Re: 15GP22 Rebuild Attempt in France - Soon!

[ohohyodafarted]

OK... So long as the cat is out of the bag on this thread started by Jerome, I might as well put in my two cents.

First off, It is VERY HIGHLY likely that the leaks occur in the Ultor ring. John and I did the cross section cut away of the ultor ring that Jerome speaks of (we sent him photos).

The ring is composed of 2 glass to metal fusions (that you all are familiar with) and 4 layers of formed metal which are welded and fused together adding another 3 layers of joints around the entire circumference of the ultor ring.

In our cross section we could see that two of the metal to metal fusion joints are likely where the leaks occur.

IF the tube that RACS has in their possession was a leaker, it is not likely that the rebuild will succeed for very long. It will probably fill with air again. How long it will take is anyones guess.

John Folsom and I were ready to do a rebuild with Scotty at Hawkeye at the beginning of September. However Scotty injured his ankle in an athletic event and his foot is now in a cast. We are hoping that we will be able to make the first US attempt on a LEAK FREE dud that John owns, in the very near future (probably early November.) IF it works, then I will rebuild my LEAK FREE dud.

We appear to have the issue of cracking glass stems resolved with the design that John and I paid for and were manufactured for us by a US company out east. (This is the stem that Jerome mentions which John has sent to RACS in France) We sent the new stems to the Gun rebuilder and we now have 2 stems with rebuilt guns mounted and ready for the rebuild attempt. All we need is for Scotty to get better so he can perform the work for us.

After this attempt by John and I, we will then test out our leak sealing protocall which is top secret and proprietary. We believe it has a very good chance of sealing the leaks that are on the ultor ring, but only time will tell.

So that is where things stand on the US project that John and I are spearheading.

We will keep you all posted as to our progress as things develop.

Bob Galanter and John Folsom
The 15GP22 Project

[old_tv_nut]

Sorry to hear Scotty is in a cast, but also glad to hear he's still a part of this effort. And of course, if the super-secret sealant works on a 15G, I will be eager to have it tried on the 21AX that re-leaked on its first try.

[TubeType]

Originally Posted by jhalphen

Hi Guys,

John, Bob,

"We will then test out our leak sealing protocall which is top secret and proprietary. We believe it has a very good chance of sealing the leaks that are on the ultor ring, but only time will tell."

Not nice to not play ball, i've shared all info openly.

The common effort is to rebuild 15G's not become Maddoff-rich with proprietary secrets.

Good day

JH

Good evening Jerome,

I'm sure, when all is said and done, the "top secret" and "proprietary" protocall will be shown to be something quite "common" and "ordinary".

Bob & John, please tell us something about your top secret and proprietary protocall.

Kindest regards,

Terry Cheek

[ohohyodafarted]

WOW Jerome!!!

Don't get your nose all bent out of shape. John and I BOTH agreed to send RACS that stem that we developed and it didn't cost RACS a stinking dime.

We have thousands of dollars invested in the R&D of that stem alone.

You have no right to critisize us. The fact is, that John and I have spent MANY THOUSANDS of dollars of our own money, and hundreds of hours in R&D, and nobody has contributed a single red cent to our effort.

John and I will keep the formula for sealing the tubes proprietary if it is successful.

How the hell do you expect us to recover even a small part of our investment if we give our trade secrets away.

This is not only an attempt, by John and myself, to do something that has been needed by members of our hobby for many many years, but it is also a business venture.

John and I are not a multi-millionires with deep pockets. And our efforts are not for the purposes of charity. We need to be able to possibly recover our costs of R&D by offering this service to other collectors at a small profit for each tube rebuilt.

If and when our process proves successful, and we have recovered our costs of developement, John and I will, no doubt, be happy to donate the technique to the public.

Until that time, you will just have to be patient and accept the fact that John and I deserve a fair shake, and some gratitude for all the time and huge amount of money we have invested.

