the 2nd one definetly shows how deep and loud the boom can be.. sombody needs to do it with a really good microphone..
when i did it.. it felt like sombody hit me in the chest.

Here's a video of someone smashing the 40" screen of a Sony Trinitron with a sledgehammer:
http://www.youtube.com/watch?v=XNojx-r1TY8

:no:

well atleast he took safety into account.
although he should of have worn gloves also.

I was sorta hoping for the shrieks of agony to commence...

comrades
 

Whew, just got done breaking the lens off an FJP- back is killing me. Thankfully I did NOT have an implosion experience. lol

Here's a edited fake video of a guy smashing his TV screen with a hammer and gets blown to the back of the room:
http://www.youtube.com/watch?v=5G0kA845GgM&NR=1

I have intentionally imploded many CRTs but i also had one implode accidentally on me.

It was a mid 60s 23" B/W tabletop set with a bonded lens CRT i had when i was a kid, it was an European style set with a push-through screen so it was very front heavy, it toppled off my outdoor bench while i was unscrewing the back panel to fix it.
The shockwave was so loud it roared all over the neighborhood and scared the crap out of my parents.

Luckily the back panel was still on and the bonded safety lens did its job so the implosion remained 100% confined inside the set.
The set's speaker was totally shredded by the implosion!

I just got back from my folk's house, where I soaked an FJP in methylene chloride for a day in an attempt to melt the PVA out. Yeah, didn't even budge. I ended up breaking the safety glass off, just like the last one.

Im going to try the water trick. I have plenty of crts around here that need the glass removed. I just need to find a container and will let it soak for a month or so.
Its the RCA style that freaks me out. The Zenith green style cut off so easy with a hot wire I dont worry about those exploding.

Yeah, for that one that imploded on me, we gathered up the PVA and I tested some common solvents to see how it would react. I forget what all I used, a short list would include: MEK, denatured alcohol, carb cleaner, brake cleaner. I sat the pva chunks in some sealed containers with the stuff for a week, and NONE of them really changed after that punishment. This was an RCA tube, btw.

Some real life experiences/observations regarding this topic.

In another thread there was a short discussion regarding PVA vs PVB and a comment was made that auto glass uses PVB and that it doesn't suffer cataracts. Well I've run a car restoration shop and cataracts are actually fairly common, especially on vent windows (remember those?) and flat side glass. Have even seen them creep from the edges of some windshields.

Speaking of auto glass...had a first generation Mazda RX-7 that lost one of the spade connectors for the printed circuit defroster on the rear window (which was a hatchback). Removed the window and sat it upside down on some blankets. Using a soldering iron I was able to solder a replacement connector and left it to cool. Maybe 10-15 minutes later glass was raining down after the damn thing exploded. The interesting thing is that this was bonded safety glass AND had a metal frame around it...add to the equation that unlike a CRT there was no vacuum to contend with and I'm now even more ascared of working on picture tubes. Obviously I induced an incredible amount of localized stress. Mazdas may make you go "Hmmm" but in this case I went "WHATTHEHELLJUSTHAPPNED?!"

Regarding whether rebonding the safety glass is stronger (or not) then just sealing it around the periphery I vote that the original full face bond is stronger. Just stands to reason that the bond effectively doubles the thickness of the individual glass layers, plus it probably adds shear strength as well. Think of where plywood gets it strength from, layers of opposing grains of wood PLUS glue in between.

I could be completely wrong but that's my take on it.

The band was just for the mounting lugs ?

Anybody correct me if I'm wrong here but yes, basically it's there for the mounting lugs to easily facilitate installation/replacement. Most tubes as we know had some sort of strapping set-up that mounted the tube to the bezel. There is the exception of some early Zenith Rectangular tubes that mounted in a "surround" then that was then bolted in, and was a PIA to unseat from the old tube during replacement.

Has anybody noticed any cateract conditions with the band/lug type tubes? With all that strapping and shielding was the use of bonding materials eliminated?

As for releasing tubes of vacuum, I remember a safe way was to drill a hole in the anode button after making sure it would remain discharged!

