CRT implosions

[Dave Brown]

ref the CRT 'mould' issue.

The problem is NOT related to the bond between the CRT face and the 
safety faceplate at all. Any attempt to remove the CRT safety glass 
would be foolish in the extreme. I don't believe you could remove the 
bonded safety glass without permanent damage to the crt and probably 
yourself - except perhaps on very early TV CRTs, (where the safety 
glass was separate anyway) and I doubt there are any of those in 
vintage computer systems under discussion

The CRTs in question have an ADDITIONAL anti-glare or similar screen 
attached to the front of the (permanently) bonded safety glass 
faceplate with some sort of silicon rubber type adhesive. The 
sealant/adhesive between the bonded safety glass on the front of the 
CRT and this additional anti-glare (or similar cosmetic etc effect) 
glass screen is where the problem occurrs.

That said, caution is always required when working with CRTs, but the 
hot wire technique works well to get this issue sorted.

DaveB, NZ


----- Original Message ----- 
From: "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
To: "General Discussion: On-Topic and Off-Topic Posts" 
<cctalk at classiccmp.org>
Sent: Wednesday, October 05, 2005 10:25 AM
Subject: Re: CRT implosions


> J.C. Wren wrote:
>> Some useful information here: 
>> http://repairfaq.ece.drexel.edu/sam/crtfaq.htm#crtcir
>
> Rats, I almost checked there before posting too, but didn't recall 
> any such section on the site!
>
> Interestingly, that info implies that it's the steel strap around 
> the perimeter of the CRT's face which does the implosion protection, 
> and that the laminated faceplate is purely an additional protection 
> against scratches etc. damaging the CRT itself (and therefore 
> introducing greter risk of implosion)
>
> So that article alone suggests that the faceplate isn't there to 
> stop debris at all (although doubtless along with the sealant 
> material it helps).
>
> Still, it'd be nice to hear from people who've actully been involved 
> in manufacturing CRTs I suppose!
>
> I'm tempted to say that replacing the sealant material on anything 
> past 1970 or so is a safe thing to do - providing nobody goes 
> dropping the CRT on its face, and providing that nobody tries 
> smacking the face of the CRT with something heavy. Still, that's 
> just my judgement...
>
> As for implosion risk in using heated wire to remove the 
> faceplate... Hmm. I was careful where I postioned myself when I 
> removed the plate on the HP 250 screen just in case, plus I went 
> evenly from the corners a bit at a time. Given the huge thickness of 
> the CRT face* I would be surprised if heated wire could cause it to 
> break (the faceplate's another matter as it's so thin, which is 
> really why I was being careful about the heating). Just a case of 
> being careful though I suppose.
>
> *I recall breaking TV CRTs apart as a kid and the glass at the front 
> is amazingly thick. Bricks bounce off happily without damaging the 
> screen at all.
>
> cheers
>
> Jules
>
>
>
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