20 Sep
2014
20 Sep
'14
3:24 p.m.
On Fri, 19 Sep 2014, Tony Duell wrote:
Thank you for mentioning this. The "instructions" in the link mentioned
earlier in this thread which suggested breaking and prying off parts of
the outer glass and such with a screwdriver made me cringe. I guess it is
true...anyone can publish anything on the web.
A few more points. Every CRT manufacuter that I have seen a databook for
says htat you must not attempt to remove the outer faceplate. OK, they
wanted to sell new CRTs, and they are covering their backsides if
something goes wrong, but... That layer is not there for decoration
AFAIK all post-war TV sets in the UK have had some kind of implosion
protection. Either a 'direct vision' tube with the double faceplate and
tension band or (on older sets) a seprate laminanted glass implosion
screen/ Given that many of siad sets were made and sold at a time when
safety issuees were not taken so eriously (metal-cased devices with no
earth wire were common, etc, I feel that the risks of using an
unprotected CRT must be major.
Given that it appears the adhesive bwetwene the 2 layers of the CRT
faceplate is part of the protection (as in 'laminated glass). I wonder if
a CERT showing 'fungus' (for want of a better term) is actually unsafe.
The adhesive has decayed, will it hold the layers together if the CRT
implodes?
-tony
we got a
nice squary blue tele-tec terminal but the screen is covered
with a lot of spots in the silicone between the safetyglass and the
tube. is there a way to fix that?
AS I understand it, the is due to the decay fo the bonding 'glue'
between the 2 layers of the CRT faceplate. The direct vision tubes (no
separate implosion guard) have a 2-panel faceplate like a car's
laminated windscreen. If the glass breaks it will not fly everywhere.
I would be very careful about following most of the instructions on the
web, which suggest removing and discarding the outer glass panel. You
would not get me to sit in front of a CRT to which that had been done
(my father spent most of his life working on high vacuum systmes and
knew what an implosion could be like!). IMHO removing the outer glass
layer is as irresponsible as removing a safety earth connection or
shorting out a fuseholder. More irresponsible in many ways since a CRT
can implode when the device is not powered up.
I have never had to do this (although I have got soem CRTs that need
doing). I think I would want to remove the outer glas layer intact and
re=bond it, possibly with that UV-curing adhesive used for bonding
lens elements.
Oh yes, do not scratch the inner CRT glass. No matter what is said about
polishing out hte scratches. They are still potential weaknesses,
possible cuases of an implosion.