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#1
11-07-2005, 01:16 PM
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cataract surgey success and failure
I was in the process of removing the safety glass from the 21" round jug in my CM home entertainment system, I was very careful to heat the safety glass evenly, then in a moment of stupidty, I took 4 wooden shims and placed them under the end of the safety glass, while heating the center of the tube, the safetly glass cracked and then broke into piece. That's O'k I'll take that tube and shove it into one of my ctc 9's with the front safety glass.
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[IMG] 
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#3
11-07-2005, 05:47 PM
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When you guys talk "safety glass", I assume you mean "tempered glass", correct?
Or is this glass even tempered (like the side window of a car)? If tempered, it will break into 1000 tiny fragments. Real safety glass only cracks, never shatters.
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From Captain Video, 1/4/2007 "It seems that Italian people are very prone to preserve antique stuff."
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#4
11-21-2005, 01:32 AM
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I don't think it refers to any particular type of glass. It's been called safety glass since the earliest days of TV, but I think "safety" meant "It keeps your kids from pounding on the screen with a hammer".
 John
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#5
11-21-2005, 02:40 AM
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I've seen both tempered and safety. Most of the early B&W safety glass was not tempered, but was 2-ply safety glass like an old car windshield. But some of the color flat glass, and the convex safety glass used on non-bonded 60s color sets (Sears, Packard-Bell) with 21FBP22 was tempered. It just about explodes if you bang it on the edge
 Charles
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#6
11-21-2005, 03:22 AM
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In the case of the 21" color tubes I think the safety factor comes from the bonding, if the tube gets broken it will hold the glass shards together the same way it does in a car.
This is one reason I have a problem with the practice of reattaching the safety glass just around the edges of the tube, if it gets broken you are actually going to have twice as much glass flying around! That said, I have a NOS rebuilt tube that I cracked the safety glass on and will have to do surgery on at some point. 
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#7
11-22-2005, 07:56 PM
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I'd imagine it's NOT out of the realm of possibility to get a sillicone that's clear and refill, but making a jig to hold the tube and glass *just right* could be tricky...
Then again, if anyone ever offers a 'refill' service for early color tubes...
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#9
11-22-2005, 11:17 PM
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Quote:
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#10
11-22-2005, 11:19 PM
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Quote:
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#11
11-23-2005, 03:13 AM
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 I used to have fun in the 70s seeing what kind of mayhem various tubes could make. The 21FJ was most impressive if laid face-down, and a spark plug or other harder-than-glass object was thrown at it to strike it right in the middle of the bell. ka-BOOOOOOOOM! The debris field would be about 10'. The front of the tube always held together. On a 21CY or FB, the front would crack apart but not fly anywhere. If you wanted flying glass, a 7JP4 was the way to go! Those are pyrex hardeded glass, and when tossed over the fence into the cement canal, the glass shards and a cloud of sparkling phosphor would go at least 15' in the air. 21" and 27" black & white tubes did quite well too. SHHH; don't say anything but a CBS 19VP22 can make a nice crash if struck right in the middle. The metal flange holds the tube together, but the face plate shatters and sucks right through the shadow mask. Not that any of us want to hear this report nowadays in 2005, but it was fun and nothing wasted in the 70s when this "science experiment" took place.... Ofcourse I wouldn't DREAM of doing that now, except I'd like to do it to a few of those wonderful Zenith A68ACT00X 27" tubes that left the factory with a short-to-be  Charles
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#12
11-23-2005, 02:01 PM
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I killed a bunch of tubes maybe 15 years ago, mostly 25V. What struck me was how thick the faceplate is, & that sure helps. I recall throwing bricks at screens before & they would just bounce off, leaving a chip but no crack. My favorite way to blow one was to set the tv on fire, sit back & watch. When the phosphor starts to darken, look out.
The thought of trying to rebond a crt just makes my head hurt. I suspect the best product would be something self-leveling.
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Bryan
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#13
11-25-2005, 12:05 AM
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I can see using a vacuum or such to pre debubble the sillicone, then pour it slowly...
Frankly, I have NO CLUE how the heck they did it in the factory! My guess for a modern day rebond: Use a suction cup hloder to hold glass in front of CRT at right sapceing. CRT held by jig. Wrap tape around the two as origional. Poke two holes in top - one to let air out, one to add sillicone. Fill with the new stuff - slowly. Beyond that? No clue. I'd hang onto any bonded tubes with bad bonding - they inevitably test great, and let's face it, SOMEONE will SOMEDAY figure this out...
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#14
11-25-2005, 08:51 AM
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Quote:
my guess is that those sheets of silicon were pre-manufactered and heated just enough to create a bond. I cant imagine that they would have poured silicon on each individual tube. The sheet that I removed was too perfect for that. Pretty good process for back then.
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[IMG]
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#15
11-25-2005, 11:32 AM
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the pva was mixed with a catylyst and was near the viscosity of water.
the cover was held with a jig or spacers and the tape applied. a little port was installed in the tape and the liquid pva was poured. bubbles would come to the port which was the highest point. the pva cures.
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i collect and restore vintage radio's,tv's,and ham gear. email for more info
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