And just to emphasize a point here, I don't suppose that RACS will be willing to rebuild 15GP22's for free, Will They??? Oh yes and as I recall; weren't those glass ringlets that RACS developed to rebuild Pyrex tubes also proprietary? So I guess this is tit for tat. Eh? And if they weren't proprietary maybe you should have RACS send a handfull of those rings to Scotty at Hawkeye in repayment for the stem that John and I sent them for free.

"The common effort is to rebuild 15G's not become Maddoff-rich with proprietary secrets." ..... Comparing me to the likes of Bernie Madoff has to be just about the most insulting thing anyone has ever said to me.

"The Common effort" ...... sounds pretty socialistic to me and make no mistake about it, I am a free market capitalist. God bless America and the Red White and Blue!

Seriously Jerome you were WAY out of line with your comments!!! and have really pised me off with your attitude. So much so that I may never agree to divulge what we have developed. This kind of attitude reminds me of how the European Unoin constantly picks upon U.S. coporations who have intellectual property to license. I am thinking of Microsoft and Qualcomm just to name a few.

I could go on and on but what's the point?

And please understand that I am speaking for myself. John Folsom had no part of this post, and should not reflect upon him.

Bob Galanter

[Steve McVoy]

Please, everyone, lets stop this badmouthing. I'm happy that John and Bob are close to success with Hawkeye, and I'm also happy that RACS may also be close. Remember that neither has succeeded yet, and having two companies trying it increases the chance of success greatly. If it turns out that RACS needs John and Bob's sealing method, they will probably work out a royalty arrangement with them that will allow RACS to rebuild tubes and allow John and Bob to recoup some of their investment.

I appreciate the effort (and money) that John and Bob have put into this venture, and I also appreciate Jerome's effort in getting RACS to look at rebuilding the 15G, and also the prewar tubes that have so far been impossible to rebuild.

[John Folsom]

OK, let's all calm down. Take a deep breath.

We are not in competition with RACS, if they can rebuild 15Gs more cost effectively than Scotty (factoring in shipping costs in either case), then I will be the first one in line to sign up for their services, regardless of how much $$ Bob and I have poured down the rat-hole :-).

As for the leak detection, here is a sketch and photo of the cross section of the 15G flange seal. There are 2 glass to metal seals, and 3 (!) metal to metal welds, any one of which can be the source of the leak.

Bob and I speculate that the leak is most likely at the metal-to-metal welds which join the flat metal pieces together, though we have no science to back this up.

It is not obvious to me that the HV needle probe technique would work here. As John Yurkon points out, the metal in the flange would be at the HV potential and attempting to needle probe would not work.

As for the top secret leak sealing protocol, it is not a secret, I have discussed it with others, and the materials used are common knowledge in the industry. It may work, it may not (I am not quite as optimistic as Bob, for reason I will not go into here). Certianly RACS would be aware of our approach, and has likely rejected it for the same reasons that make me a bit dubious. But it is worth a try, I may be wrong (I often am!)

And frit glass is another approach, and at some point we may attempt this as well.

But for any sealing protocol to work, what we really need a way to locate the leak so it can be addressed directly. If the HV method can be made to work, that would be optimum. Helium leak detection is another possibility, but it requires expensive equipment, vacuum pumps and mass spectrometer.

BTW, I am sure some of you are thinking "VACSEAL!" After discussions with several people in industry working with ultra high vacuum systems, there seems to be a consistent opinion that VACSEAL will not be useful in this appplication, so we have abandoned thoughts of attempting to seal leakers using this product.

When Scotty recovers and starts rebuilding tubes again, Bob and I are ready to make another attempt using a non-leaker tube and our new and improved stems.

Good luck to us all!

[Sandy G]

Yeah, come on, guys, snipin' amongst ourselves isn't productive at all. We're all supposed to be friends here...That's one of the things I like most about the old TV/Radio fraternity.

[Eric H]

Well John, after seeing that diagram and cross section I gotta say it's a miracle there are any working 15G's at all.
So many potential trouble spots.

What was the purpose of the double wall of thin metal?

