CRT Rebuilding update
 

There have been some recent developments regarding the rebuilding effort, so I think an update is in order.

You all know by now that a successful rebuild attempt was made during last years ETF convention: I completed a 17CP4 metal cone tube that is still holding vacuum today, which proved the basic operation of the equipment at the museum. That tube mistakenly had a gun with a 12v filament installed in it, we still don't know how that happened but at least the tube works. In the future it will be easy to check the heater of the guns before installing them, to make sure that doesn't happen again.

Recently I made a trip to LA to purchase a large inventory of tubes and rebuilding equipment from a company called Quest International. They are still in business, just not with tubes anymore. The tube inventory is being sold on the ETF site, so if you need anything in the way of B&W or color in a square glass format contact the museum. They have a part number list of what I brought back with me, and we're working on getting technical data on them. These were used in medical imaging, high res stuff.

The rebuilding equipment was brought back to my place here in Southern Maryland, for two very good reasons:

1. I can't be at the museum full time rebuilding tubes, and only 2 weeks a year during convention time rebuilding tubes helps no one. We would only get 1, maybe 2 tubes like that.

2. I'll have complete quality control over every step of the rebuilding process here at home, it will be my retirement job. I'll also be customizing the equipment to suit my needs, which should help increase output as much as possible.


This doesn't mean the stuff at the museum goes to waste, I'll still be there at the meet demonstrating the equipment and it's still perfectly viable machinery if someone wants to learn on it. I made the decision to go after the stuff on my own dime in the best interests of the community, because I can better serve customers when the equipment is near me instead of in Ohio.

Doing any actual work is still a ways off, I have to complete outfitting my garage for operations and set up all the necessary utilities like electrical power and gas/air lines. Safety is a concern for me as well, so I'll likely wind up with fire hoods over the pieces with open flames to make sure I don't burn the place down. Should make the insurance people happy as well.

I'll post more updates as they become available, but for right now know that I'm committed to bringing an effectively dead service back to the community in the not so distant future. I just hope you collectors out there are ready to uphold your end and actually buy some tubes. lol

Nick

Where are you in Southern Maryland? I'm in Northern VA. Dunno how much help I could be right now, but I can't imagine it would hurt to have someone learn to use some of this stuff at 21.

Actually, come to think of it, as a recently graduated film student, do you think it would be a good idea to do a sort of documentary on the process? Having sort of edu-video of tube rebuilding would help preserve the knowledge for the future. I'm a screenwriter myself, but I know people who make documentaries.

That sounds like a pretty great idea. There was a long video shot shortly before Hawkeye shut down; it's interesting (for the handful of us that are obsessed with this stuff and actually understand what's going on) but I think it would be dull and way too dense for most people.

There was a long piece on The Verge not along ago talking about vintage TVs (kinda) and that touched on the subject as well. The article was pretty much a shitshow, written by someone who appears not to understand the distinction between a CRT and a TV that uses a CRT. But it was widely circulated and discussed, and I think it's a subject that would be fascinating to a large number of people, provided it were a well told story with a narrative and so on.

I think you should try to do it.

Maybe you should write the EIA (or successor of same) for the designation of this unique tube.

Looking at Frank's tube site, the last 17" CRT code was the 17EZP22*, so I guess you have the world's only 17FAP4.

*noting the real oddity of the 17QCP(n) series available with many different types of phosphor.

There is a bit of information available, but unfortunately no formal video documentation / training film of the process.

Bob Galanter documented Scotty performing the operations at Hawkeye and I put his video online. Jerome Halphen and Nick Williams also recorded video of Nick's apprenticeship at RACS before they closed, which I have posted in unedited form.

https://www.youtube.com/playlist?lis...Uwq-L41psfpLJQ

If we ever have Scotty come by to do training at the museum I do plan to make a full, formal documentation of the process and his instructions.

I'd gratefully accept any assistance you'd be willing to offer regarding Early Television Museum videos.

-- Dave Sica 732-382-0618

CRT Rebuilding update
 

Has Scotty been approached about coming to the ETF Museum to do training? If say a formal invitation/request should be made (if it hasn't already).

Need to have someone for him to train, and right now there is no one who has stepped forward as a candidate. Nick is currently the only person in our circles who knows how to do this and he's already quite skilled enough that bringing Scotty out to work with him would not be worthwhile.

I see. I wish I could contribute to this in some way, but I'm a newbie in the arena of TV repair and lack the domain experience with this stuff.

I've watched the videos of Scotty doing the rebuilding and I can see that it is the kind of work that you probably need to do a lot of to get good at it. It also seems to be the sort of thing that is learned through "tribal knowledge" and can't be taught through books & videos alone.