---

I think one way to reduce the chance of an implosion during a faceplate removal is to get the whole CRT as warm as possible before using the heat gun. The one time (so far) that I removed one, I put the CRT in the sun in my back yard for a few hours before starting the removal. It was quite hot, but since I was already wearing gloves for safety, I could pick it up and move it easily.

Okay, folks, here is another one to add to our "collective experience".

Another VK member needed the safety glass off of a 21FJP22. Since I had a couple dud tubes in the attic I decided to pull one off. The crt in question is a used Philco-built tube that was gassy, from all I could tell. Certainly beyond anything a rejuvanator could do. I took it took work and let it sit in the shop for a few days before deciding to work on it today. I started warming it up with the heat gun-I've done 4 or 5 of these before using this method but after reading a couple implosion stories, I found myself unerved this time. I decided it really made more sense to air down this tube. I used my usual method for tubes I'm going to junk-I used an awl to poke a small hole in the ultor. No drama, it went to air in a minute like they usually do. I then flipped the tube back over. I decided instead of using the heat gun I would use a bank of infared lights I have at work. After setting them up it took some time before I started seeing results, maybe 45 minutes or so. I rotated it 30 degrees or so every time I walked by. At one point I looked and saw cracks, which made me think the safety glass had broken, but on further inspection I saw it to be the PVA. It was not until later, when the glass loosened enough to pull off, that I realized that, in fact, the face of the crt had cracked! (see photos) I can only assume this would have also happened had I not aired the tube, in which case I would have woke everybody in the shop up!

Lesson for me: from now on, it will be water only. I just don't trust heat anymore.

I agree, water only, These round tubes are to scarce at this point to risk it. Leave it or soak it.

I still feel good about wire slicing the green halo zenith style ones though.

PVA solvents from the internet
 

PVA is soluble in a number of organic solvents. Solubility of PVA is directly related to the volatility of the solvent; the more volatile the solvent, the more soluble the PVA. Some of the most common solvents, ranked in order from the most volatile to the least, are listed below.



1. diethyl ether (very volatile, water miscible) 2. acetone (best solvent that is commonly used) 3. benzene (very toxic) 4. ethylene dichloride (very toxic, non-water miscible) 5. methanol (toxic, cumulative poison) 6. methyl ethyl ketone (MEK) (toxic) 7. ethanol (denatured alcohols may be toxic) 8. toluene (slightly toxic) 9. xylene (slightly toxic) 10. amyl acetate (slightly water miscible).


This site indicates that PVB should be soluable in Toluene or Ethanol
http://www.ferro.com/NR/rdonlyres/0A...1/0/B75702.pdf

Destroying a tube only to get the faceplate. I cannot express how poor a judgement for a rare tube that can be rebuilt in the future when equipment is available again. If you are afraid, then leave it alone!!! Circuits in the set can be made or modified to make it work again but a tube cannot be made up.

Like sending an antique car to the shredder to save the windshield.

It's not like we'll be able to get them rebuilt any time soon, I have 3 duds that will be sitting for who knows how long? Who cares about 1 roundie tube, more then we know get thrown away every day. It's not like he wrecked a good 21AX or something.

I've asked opinions about these duds more than once. I had also sent a PM to somebody involved in the ETF rebuilding process, without response. Believe me, I am a total packrat and do not toss anything until I am sure it is junk. In this case, I just could not justify holding on to this dud. Here is one reason: why would you need a crt? One of two reasons, either the old tube is worn out, or it is busted. But if you have a worn-out 21" roundie tube, why not just get it rebuilt, instead of using a dud like this one? Anyway, the faceplate will end up on a good crt which could not otherwise be safely used without it. Aside from that tube I have another dud 21FJP22, a good used 21FBP22 and a good used 21" test jig tube with "Test Tube" acid etched into the face. I also have 6 color roundies, all with good picture tubes, and some others could be heading my way. I don't know that I have $200 invested in the whole pile of sets and tubes altogether. So, no, I'm not really going to lose sleep over this one tube. And, no, I wouldn't have touched a 21AX.

