4 Oct
2005
4 Oct
'05
5:50 p.m.
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:
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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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