Have you considered writing a manual on "how to do it" ?? It seems like this is a lost art, that you and the museum are hoping to ressurect. Might be a good idea to see that it does not get lost again. I can volunteer to edit, proof, and even write from notes, but I have no experience with either glass or making tubes, although 'back in the day' I sure installed a lot of them.

I am in Ohio, and am currently working on restoring the museum's TK41 color camera. Working on a test equipment museum of my own, so I cannot, sadly, step up to learn the tube making process, much as I'd like to help out in this effort, but perhaps I can contribute in an educational way.

Barry

There hasn't been an update since mid 2018... I'm assuming these projects have all been forgotten.. So much for getting these duds rebuilt.. Oh well I guess landfill it is..

I have some of my own opinions and ideas on this subject. To me, the glassworking aspect is the most difficult part of the entire process. From what I have been reading, the high temperature bakeout is not strictly necessary, and is mostly to get shorter pumpdown times. There is no economic pressure to get product shoveled out the door quickly, so doing low temperature bakeout could cause fewer problems related to that. Also, there are improved diffusion pump oils and vacuum pumps available now that will help get a better vacuum than was possible in the past. Why settle for good enough if a better result is possible and would pay dividends in longer tube life?

It seems to me there is a bit of impatience growing in the vintage TV community about not being able to get a CRT rebuilt. Not on my part, but only stating what I have seen lately.

Duds take up a sizable chunck of space. All my monochrome duds are crunched up in the landfill, same for all rectangular color duds. I gave away my glass roundy color duds that I haven't seen make a raster (since that's the only way to confirm the shadow mask and phosphor aren't damaged) and now only have 2 weak monochrome CRTs, 3 round glass colors (21FBP/FJP22), 1 maybe 2 21AXP22s and a 15GP22 waiting a chance to get rebuilt... I'd have no problem sinking ~$1200 into rebuilding the 3 21" color CRTs I've got if the service was available.
If I lived closer than 8 hours drive from the ETF I'd probably volunteer a weekend a month to learn the process and do rebuilds for them...I can't see it being profitable to pay someone to do it but if I donated my time a rebuild has to be worth more to the owner of a CRT than the materials and equipment running costs. If I had more space and fewer high dollar life goals I'd probably try to get my own rebuilding equipment. It's amazing to me that the ETF can get enough voulenteer time and effort to build a rebuilding shop but nobody is willing to take time to do actual rebuilds...There ought to be someone in the region with time on their hands and interest in keeping CRTs going.

It also amazes me that shops that currently rebuild modern CRTs won't take the job... you'd think if we got 10-100 CRTs of the same type like 21FBP22, 10BP4 or 12LP4 that some company would see it as a big enough job to be worth while.

The longer this goes on, no ability to have a CRT rebuilt, the more potential rebuild candidates will end up in the trash instead.

I would need to acquire a vacuum setup with the ability to measure the vacuum to try out things like low temperature bakeout. I have only a junky HVAC pump, and that of course is not enough for this kind of work. I don't know if any of the mom and pop type rebuilding equipment came with high vacuum gauges. So much of the information I find about procedures looks rather empirical to me; it just says pull a vacuum for so much time, then activate the cathode according to a time schedule. It would be better to measure the vacuum and determine when to do things according to that rather than an empirical guess based on time.

Also, I would like to see if gun rebuilding can first be done on a monochrome tube, which should be easier and serve as a proof of concept. IMO too much time and effort was spent on 15GP22 tubes, these should be left for last after getting proficient with monochrome tubes first, then the all glass color tubes.

Potential candidate
 

I always though something like this would be ideal for that Glasslinger guy on YT. The guy has lots of glass experience and seems to be highly intelligent although it is just one guy and up in years at that.

Ooooooohhhhh Oh this sounds great. A CRT re-builder would be somewhat in demand given the retro gaming niche and collector niches...

Honestly, the glasswork part of it seems like the easiest part to me. (Or maybe second easiest, behind cooking the tube under vacuum.) Something that you merely need to practice a bit. Not to mention that there are plenty of glass blowers in the world, the skill is very much alive. Building a gun seems more difficult but not impossible, but that skill is largely forgotten.

Now, the real hard part is the equipment like the specialized lathes and glass torches. And materials, like gun cathodes and getters.

I'm not sure why some of you seem to think baking out during applying vacuum is such a big deal. It simply means the tube is in an oven during the time the vacuum is drawn. Having the tube in some sort of enclosure at that stage is a good idea anyway because the tube may implode when vacuum is drawn. Equipment with this arrangement is available, if not common.

