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-   -   Cataract repairs - are we missing the safety glass aspect? (http://www.videokarma.org/showthread.php?t=270024)

WISCOJIM 01-19-2018 01:22 PM

Cataract repairs - are we missing the safety glass aspect?
 
I've seen plenty of threads where people "fix" a cataract, and I have also done many myself in the past. But I always had this feeling that the way we are sealing these jugs is all wrong.

Does anyone really believe that taping or caulking really makes the CRT front "safety glass"? If you think sealing only the edges of the now cataract free CRT gives you any real protection, you are fooling yourself. Why do you think that inner layer was put in there for in the first place? No, not just to keep dust out...

Real safety glass requires that the inner layer holds the front and back glass together, just like in automotive windshields. Removing that layer just gives you two pieces of glass with an air gap.

Has anyone tried doing it the correct way using a resin between the CRT and the "cover glass"? If so, please share details.

I think we all should reconsider how we remove cataracts, and come up with a way to put the "safety" factor back in.

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Kamakiri 01-19-2018 01:46 PM

I'm all for it....if there's a way.

Tom9589 01-19-2018 02:04 PM

I fully understand the principle behind automotive safety plate glass. Why did we go for so long with a separate safety glass with a huge air gap between the glass and the CRT? Also consider CRTs with no safety glass, just a band around the tube under tension. All you want is that the safety glass stop the CRT glass from being projected outward toward the viewer, not hold it in place like a windshield.

ohohyodafarted 01-19-2018 02:08 PM

You are correct. Little protection is given by taping the safety glass to the crt.

That said, as hobbyists, we do not have the materials or equipment to do this kind of rework.

Even at Hawkeye, a fairly large crt rebuilder, the safety glass was fastened in place with a bead of silicone sealant and carton sealing tape around the circumference. If Hawkeye didn't have the resources to bond the safety glass, then I think it unreasonable to think we can do it.

WISCOJIM 01-19-2018 02:54 PM

Quote:

Originally Posted by Tom9589 (Post 3195034)
I fully understand the principle behind automotive safety plate glass. Why did we go for so long with a separate safety glass with a huge air gap between the glass and the CRT?

Don't mistake plate glass for actual safety glass. I know that a lot of the 1950's TVs I junked in the past did have actual safety glass (with the internal bonding agent) in front of the CRT. And that safety glass was between the CRT and the viewer.

Quote:

Originally Posted by Tom9589 (Post 3195034)
Also consider CRTs with no safety glass, just a band around the tube under tension.

I'm assuming in the case of those CRTs there were improvements in the glass to bring up the safety margin.

Quote:

Originally Posted by Tom9589 (Post 3195034)
All you want is that the safety glass stop the CRT glass from being projected outward toward the viewer, not hold it in place like a windshield.

With the force of an implosion, a sheet of glass offers little actual protection to keep the front glass from shattering and sending its own shards everywhere.

I would imagine in every instance where a CRT was designed with the resin layer, it was there for a specific safety reason. Otherwise they would have come with just an edge bonding in the first place.

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old_tv_nut 01-19-2018 03:00 PM

There were both glass scatter tests and specifications and impact tests/specs over the years, I don't think we can definitively say that the resin bonding was intended specifically to limit scattering, or only to meet the impact tests. If there is someone around who has access to the historical development of UL tests, or very unlikely, some manufacturer's documents (boy, would they not want that to be public), I think we can't say. The resin bond MAY have been mainly for dust exclusion, while the glass continued to provide the same protection as when it was air-spaced.

Can someone who has witnessed breaking a resin tube tell us if it captured all fragments like a windshield, or did glass pieces spray?

If the latter, then the resin may have reduced the force/distance of the spray, or may not. Actual test results with/without resin would be needed to answer this.

TUD1 01-19-2018 03:56 PM

I've done several cataracts and I don't really worry about implosion all that much. I once did a cataract removal on the bathroom floor in my pajamas. A few months ago, I needed to bust up an old dead Zenith 25GP22, and even with a good sized sledgehammer, it took a lot of force to get it to pop.

madlabs 01-19-2018 08:07 PM

Quote:

Originally Posted by TUD1 (Post 3195041)
I've done several cataracts and I don't really worry about implosion all that much. I once did a cataract removal on the bathroom floor in my pajamas. A few months ago, I needed to bust up an old dead Zenith 25GP22, and even with a good sized sledgehammer, it took a lot of force to get it to pop.

Worry? No. Take sensible and reasonable precautions? Hell yes! I've never done a cataract removal but have popped a few CRT's in my youth (back in the early 7's we didn't know better!) and they can really throw some glass sometimes. A piece in the eye would really ruin your day. I'd be wearing a face shield, some gloves and a jacket. Maybe it goes back to my firefighter days, we did crazy stuff but with proper gear.

What about the air gap between a Predicta CRT and the plastic safety screen?

TUD1 01-19-2018 08:25 PM

A piece of glass in an eye? Meh. I've got two of 'em.

MadMan 01-20-2018 12:17 AM

I've said this before, just buy a shitload of UV-activated LOCA glue. It's the stuff they use to glue cell phone's glass to the screen. Kind of expensive for that much, but hey, that's the price of 'safety.'

Game is hard.

Also, while I agree that the mushy stuff between the CRT and the safety glass does definitely add some protection... I'm pretty sure that if the tube wanted to implode, anybody in the vicinity would have a really bad day, whether or not it had the mushy stuff.

WISCOJIM 01-20-2018 12:24 AM

Quote:

Originally Posted by MadMan (Post 3195054)
Also, while I agree that the mushy stuff between the CRT and the safety glass does definitely add some protection... I'm pretty sure that if the tube wanted to implode, anybody in the vicinity would have a really bad day, whether or not it had the mushy stuff.

And I'm sure it would have given more protection when the tubes were fresh, and not with 50+ year-old crusty mushy stuff like we see nowadays.

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reeferman 01-20-2018 01:54 AM

Life was simpler then.

[QUOTE=Tom9589;3195034]I fully understand the principle behind automotive safety plate glass. Why did we go for so long with a separate safety glass with a huge air gap between the glass and the CRT?


We had a 21FB set with come in with a BB hole in it that went through both the safety glass and the CRT face glass. Just left a hole the size of the BB. We couldn't believe it. A one in a million shot, kid.

BTW, there was no "huge air gap".

MadMan 01-20-2018 03:17 AM

Quote:

Originally Posted by reeferman (Post 3195059)
We had a 21FB set with come in with a BB hole in it that went through both the safety glass and the CRT face glass. Just left a hole the size of the BB. We couldn't believe it. A one in a million shot, kid.

Must've been one hell of a bb gun. You sure the kid wasn't playing with his dad's .22?

WISCOJIM 01-20-2018 08:53 AM

1 Attachment(s)
Quote:

Originally Posted by reeferman (Post 3195059)
BTW, there was no "huge air gap".

I assumed Tom was talking about those sets that have the CRT about 1-1/2 to 2 inches behind the flush mounted glass on many of the old TVs.

http://www.videokarma.org/attachment...1&d=1516456338

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Tom9589 01-20-2018 09:12 AM

Exactly.


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