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  #31  
Old 11-12-2013, 12:31 PM
Mal Fuller Mal Fuller is offline
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The CTC4 was a good performer, much more robust than the CTC5s.
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  #32  
Old 11-12-2013, 02:31 PM
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Too bad about the crt. Electronic M has a good point, put the tube in plastic, better yet, do what you can to bring it down to a vacuum and then seal it. Even if all you can do is HVAC level vacuum, heat it too and boil out as much water as you can..... Then seal it.
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  #33  
Old 11-12-2013, 03:01 PM
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Originally Posted by Username1 View Post
Too bad about the crt. Electronic M has a good point, put the tube in plastic, better yet, do what you can to bring it down to a vacuum and then seal it. Even if all you can do is HVAC level vacuum, heat it too and boil out as much water as you can..... Then seal it.
I did not seal mine in plastic. There is a plastic CRT insulator to keep prying fingers from touching the metal bell. That insulator is unnecessary with a glass CRT so I have it stored on my removed, dead AXP. Mine still holds some vacuum so I plan to leave it be.

If I was in Phill's position (with a tube that is completely down to air) I'd remove the base and the pinch-off stem and try to fill the tube with a noble gas that is heavier than air. Noble gas is non-reactive(unlike air) so it would be chemically about the same as having the tube under vacuum and, as long as it does not leak out, would preserve the phosphor and metals inside the CRT preventing further corrosion. After filling it through the pinch-off I'd store it face down and seal the pinch-off with caulk or some such.
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  #34  
Old 11-12-2013, 03:18 PM
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Sorry, I misunderstood you.

As to Phil's tube, Any chemical is likely to out-gas something that can react with the phosphorous so I would not seal it with anything but hot wax. I did see in his photos, that he is correct, it does look like some of the elements are corroding.... Since its corroding in the gun area, I wonder if the leak is down there as well... Like at the metal pinch off...?

Anyway, my original thought still is what I would do, Put it in a box, metal, glass, plastic, heat it to 90 degrees, pull a vacuum for a few days, then seal it. If you find the leak, and its down at the gun, then even better, seal it there after trying to get the moisture out.
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  #35  
Old 11-12-2013, 03:40 PM
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Unfortunately, if the tube has been down to air long enough for the gun to start rusting, it may already be a goner. Back when CRT rebuilding was a viable option, rebuilders would generally not accept duds that had lost vacuum, as they weren't considered rebuildable.

The aluminum coating over the phosphors is likely corroded as well as the shadow mask.

As soon as the air came in, the oxide cathode coatings started absorbing CO2 from the air to form inactive carbonates.

At the very least, the gun will need to be replaced. But if the mask or screen is damaged, the tube is worthless.
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  #36  
Old 11-12-2013, 03:49 PM
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Well why don't you just poop on our parade..... : )

Still have to wonder how long it took to form rust on the gun....?

I would still vacuum it and seal it... Even as a test, you gotta give it every chance as the number of usable duds still needs to be protected....
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  #37  
Old 11-12-2013, 03:51 PM
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Phil Nelson Phil Nelson is offline
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Well, when the ETF rebuilding project gets off the ground, maybe I can donate this 21AXP22 as a test subject.

Meanwhile, I guess I'm in the market for a 21" color tube that can be adapted to work in this TV. Anybody got a spare?

Phil Nelson
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  #38  
Old 11-12-2013, 03:52 PM
sweitzel sweitzel is offline
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While all of the above seems logical in regards to elements being damaged by exposure to air, keep in mind that RACS in France when they were still in business a couple years ago successfully rebuilt a necked 15gp22 that was exposed to air for many years. The screenshot after rebuilding seems to indicate that air did not cause any damage to the mask or phosphors.
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  #39  
Old 11-12-2013, 03:55 PM
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While all of the above seems logical in regards to elements being damaged by exposure to air, keep in mind that RACS in France when they were still in business a couple years ago successfully rebuilt a necked 15gp22 that was exposed to air for many years. The screenshot after rebuilding seems to indicate that air did not cause any damage to the mask or phosphors.
Well there ya go-

Better take steps to protect this dud from further oxidation....
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  #40  
Old 11-12-2013, 05:42 PM
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IIRC there were some poor condition phosphor patches (could have been caused by water dripping in) on the necked RACS tube...It was not ruined but it was not perfect either.

