17 Apr
2005
17 Apr
'05
11:15 a.m.
Just for info, following up on a discussion a while back :)
I've just removed the faceplate on the CRT for an HP 250 that was
suffering from the dreaded mould. Used a bit of resistance wire as
someone here had suggested, and it was a remarkably easy job. Took
about ten mins to make it all the way across the CRT (although I was
only running from a 10V DC supply - I expect there's a lot of scope for
increasing the voltage without risk of damaging the CRT)
The sealant stuff pretty much just peels straight off the front of the
CRT / rear of the faceplate once the two are separated. A knife blade,
not water, and washing detergent shifted the rest and cleaned everything
up.
I'm not sure about trying to re-seal it; that could go horribly wrong
and leave air bubbles trapped in there. Not even sure what stuff to use.
Padding the faceplace out as necessary right at the edges (where it
won't be visible when everything's back together) is probably the best
course of action and it'll look as good as new when back together.
Next interesting task will be getting the paint off the 250's console
desk though - seems like when they were scrapped someone just went
around with a spray-can and put big X's on anything that was being
disposed of...
cheers
Jules
17 Apr
17 Apr
1:13 p.m.
On Sun, 17 Apr 2005, Jules Richardson wrote:
I've just removed the faceplate on the CRT for an
HP 250 that was
suffering from the dreaded mould. Used a bit of resistance wire as
someone here had suggested, and it was a remarkably easy job. Took
about ten mins to make it all the way across the CRT (although I was
only running from a 10V DC supply - I expect there's a lot of scope for
increasing the voltage without risk of damaging the CRT)
The sealant stuff pretty much just peels straight off the front of the
CRT / rear of the faceplate once the two are separated. A knife blade,
not water, and washing detergent shifted the rest and cleaned everything
up.
Jules,
Thanks for the info. Did you save any of the affected scraps to have
analyzed by a biologist or something? I don't know if you know anyone
over there who would do it for cheap or free but I know someone over here
who can.
Are you certain it was a mold eating at the sealant or was it, as someone
else put forth, a simple delaminating affect which caused the round spots
to appear when the faceplate was pried away from the CRT?
Until some of this gets actually analyzed and confirmed as a mold or
fungus then I won't fully rely that it in fact is such.
I'm not sure about trying to re-seal it; that
could go horribly wrong
and leave air bubbles trapped in there. Not even sure what stuff to use.
Padding the faceplace out as necessary right at the edges (where it
won't be visible when everything's back together) is probably the best
course of action and it'll look as good as new when back together.
If you don't introduce some sort of filler you might have a shadow or
annoying opitcal affect. Possibly.
Next interesting task will be getting the paint off
the 250's console
desk though - seems like when they were scrapped someone just went
around with a spray-can and put big X's on anything that was being
disposed of...
Gasoline (or petrol as you might want to call it :) is supposed to be able
to dissolve spraypaint without affecting the underlying paint. Also, a
naptha solvent should work but only if used carefully (don't apply
directly, apply to a cloth, and work it very lightly and slowly).
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
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2:11 p.m.
On Sun, 2005-04-17 at 10:13 -0700, Vintage Computer Festival wrote:
Hmm, good point. Initially I think we're just going for a static display
anyway, because there are more pressing projects to sort out than this
machine - so it won't be an issue until someone has time way down the
line to actually restore the machine to working condition.
Maybe I should try this same procedure on one of our HP terminals that
have the same problem though, then I can mess around with fillers on
those (or see how well it works without).
Interesting, I'll give that a try on a test area somewhere - luckily the
spray painters missed the built-in keyboard area! Mainly worried about
whatever I use to remove the paint damaging the underlying console table
material...
cheers
Jules
On Sun, 17 Apr 2005, Jules Richardson wrote:
> I've just removed the faceplate on the CRT for an HP 250 that was
> suffering from the dreaded mould. Used a bit of resistance wire as
> someone here had suggested, and it was a remarkably easy job. Took
> about ten mins to make it all the way across the CRT (although I was
> only running from a 10V DC supply - I expect there's a lot of scope for
> increasing the voltage without risk of damaging the CRT)
>
> The sealant stuff pretty much just peels straight off the front of the
> CRT / rear of the faceplate once the two are separated.
Thanks for the info. Did you save any of the affected
scraps to have
analyzed by a biologist or something?
Hmm, nope - but they're just in the bin outside (contained within the
newspaper on which I was working) so if someone does know someone I
could retrieve a piece...
Are you certain it was a mold eating at the sealant
Actually, there was no obvious mould as such on this one - it seemed
more like the sealant had turned to liquid in some places (visible as
'puddles' behind the glass), whilst in others it seemed to have
crystalised into small hard lumps (giving the visible white spots)
So, no sign of visible mould - I wonder if the dark spots sometimes seen
are maybe some form of optical effect; trapped bubbles as you say rather
than being something physically dark in colour.
Our other HP 250 display shows far more signs of the dark 'mould' spots,
so maybe I'll give that one a go now that I know the procedure works.
I'm not
sure about trying to re-seal it; that could go horribly wrong
and leave air bubbles trapped in there. Not even sure what stuff to use.
