CRT implosions (was: Re: "screen mold")

Tony Duell ard at p850ug1.demon.co.uk
Tue Oct 4 15:28:57 CDT 2005


> 
> Tony Duell wrote:
> > At least one person here has used a thin wire to cut the bonding, then 
> > removed the front piece of glass, cleaned it up, and rebonded it. It 
> > sounds like a dangerous project to me, not only because the CRT could 
> > implode while you're cutting it, but also if you don't get the bonding 
> > strong enough when you put it back together and the CRT then 
> > subsequnectly implodes, the results would be very unpleasant.
> 
> That does beg the question of under what conditions a CRT implodes. Do 
> age-related implosions happen (or implosions for other reasons other 
> than mechanical shock)? I've never heard of a CRT imploding, except for 
> when physical damage has occured to it - but presumably it does happen.

It is uncommon, but it's so unpleasant if it does happen that they have 
to take precaustions against it. Before the introduction of rimbanded 
CRTs in the 60's (1964 is the date I have for this), all TVs had a piece 
of safety glass in front of the CRT. And remember this was long before 
the current culture of blaming somebody if things go wrong.

I am told, BTW, that several radar operates in planes in the last war 
were killed when the plane had a heavy landing, the radar display CRT 
imploded, and they were litterally shot in the face by bits of the 
electron gun.

Glass can fracture for no apparent reason. It's possible for there to be 
internal stresses, and one day it just fails. You don't want to be 
arround if this happens to an unprotected CRT


> 
> In other words what are the risks - or is it a case of over-engineering 
> in the first place to make sure (to a reasonable extent) that there are 
> no problems out in user-land?
> 
> Also curious as to the extent of the outward blast / debris field (that 
> sounds horribly technical but I can't think of a better phrase!) when a 
> CRT does implode. I'd *assume* glass just extends outward a foot or two, 
> but happy to be corrected there! (of course an explosion would be a 
> rather different matter)

It's not much diffeerent to an explosion. The gl;ass collapses inwards, 
but it doesn't when it gets to the middle. It carries on, and flies all 
over the place.

-tony




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