Anyone hear the old myth that a CRT could implode if damaged?
 

I was helping someone take the garbage out at the thrift store. They accepted CRT TVs at the time (don't know their policy now) but we had one where the tube turned out to be dead. So, the guy I was working with picked up the TV with the back missing, and yeeted it into the dumpster while I was standing right next to it! I jumped away while ducking at the same time expecting a shower of flying glass everywhere....... but that didn't happen. What DID happen was just a whooshing sound of air filling the vacuum and that was it.

Furthermore, I saw one as a kid where the entire (assembled) TV was dropped. The case was cracked and it never worked again, but the tube didn't implode.

Now, I know the actual screen is pretty thick to be able to handle the vacuum in the first place, and I've heard of them surviving a lot more abuse than an unprotected LCD ever could.

Have any of you actually seen one violently shatter, more so than a regular glass thing? Did it take a deliberate effort to do so or was it something that could have reasonably happened by accident?

It's a lot easier to break the neck of a CRT than the faceplate. If you break the neck all you get is a rush of air. No implosion.

All later CRTs (mid 1960s onwards?) have a tensioned steel band round the rim. This counteracts the pressure on the faceplate. If you smash the faceplate (and it will take a lot of abuse before it breaks) no glass should fly more than a foot or so in front of the set.

I wouldn't want to try this myself unless I was well out of any possible harm's way!

Also note, it is exceptionally dangerous to remove a rim band on sets designed with them, because it is part of what holds the CRT together. It keeps the glass under tension. This applies to modern sets, I don’t think many sets made before 1970 used them

I never thought it was a myth, I've seen it happen. I have a lot of respect for any CRT, banded or not. We installed a new Sylvania 19 inch black and white tube in a customers set and over night it let go, cracked the standing printed boards in two.

Scary thread about real implosion here:

http://www.videokarma.org/showthread...hlight=implode


jr

As a kid starting out in tv repair in the late 60s,early 70s( I got cheap broken 50s TVs from sally ann), if the picture tube was bad,my friends and I would implode the crts( using an empty lot at the end of my alley) by throwing Rocks at the back of the crt.glass everywhere and the boom sounds like a shot gun. A lot of fun for us kids.did it a lot and somehow,nobody got hurt. RonL

Implosion is a thing, and it's more possible the older a set is. Late 40s electrostatic deflection tubes are thin walled all around (some of the magnetic deflection tubes are too), and if chucked at a solid object should implode. The newer the set generally the better the implosion protection unless they were pushing the boundaries of form factor. An example of this cataract removal is a common process on 60s-70s color tubes the RCA process requires solar heat to happen in ones lifetime....Round tubes and second gen rectangular tubes survive it fine, but the first gen rectangular tubes the 23EGP22 is well documented by several collectors to like spontaneously imploding during the process...

You mean under compression, but yes.

My brother and I used to remove the back from random TV sets (all B&W) in our alley in Chicago in the early 1970s, then throw rocks or brick chunks to bust the CRTs. One of them (perhaps a 90-degree CRT with more volume?) went "kaboom!" and we saw flying glass go past us from our safe spot around the corner of a garage.

The one I saw him toss was probably a late 80s or early 90s set, so it makes sense that it would have had the rim band, according to what you guys are saying.

Though they were before my time, I'm aware of older sets that had a separate "safety" glass in front of the actual tube face, and those were probably before the days of the rim band

Your premise that the front glass is thick to handle the vacuum is false. If thick glass were needed, the rest of the CRT including the neck would also have to be thick.

A friend was in a house where one imploded, and her parents had to remove the shag carpet as they were afraid of not being able to get all the glass shards out of it. The children playing in that room never confessed to what they may have done to cause it.

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I threw a (broken) 13" TV out of a 3rd floor walkup into the back alley once, and it made a pretty big boom.

So why do large screen CRTs have thick front glass? :scratch2:

jr

https://www.google.com/search?q=why+...hrome&ie=UTF-8

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Note quite right. The bell, being more arched, can withstand greater compressive force for a given thickness. The faceplate, being flatter, is compressed by the band to make sure that the stress is compressive even in the center, but that means that the compressive stress is even greater at the periphery. If the tube were a sphere, the stress would be equal and compressive everywhere rather than being stronger some places so that the places where it is minimum never become tensile, even with some impact force.