Padding the faceplace out as necessary right at the edges (where it
won't be visible when everything's back together) is probably the best
course of action and it'll look as good as new when back together.
If you don't introduce some sort of filler you might have a shadow or
annoying opitcal affect. Possibly. Next
interesting task will be getting the paint off the 250's console
desk though - seems like when they were scrapped someone just went
around with a spray-can and put big X's on anything that was being
disposed of...
Gasoline (or petrol as you might want to call it :) is supposed to be able
to dissolve spraypaint without affecting the underlying paint. 
3:19 p.m.
Someone on the list asked me to send them samples from my Imlac
restoration. I've got the email saved here somewhere....
I even bagged up some samples that have not been 'melted off' with
a wire, but I've not gotten them packed to ship just yet (my 'shipping
department has a huge backlog).
----- Original Message -----
From: "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Sunday, April 17, 2005 2:11 PM
Subject: Re: HP CRT mould update
On Sun, 2005-04-17 at 10:13 -0700, Vintage Computer
Festival wrote:
Hmm, good point. Initially I think we're just going for a static display
anyway, because there are more pressing projects to sort out than this
machine - so it won't be an issue until someone has time way down the
line to actually restore the machine to working condition.
Maybe I should try this same procedure on one of our HP terminals that
have the same problem though, then I can mess around with fillers on
those (or see how well it works without).
Interesting, I'll give that a try on a test area somewhere - luckily the
spray painters missed the built-in keyboard area! Mainly worried about
whatever I use to remove the paint damaging the underlying console table
material...
cheers
Jules
On Sun, 17 Apr 2005, Jules Richardson wrote:
> I've just removed the faceplate on the CRT for an HP 250 that was
> suffering from the dreaded mould. Used a bit of resistance wire as
> someone here had suggested, and it was a remarkably easy job. Took
> about ten mins to make it all the way across the CRT (although I was
> only running from a 10V DC supply - I expect there's a lot of scope for
> increasing the voltage without risk of damaging the CRT)
>
> The sealant stuff pretty much just peels straight off the front of the
> CRT / rear of the faceplate once the two are separated.
Thanks for the info. Did you save any of the
affected scraps to have
analyzed by a biologist or something?
Hmm, nope - but they're just in the bin outside (contained within the
newspaper on which I was working) so if someone does know someone I
could retrieve a piece...
Are you certain it was a mold eating at the
sealant
Actually, there was no obvious mould as such on this one - it seemed
more like the sealant had turned to liquid in some places (visible as
'puddles' behind the glass), whilst in others it seemed to have
crystalised into small hard lumps (giving the visible white spots)
So, no sign of visible mould - I wonder if the dark spots sometimes seen
are maybe some form of optical effect; trapped bubbles as you say rather
than being something physically dark in colour.
Our other HP 250 display shows far more signs of the dark 'mould' spots,
so maybe I'll give that one a go now that I know the procedure works.
I'm
not sure about trying to re-seal it; that could go horribly wrong
and leave air bubbles trapped in there. Not even sure what stuff to
use.
Padding the faceplace out as necessary right at the edges (where it
won't be visible when everything's back together) is probably the best
course of action and it'll look as good as new when back together.
If you don't introduce some sort of filler you might have a shadow or
annoying opitcal affect. Possibly. Next
interesting task will be getting the paint off the 250's console
desk though - seems like when they were scrapped someone just went
around with a spray-can and put big X's on anything that was being
disposed of...
Gasoline (or petrol as you might want to call it :) is supposed to be
able
to dissolve spraypaint without affecting the underlying paint.
18 Apr
18 Apr
6:40 p.m.
On Sun, 17 Apr 2005, Jules Richardson wrote:
The HP300 at the Computer History Museum has the same "mold" effects, as
does a 2648 I've got in my warehouse. HP CRTs (especially the elongated
ones found on the mentioned machines) seem to be more typically
susceptible to this effect than other CRTs. I wonder what it is about
them?
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
[ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]
Are you
certain it was a mold eating at the sealant
Actually, there was no obvious mould as such on this one - it seemed
more like the sealant had turned to liquid in some places (visible as
'puddles' behind the glass), whilst in others it seemed to have
crystalised into small hard lumps (giving the visible white spots)
So, no sign of visible mould - I wonder if the dark spots sometimes seen
are maybe some form of optical effect; trapped bubbles as you say rather
than being something physically dark in colour.
7:07 p.m.
New subject: [Bulk] Re: HP CRT mould update
On Mon, 2005-04-18 at 15:40 -0700, Vintage Computer Festival wrote:
The HP300 at the Computer History Museum has the same
"mold" effects, as
does a 2648 I've got in my warehouse. HP CRTs (especially the elongated
ones found on the mentioned machines) seem to be more typically
susceptible to this effect than other CRTs. I wonder what it is about
them?
Yep, I've not seen it on much else. Digico springs to mind, plus a
couple of others that we have whose names escape me right now - but it's
almost exclusively the HP stuff.
