain in my presentation at the ETF.

But sufice it to say that the 15G was a "Rube Goldberg" style picture tube...IE: it was a complicated solution to a problem.

All you guys need to come the ETF convention and view the presentation. There will also be a number of touchy feely show and tell items that will be of interest.

See ya all there,

Bob