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  #61  
Old 01-15-2011, 05:50 AM
julianburke julianburke is offline
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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.
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Last edited by julianburke; 01-15-2011 at 01:58 PM.
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  #62  
Old 01-15-2011, 10:14 AM
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miniman82 miniman82 is offline
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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.
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  #63  
Old 01-15-2011, 10:00 PM
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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.
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  #64  
Old 01-15-2011, 10:32 PM
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David Roper David Roper is offline
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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.
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  #65  
Old 01-15-2011, 11:23 PM
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marty59 marty59 is offline
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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.
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  #66  
Old 01-16-2011, 12:49 AM
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  #67  
Old 01-16-2011, 12:56 AM
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miniman82 miniman82 is offline
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Quote:
Originally Posted by andy View Post
I would bet those rebuilt tubes that lacked their safety glass had a tension band installed.
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.
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  #68  
Old 01-16-2011, 05:02 PM
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  #69  
Old 01-16-2011, 05:34 PM
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miniman82 miniman82 is offline
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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?

Quote:
I hope Hawkeye wasn't sending back rebuilt 21FJP22s with missing safety glass and no tension band unless they customer asked him to turn it into a 21FBP22
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.
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  #70  
Old 01-16-2011, 10:39 PM
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old_tv_nut old_tv_nut is offline
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Quote:
Originally Posted by andy View Post
I never said the bonded safety glass had anything to do with preventing stress on the CRT. All it does is provide a layer of protection for the CRT (in case something strikes, or scratches the screen), and it helps contain the flying glass if it does implode for some reason. I hope Hawkeye wasn't sending back rebuilt 21FJP22s with missing safety glass and no tension band unless they customer asked him to turn it into a 21FBP22.

Using a CRT with the bonded safety glass removed is fine as long as there is a separate safety glass installed (either flat like 50's sets, or curved like most 21FBP22 sets). Using a CRT with no implosion protection is dangerous and should be avoided.

There's a reason every TV ever made (over about 5") has either had a safety glass, or tension band. Using a TV with no implosion protection is like driving without a seat belt. Everything is fine until something bad happens. Unfortunately, you never know when or where a disaster will happen.
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.
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  #71  
Old 01-16-2011, 10:43 PM
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Quote:
Originally Posted by andy View Post
I would bet those rebuilt tubes that lacked their safety glass had a tension band installed.
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.
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  #72  
Old 01-17-2011, 12:45 AM
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  #73  
Old 01-17-2011, 08:06 AM
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miniman82 miniman82 is offline
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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.
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  #74  
Old 01-17-2011, 10:27 AM
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Last edited by andy; 11-18-2021 at 05:12 PM.
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  #75  
Old 01-17-2011, 11:02 AM
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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).
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