You don't have to explain yourself Bryan. I'm just glad your 6th sense kicked in and you didn't become another implosion horror story...or a statistic. :worried:

Bryan- You made a sacrifice and chose your worst tube. Since it was gassy, there would also be the chance that it was going to air. And it would have been a poorer candidate for rebuilding if and when we may ever see that occur. I am a preservationist at heart but you chose wisely, Grasshopper!

You have also provided a valuable lesson to us by sharing what can happen even to a tube that is at atmosphere. As I have mentioned elsewhere I have a Zenith labled RCA coded 21FJ that has the dreaded PVA cateract and the heat method while having been successful (at times) is no doubt stressful on a tube under vacuum and a little more dangerous than I like. This has been a good thread!

On another note, except for the point of originality I wonder if it's really necessary to reinstall the safety glass face. Even though I'd prefer it, I do have a local jobber (in the day) rebuilt 21FJ that was supplied without the safety glass face, back in the early eighties that I purchased. Some rebuilders seemed to have stood behind that decision as well as claiming how much better the picture would look. Granted, the sharpness, contrast as well as the color look outstanding. The tube is in its second installation.

And think of it this way, a 21FJ without its safety glass is pretty much the same as a 21FB. How many times have we handled these tubes as well as older black and white types and have them in various places of storage and have not have not had any issues of them imploding on their own? We seem to understand that the safety glass front does not affect the structual integrity of the tube. However rare, other than from mis-handling or mis-use or an accidental situation does it seem that there will be an implosion.

...

Not that I've seen, Wayne's CTC-5 has a Hawkeye tube in it and there's no band. I seriously doubt the safety glass had anything to do with stress on the tube itself, just look at the way they are attached: they laid the lens on the front of the tube, then injected PVA into it as a bonding agent. I have 2 FJP's with removed lenses in my sets, and they are doing just fine.

...

What tension band? None of the tubes I have had anything like that, except for the square ones. Are you sure you aren't mistaking mounting hardware for a tension band?

When I talked with Scotty, he told me he can't rebuild the tubes without the glass being removed anyway. Wayne's tube has no band, but I'm pretty sure it has flat glass.

AFAIK no roundies had implosion (tension) bands. Any banding, I think, was for mounting only, and not for pre-compressing the faceplate, which is what the true implosion band does. So, impact protection was supplied a separate flat glass or later in some tubes by the bonded faceplate

My rebuilt 21FJP22 from Scotty definitely does not include a bonded faceplate, but it is behind the flat glass on the CTC-5, so it's protected just as much as a 21AXP22 (metal) or more relevant, the same as a 21CYP22 (glass) that was used as a later replacement.

Absolutely not! The tube has to be designed to take a tension band. Ohterwise, applying one is as likely to cause implosion as prevent it.

...

It wasn't on him to remove the glass, it was on you. That means he only ever has the tube in his possession, you would keep the glass. Not that it matters anymore though. :tears:

...

In my case, I didn't supply the dud - just bought the restored tube from Scotty. This replaced the aired 21AXP22 that we gambled on trying (wasn't destroyed or anything, but turned out to be leaky with air evident within a few days).

For the most part this is/was correct.

In fact I just asked Scotty about this and he said that removal of the glass was something he did as part of the rebuild process.

John

Maybe he told me no, because he was getting close to his shut down day and didn't want to deal with it.

You old timers have been there. Turn on the set with the unbonded tube (after CRT replacement) and you find out your Windex job on the face and safety glass was for naught and you got to do it allllll over again. Always got me going. I was never so happy as when we got bonded tubes regardless of the dud.

I was at a car show of all things, when I ran into a guy who said he worked on the CRT line at RCA Lancaster. He said that occasionally, a tube would let go when it was coming down the line (they hung on overhead hooks) and it would cause several in a row to go off, raining glass down on everyone.

He also mentioned that anyone assigned to packing crts had to wear a flak jacket arrangement. Of course, most people didn't so he said all too often, he would hear the implosion, and grab a mop so he could clean up the massive blood trail leading to the infirmary.