It looks like possibly it was to allow for different expansion rates between the bell and the face plate, is the corrugated washer welded to anything or just squeezed between the two pieces to provide some tension?

Would it be possible to pressurize the tube slightly with an inert gas and simply look for leaks with soapy water like you would a tire? I suppose it would have to be a pretty large leak to find it that way, also I don't imagine you could put much pressure inside without exploding the thing.

[John Folsom]

Eric,

I think you are right, the complex joint was made to allow for thermal expansion. Too bad they did not have frit glass.

I suspect most of the leaks we are looking for are microscopic in dimension, and would not produce any bubbles.

The corrugated washer isnot aattached, it is simply pinched between the 2 flat faces. Here is another photo highlighting the washer

[ohohyodafarted]

Hi Eric,

The entire design of this tube and in particular the Ultor Ring Assembly, is predicated on a number of design constraints.

I will attempt to take the issues one at a time.

First RCA needed a method of making the envelope in two pieces. A front half and a rear half, so as to facilitate the instalation of a third assembly inside the tube. That third assembly is the phosphor dot plate/shadow mask assembly.

The technique of fusing glass to metal was well understood. So it was decided to make a glass front face assembly fused to a metal ring, and a rear glass funnel and neck assembly fused to a metal ring. Then the phosphor dot plate/shadow mask assembly would be mounted to the flange on the rear assembly, and the front half and rear half would be brought together and the two ultor ring halves would be heilarced together to form a complete crt assembly.

The phosphor dot plate/shadow mask assembly mounts to the light guage rear half of the ultor ring inner flange assembly with 3 bolts.

The reason for the two light guage metal rings with the bulge on the outer circumference, is that when the tube is evacuated, great amounts of mechanical force are exerted which squeeze the front and rear halves of the tube together exerting great amounts of pressure on the two light guage metal rings. The rings need to flex under the pressure. The pressure needs to be distributed evenly around the entire surface where the two halves of the ultor ring meet.

The corrugated metal washer that is sandwiched between the front and rear rings, is designed to act as a cushion to evenly distribute the tons of force squeezing the two rings together. If the corrugated washer was not there, the front and rear metal rings would squeeze together, and in the places where the rings would touch all of the force would be exerted in just those spots. That would cause huge stresses and probable breakage of the glass to metal bond on the front and rear rings. Even if the glass to metal joints survived, there would be pressure points that would make the tube vulnerable to implosion if bumped or jared.

The reason for the heavy metal rings which are the bonding surface for the glass is thought to be as follows. The light guage metal would likely melt under the high temperatures needed to fuse glass to metal. To solve this problem, heavy guage metal rings were bonded to the light guage sheet metal rings. Probably a rolling fusion weld under great force and very high current. This is the joint which probably leaks.

I had long suspected that the leaks were occuring in the metal to metal fusion jonts between the heaavy and light guage metal rings. So when John was in Milwaukee a couple months ago we decided to cut a cross section of an ultor ring that we had been using to experiment on. We used a 3 inch high speed carborundum disc to slice a section of the ultor ring away. We then ground and polished the cross section to a high finish so we could closely examine the integrity of metal to metal joint.

AS you can see from the cross section photo of the ultor ring in John's post, the heavy guage ring is not bonded uniformly to the light guage sheet metal ring. There is a very evident partial gap between the two components. This was only a random cross section and we found deficiencies in the metal to metal joint. I strongly suspect that some areas are joined better and some are joined much more poorly.

It is this metal to metal fusion weld between of the heavy guage ring and the sheet metal ring that will need to be sealed. We can't be sure, but we do not think the glass to metal bond is where the leaks occur.

Glass to metal bonds were well perfected and being used in metal funnel crt's for many years before the 15GP22 was put into production.

There has been much discussion betewen John and myself about the usability of frit glass to try sealing the metal to metal fusion joint. And John and I have differing opinions on the use of frit glass to seal 15GP22 leaks.