One of the major difficulty when re-building CRTs is the gradual heating and cooling of the glass when making a glass-to-glass joint. If not done correctly the glass will crack. A crack cannot be "welded" closed, the cracked section has to be cut off, you can only do that a few times before too much of the original neck is cut off. If the crack happens when the glass "button" on the end of the gun is attached the whole gun assembly probably has to be replaced. There are many glass formulas, they react to heating differently. Most CRT are made of a type of glass that is not the easiest to work. If you will notice, Glassslinger uses Pyrex glass. Pyrex does not expand with heating like most other glasses and so it rarely cracks. You cannot directly join Pyrex with CRT glass.

Nick (miniman82) is supposed to retire this year. He will then have time to work on his re-building shop and eventually start rebuilding CRTs.

That's not a bad idea. Up in years maybe but I was impressed by his spry...ness(?) in his video making a HV power supply. I wonder if he'd be willing to lend a hand. He's based in TX.

Pyrex glass is a "hard" glass and therefore quite easy to work with and resistant to thermal shocks. The expansion coefficient is around 33x10 ^ -7. The situation is different with sodium and lead glasses, which are "soft" glasses. The expansion coefficient is 94 ... 106x10 ^ -7. The error in cooling and join will unfortunately break.
I mainly use soft glass to build my electron tubes, so differently to Glasslinger.

But let's go back to the regeneration of picture tubes.

I have the biggest problem with extending the "necks" of the cathode ray tubes because I do not have a large horizontal glass lathe. I perform this operation in my hands. This is possible for small picture tubes, but it's a problem for bigger.

Getters are not a problem for me. I have a lot of this parts, Italian production SAES and Polish (UNITRA ZAP). I have a lot of glass sockets and I can do sockets in laboratory scale. The construction of electron guns for black and white CRTs is possible, especially for simple types of electron guns (triode or tetrode type).

In the attachments there are some pictures of the CRT with my electron gun. This is the first cathode ray tube in which I have done almost everything: I replaced the phosphor, replaced the aquadag, and mounted an electron gun of my design. The bad contrast is because the cathode is too close to Wehnelt. Focusing and deflection is magnetic. There is Ion trap (necessary: I have not metallisation of screen).

This is very interesting Alekz. I know a few people who will follow your progress with interest.

Thanks,

Peter

Thanks to some space above my shop rafters, I have at least 3 dud 21FJP22 for possible delivery to Nick, if he so desires practice CRT's.

One RCA Colorama and two Sylvania RE's fully intact but DOA due to various gun maladies.

Back in the 70s, we came close to buying a CRT rebuilding system from a company out of what I recall was Chicago. They used to advertise them in the back of Radio Electronics etc.

The only good thing is that if we did buy it, I would have tossed all the equipment and materials twenty years ago..

John

I will try out a device for extending the necks of electron guns in the near future. I also made a device for obtaining heaters and covering them with insulation. Wish me luck...

I wish you luck :)

I did more tests with heaters. Not having a hydrogen furnace for as high a temperature as necessary, I made a simple glass device. It replaces the hydrogen furnace. Water electrolysis takes place in the vessel on the right. The purest hydrogen is produced by electrolysis of an aqueous solution of potassium hydroxide on nickel electrodes. It is used here. Gas bubbles can entrain small amounts of potassium hydroxide with them, which is detrimental to the heater insulator layer. Therefore, there is a scrubber in the path of the gas, containing water with a small amount of phenolphthalein. This is where the hydroxide particles are absorbed. The pink color means that the water will be replaced soon. The pure hydrogen flows further into the vessel with electrical feedthroughs. The electric current heats the heater and the process can be controlled by regulating it. The used hydrogen flows out through the siphon with the "glass" on the left. This piece of apparatus is also very important. By lighting up the gas bubbles coming out of here, I listen to see if they are shooting. If so, it means that the hydrogen is still contaminated with air and the apparatus still needs to be flushed with hydrogen. Only when the hydrogen quietly ignites, do I start the sintering process of the insulator.

What a project! Keep up the good work. I hope you've got some help there, or this is going to take a while.... ;-)

Small progress:

https://www.youtube.com/watch?v=MOrJ14dMiMo

It has been a while since I have been on the site. After my current gig (maybe a few years) this could be rite up my ally. Learning how to weld a new gun on a old tube does not seem like rocket science.
Where do we stand on guns? Is their NOS available for the color roundies? Do the B&W tubes require rephosphor and aluminumizing? How would we deal with toxic chemical disposal? Is it feasible to replace cathodes in guns? Does the cesium alloy degrade on cathodes not under vacuum?