I still think a noble gas is better than a vacuum. You can probably get something heavier than helium for about the same price(making it cheaper than sourcing any usable vacuum pump and suitable accessories). Also consider that if you have a poor vacuum (not as good as factory) there WILL still be many corrosive air molecules inside...Make that trapped inside where they will continue to corrode the tube. Noble gas does not react with anything (anything includes metal, glass, cathode surface, and phosphor), and thus will not cause corrosion or degradation to the CRT. If the tube is stored face down, the gas is poured in through the neck, and the gas is heavier than the main constituent gasses in our atmosphere then the noble gas will sink to the bottom of the tube and slowly displace the air upwards and out through the neck. Think of this filling process like like filling the tube with water(don't fill your tube with water), the noble gas has a similar comparative density to air as does water so as you introduce noble gas gravity and negative buoyancy (relative to air) forces it to the bottom and it fills up the tube from the bottom as if you were pouring water in. If the leak is in the face the noble gas may slowly leak out (if the leak is only big enough for air molecules to pass through then heavier and thus larger noble gas molecules won't get through), but if the tube is face down a lot of gas would have to leak out before air could again reach the shadow mask and phosphors. The shadow mask and phosphors are the most critical part to preserve as they are the least replaceable, and permanent damage to them will affect the picture quality of a rebuild more than any other part that can be damaged by air.
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  #41  
Old 11-12-2013, 06:46 PM
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For the noble gas idea to work, you have to know what the oxides will do with those gases present, and know for sure nothing bad can result as the moisture will remain because you have done nothing to deal with it. Bringing a HVAC vacuum and 90 degrees heat will cause the moisture to boil off as its boiling point is greatly reduced. Then if nothing more, you put the tube in a very thick heat sealed bag with a desiccant inside the bag of sufficient size to do some good, and then keep an eye on it as they change color with moisture (as they absorb it). How will you know if the noble gas leaks out ??

There is no reason why people here can't build a drying for storage box where you mail it to whomever needs it, and heat and vacuum the tube for storage, then bag seal it with desiccant for long term storage. You could get a local HVAC guy to run a vacuum on it.
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  #42  
Old 11-12-2013, 07:32 PM
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Nice score.

Vans are nice. I couldn't even fit a 20" Zenith in the trunk of my '11 Impala today.
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  #43  
Old 11-12-2013, 08:55 PM
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I have a line on a good 21FBP22, thanks to a helpful VK member.

I'm open to ideas about how to preserve this 21AXP22 in the meantime, although building vacuum chambers or bake boxes doesn't seem likely. My workshop is in an uproar during some remodeling and half its contents have already been evacuated into other parts of the house.

Phil Nelson
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  #44  
Old 11-12-2013, 09:29 PM
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I don't think the phosphors are in any danger, as long as no liquid water got in there. That 15G RACS rebuild was a wreck and a half sitting around with no gun in it at all, and it's still working just fine to this day. If you wanted to be sure though you could cleave the gun out, then purge it with a slow flow of nitrogen over a few days to displace the air.
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  #45  
Old 11-13-2013, 08:47 AM
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Quote:
Originally Posted by Phil Nelson View Post
I have a line on a good 21FBP22, thanks to a helpful VK member.

I'm open to ideas about how to preserve this 21AXP22 in the meantime, although building vacuum chambers or bake boxes doesn't seem likely. My workshop is in an uproar during some remodeling and half its contents have already been evacuated into other parts of the house.

Phil Nelson
Hi Phil ,

In reading your post about not being able to easily build a vacuum chamber or bake box I got to wondering about the tube's physical position during storage . Specifically , would it make sense to store it in a position of having the screen up and the gun down , opposite of the normal way they come when new in their boxes ? (any new CRT I've ever unpacked was always "face down" in the carton)

I ask this with the idea that if there is enough moisture to rust the gun , and folks have mentioned possible phosphor damage , maybe with it stored screen facing up no moisture will be able to drip off of the gun and damage the phosphors ...
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