cctalk digest, Vol 1 #83 - 27 msgs

From: Robert Greenstreet <gstreet_at_indy.net>
Date: Mon Jul 15 12:59:00 2002

Hello Dave and Tom,

This is my first response to cctalk, so I don't know if it'll "take" or
not. Just a couple of comments: I've also got a CRT with crack outer glass.
I don't know what type of gel they used to bond the CRT to the outer
protective glass, but Tom's suggestion seem plausible--depends on whether
or not the "gel" is soluble by acetone and also whether or not the gel is
destroyed in the process. Even with optic cement, would it be able to fill
large voids left by dissolved gel? I don't have any idea--just asking. If
any void remains, it's going to appear as a large "bubble" in your viewing
area...

Also, I tend to think that gel and protective glass may only be for extra
protection. In the "old days" I used to see lots of CRT's that had no
protective glass bonded to the front. If you broke the front, you broke the
CRT itself. I seem to recall having broken a few of these things with
pellet guns when I was much younger and never getting the hoped-for
catastrophic implosion (my 6th grade science teacher warned us of when he
shot an old TV CRT with a .22 and created a massive and dangerous
implosion. Could it be that older and larger tubes were more dangerous for
some reason??). I don't know. Maybe the glass is thicker these days. I
still respect CRT's, not only for high voltage, but also for possible
imposion dangers.

Good luck on a solution.

Regards,
Robert Greenstreet
gstreet_at_indy.net
-----------------------------------------------------

Message: 20
Date: Mon, 15 Jul 2002 09:16:45 -0500
To: cctalk_at_classiccmp.org
From: Tom Uban <uban_at_ubanproductions.com>
Subject: Re: CRT problem
Reply-To: cctalk_at_classiccmp.org

Hi Dave,

I have a similar problem with a couple of CRTs from my Imlac graphics machine.
After doing some research, the I did locate a company which would rebuild the
CRT for something like $700, with no guarantee that they would not destroy the
tube. They also had expensive replacement tubes, which were not the correct
phosphor.

Another solution, which I haven't tried yet is to remove the CRT from it's
electronics
and soak the face in a bath of acetone for an extended period of time (or
until the
secondary lens is separated from the tube. Once separated, clean and reattach
using optic cement. This was suggested by a friend who repairs large antique
camera lenses. I'm not sure if acetone will dissolve the cement which holds
the
lens to the tube, so a pre-test may be a good idea.

Some people have indicated a fear of removing the lens from the tube face
thinking
that the tube may well implode without it. I do not think that will be the
case, but
I suppose that it is possible. I believe that the lens is simply added
protect from
day to day use for the face of the tube and is not inherently required to
maintain
the strength of the tube against the vacuum inside. In any case, as always,
great
care should be taken to protect you, your eyes, etc. when handling CRTs, as
they
do carry the risk of implosion.

--tom


At 10:18 PM 7/15/2002 +1200, you wrote:
>I have a 10 or12 inch green screen CRT off an HP 9845B I need to clean up. .
>It has been stored in a damp environment and the silicon rubber 'bonding'
>the protective glass screen to the front of the CRT proper has developed
>large mould spots in side itself for an inch or two around the outside edge
>of the screen. I guess I am looking for suggestions as to how to readily
>separate theses two glass items without scratching etc so I can clean and
>rebond them. I thought at first there was a cavity between the glass on the
>CRT face and the protective glass out front- just a seal of silicon rubber
>round the edge- but no such luck-- seems like the silicon rubber stuff
>covers the whole area of the tube face- so I need to chemically remove it or
>??
>Any ideas??
>
>The 9845B is running OK- getting a partial memory test failure at boot up
>but I don't expect that will be too hard to sort. Anyway-- that's next
>week's problem!
>
>Dave Brown
>Christchurch, NZ
Received on Mon Jul 15 2002 - 12:59:00 BST