One of those questions is easy to answer. The emissive surface of a cathode will be ruined by loss of vacuum. I didn't think caesium was normally used for cathodes but I could be wrong.

I've accumulated some knowledge over the years about CRTs. Not everything by a long shot and sometimes I remember things wrong. However I will mention a few things.
Welding glass tubes is not so much a matter of science but skill, harder to get right than it looks. Note that there cannot be too large a bulge where the joint is on the outside (ID of the yoke) or the inside (sliding in the gun). Also it has to be straight.
Some types of guns might be found. There supposedly is a source in Russia.
B/W CRT do not always need a new phosphor, I think it would be a good idea but several people that plan to re-gun tubes do not plan to do it because of the added complications. If a tube is not aluminized it requires a different type of gun (older design) and those might not be available. Perhaps in that case the old gun has to be reused and the cathode replaced.
It isn't feasible to re- screen color tubes with the state of the art.
I don't know about waste chemical disposal. Depending on local regulation a small amount may not be a problem. "The devil is in the details."
New cathodes have a combination of carbonates (barium, strontium and calcium?). Our Polish friend would know. After the vacuum is applied the cathode is heated and carbon dioxide (CO2) (and perhaps H2O) is released from the cathode leaving the oxides. If the cathode is exposed to air the cathode absorbs CO2 and H2O but not in the right way so it is ruined.
You also have to install a new getter, which I believe contains barium and maybe another metal.

Two types of pastes were used in Poland, based on nitrocellulose and methacrylate gum. Barium, strontium and calcium carbonates were mixed in binder. Appropriate diluents and plasticizers were also added. Thus, depending on the used binder, the products of decomposition during the formation of the cathode were: carbon dioxide, nitrogen, water vapor or carbon dioxide, water vapor. Some carbon monoxide may have been formed as well. In Polish picture tubes, only getters based on a metallic barium were used.
In the residual gases, methane appeared as the dominant gas in the pumping out and gettered picture tube.

There has been an update to the progress of a CRT re-building effort.
This was was added to the ETF website several weeks ago.
I hope I am not overstepping by posting this here. I would have thought he would have added to the thread here himself.
https://www.earlytelevision.org/nick..._5-1-2022.html

Thanks for posting this!

Yeah, thanks! I had kinda given up on progress. Good to see it moving along.

Re: the cathode materials; the information I find is the currently used mixture is 56% BaCO3, 31% SrCO3, and 13% CaCO3 by weight. Then mixed with nitrocellulose lacquer in the proportion of 44% carbonates and 56% lacquer. In the past it was usually Ba and Sr carbonate; the Ca was added later because it was found to improve emission current.

What happens when a tube loses vacuum is the oxides combine with water vapor in the air and form hydroxides, The reaction is reversible under vacuum and with heat, but does not result in a working cathode again for some reason.

During activation, the carbonate compounds reduce to oxides, giving off carbon dioxide, plus whatever gases the lacquer breaks down into. Ideally this process is carried out while still under pumpdown to get those gases out of the tube prior to sealing and getter flashing.

In Poland, completely different proportions of carbonates were used. When heated, hydroxides melt and run off the core. This is supposedly the main cause of bad emissions from air-entrained cathodes.

Out of curiosity, why were they using a different material overseas? (Which also brings up the question - did other vendors over there use different compositions for everything?).

I know Beryllium phosphors were used in fluourescent bulbs in the US until just after WWII, and they were also used in some projection tubes in the US. Did they ever see use overseas in either application? And if so, when did the practice end?

I suppose in general there were many variation of things such as compositions.
Large companies like RCA, Sylvania, etc. could afford to research things. Patents on some things could cause some manufacturers to come up with variations. Company secrets in other words. Coca-Cola and Pepsi-Cola.
Other countries had other large companies and even universities did some research.
The cost and availability in different areas could also effect the formula what was used.

This is fantastic. I hope his enthusiasm has persisted since the posting. If this ever gets up and running, I'll be in line for several rebuilds regardless of the outcome. Whatever it costs, I want to support it! I was so down when I saw the late 2018 posting the project had been abandoned. It may still be on life support but I'm keeping fingers and toes crossed!

Fantastic indeed. Just to make it clear the museum does have all the equipment and dedicated space for rebuilding. Nick has his own similar setup at his place. So we have two complete rebuilding facilities. Two main issues remain, skilled operators and a supply of guns.

I attended the vintage computer fest Midwest recently and there is a growing need for monitor rebuilding in that community as well. There is also the vintage arcade gaming contingency. I think there is a huge potential to join forces.