I had a very long and interesting discussion with one of the elderly engineers who worked at Rauland picture tube. I also spoke to a fellow that works for one of the companies that make frit glass. These fellows both told me that frit glass will not work for the metal to metal leak we are trying to fix. The problem is that the coefficient of expansion of the frit glass has to be matched to the metal very precisely. And even if we were able to match the expansion coefficients properly, due to the fact that the sheet metal ultor ring flexes when the the tube is evacuated, the frit glass would crack due to the flexing.

Frit glass is very useful to bond two glass surfaces of a crt together because the glass all moves at the same rate. When you get dissimilar rates of expansion or physical stresses such as the ultor ring flexing, then frit glass will fail. It will either crack or debond from the surface. Even in glass to glass joints, if the frit glass in not perfectly matched to the rate of expansion of the glass parts, the joint will fail.

As to your query on leak detection, as was discussed in another post the spark method is not going to work on the metal ring as it is electrically conductive throughout. As to pressurizing, you are correct the leak is too small to find this way and may explode the tube because it is not designed to be pressureized, it is designed to be under vacuum.

The only practical method of leak detection would be with a helium leak detector. IN this method a strong vacuum is pulled on the crt by a machine that is designed to count Helium atoms in the vacuum stream. Helium is used because the atom is so small it can squeeze through the smallest of leaks. So while the tube is under vacuum via the HE leak detector, the operator introduces small amounts of HE from a tiny supply tube into the areas where the leak is suspected. Almost instantily the HE leak detector will detect the HE atoms in the vacuum stream and a meter on the machine will register a large number of atoms. As soon as the meter registers, you know you have found the leak.

All this leak detecting is in my opinion not of much use. Even if were to find the exact pont of the leak, and seal it, additional leaks could crop up in other spots. The solution is to seal the entire metal to metal joint all around the tube to make sure that the leak is fixed and to prevent any possibility of future leaks occuring.

I hope this has shed some light on the subject of why the tube was built the way it was and where we suspect the leaks are.

Bob

[John Marinello]

Forget about pressurizing ANY crt for ANY reason. Glass is excellent under compression, but should NEVER be subjected to tension. A few pounds into a 15GP22 would cause the ultor flange to act as a bellows, thus ruining that. Add few more pounds, and the tube will explode & cut you to ribbons.

[jeyurkon]

The corrugated crush washer appears to be a different metal than the other parts in the photograph. Is it aluminum by any chance?

John

[TubeType]

Thanks Bob and John.

It was nice to read your detailed explanations of the 15G's construction. I counted five glass-metal or metal-metal junctions. That's ten bound surfaces. This is a mechanical engineer's nightmare.

Have you considered using a large molten glass band to completely encompasses the Ultor ring? This glass band would be fused to front and rear glass surfaces of the 15G. It would include a feed-through connection to the Ultor. If this technique is mechanically sound, wouldn't it eliminate most if not all of the sources for vacuum leaks?

Kind regards,

Terry Cheek

[jr_tech]

Thanks Bob and John for posting the construction details of the 15gp22. Wow! No wonder many of these crts leak. I suspect that percentage wise, more prototype metal cone 15" crts have survived!

I suspect that patching over the outside of the seal areas with frit (or glass) would not be a permanent solution. as flexing of the seal area is likely to fracture these brittle materials. Also, I suspect that pockets of air that could be trapped between the frit and the metal flange could be a source of a "virtual leak" that could over time cause the tube to become gassy even though there may be no detectable path to the outside...

Tough problem !

jr

[ohohyodafarted]

jeyurkon:

The crush washer is of a different metal. I dont have it hear, but it is either aluminum or Stainless steel.



jr_tech:

Your asumptions are right on. We too are concerned about redidual gas entrapment after sealing the metal joints. Hopefully the amount of entraped air would be so minimal as to be absorbed by getter material.

I have a 16gp4 that has milky getters. Presumably from a leak. But it still produces a very good picture. So, it is possible that if the getter flashes are very large, we may be able to counteract the infiltration of any small amounts of gas that might get entraped in the ultor ring after it has been sealed.

Bob