Could just be an age-related breakdown on the sealant stuff that for
some reason is almost unique to HP. Or I did wonder if it's some
strange reaction between the sealant and something else - maybe the glue
on the black tape that HP used around the fronts of their screens, or
something odd like that.
Actually, I wonder if most CRTs even have the faceplate like the HP
systems do? Once I removed the faceplate on this 250's display, it was
just like a regular CRT underneath. Maybe the reason it doesn't happen
to other systems is simply that they don't have this additional glass
panel over the CRT in the first place, and it was an HP addition that
isn't normally found elsewhere? I know that sounds silly, but I've never
paid *that* much attention to the front of CRTs on old systems, and the
ones I do remember seem just like normal TV-type CRTs...
cheers
Jules
9:14 p.m.
New subject: [Bulk] Re: HP CRT mould update
On Mon, 18 Apr 2005, Jules Richardson wrote:
On Mon, 2005-04-18 at 15:40 -0700, Vintage Computer
Festival wrote:
Another product where you see this effect consistently is with ADM 3A
terminals.
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
[ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]
The HP300 at the Computer History Museum has the
same "mold" effects, as
does a 2648 I've got in my warehouse. HP CRTs (especially the elongated
ones found on the mentioned machines) seem to be more typically
susceptible to this effect than other CRTs. I wonder what it is about
them?
Yep, I've not seen it on much else. Digico springs to mind, plus a
couple of others that we have whose names escape me right now - but it's
almost exclusively the HP stuff. 
19 Apr
19 Apr
7:49 a.m.
New subject: [Bulk] Re: HP CRT mould update
At 06:14 PM 4/18/05 -0700, you wrote:
On Mon, 18 Apr 2005, Jules Richardson wrote:
Hmm. I've never seen it on one. I expect that the source of the device
and where/how they were stored makes a big difference.
Joe
On Mon, 2005-04-18 at 15:40 -0700, Vintage
Computer Festival wrote:
Another product where you see this effect consistently is with ADM 3A
terminals. The HP300 at the Computer History Museum has the
same "mold" effects, as
does a 2648 I've got in my warehouse. HP CRTs (especially the elongated
ones found on the mentioned machines) seem to be more typically
susceptible to this effect than other CRTs. I wonder what it is about
them?
Yep, I've not seen it on much else. Digico springs to mind, plus a
couple of others that we have whose names escape me right now - but it's
almost exclusively the HP stuff.
9:53 a.m.
New subject: [Bulk] Re: HP CRT mould update
On Tue, 19 Apr 2005, Joe R. wrote:
At 06:14 PM 4/18/05 -0700, you wrote:
Not necessarily. I've seen ADM 3A terminals that are perfect (I have a
couple) and I've seen some that are terrible (I have a couple).
At any rate, this problem has always been described by speculation and no
hard data. It's time we got some real answeres because if this damage can
be halted and prevented in the first place then I'd like to know how and
why it happens.
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
[ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]
On Mon, 18 Apr 2005, Jules Richardson wrote:
Hmm. I've never seen it on one. I expect that the source of the device
and where/how they were stored makes a big difference. On Mon, 2005-04-18 at 15:40 -0700, Vintage
Computer Festival wrote:
Another product where you see this effect consistently is with ADM 3A
terminals. The HP300 at the Computer History Museum has the
same "mold" effects, as
does a 2648 I've got in my warehouse. HP CRTs (especially the elongated
ones found on the mentioned machines) seem to be more typically
susceptible to this effect than other CRTs. I wonder what it is about
them?
Yep, I've not seen it on much else. Digico springs to mind, plus a
couple of others that we have whose names escape me right now - but it's
almost exclusively the HP stuff. 
10:15 a.m.
New subject: [Bulk] Re: HP CRT mould update
At 08:53 AM 4/19/2005, Vintage Computer Festival wrote:
At any rate, this problem has always been described by
speculation and no
hard data. It's time we got some real answeres because if this damage can
be halted and prevented in the first place then I'd like to know how and
why it happens.
Sounds a job for a museum conservator. I would start by talking
to the engineers and QA department of past or present CRT manufacturers.
- John
6 p.m.
New subject: [Bulk] Re: HP CRT mould update
On Tue, 19 Apr 2005, Vintage Computer Festival wrote:
Not necessarily. I've seen ADM 3A terminals that
are perfect (I have a
couple) and I've seen some that are terrible (I have a couple).
At any rate, this problem has always been described by speculation and no
hard data. It's time we got some real answeres because if this damage can
be halted and prevented in the first place then I'd like to know how and
why it happens.
I agree 100%. I suspect that it's not an organism at all, but
merely breakdown of the stuff that bonds the faceplate to the
tube.
Automobile windshields pretty much all exhibit a similar
phenomenon; they get foggy (white) at the corners. It's known to
be deterioration/oxidation of the plastic layer.
Plastics degrade all the time.
But we need someone to test the "mold", which will be tough.
7:43 p.m.
New subject: [Bulk] Re: HP CRT mould update
Tom wrote:
I agree 100%. I suspect that it's not an organism
at all, but
merely breakdown of the stuff that bonds the faceplate to the
tube.
Possible.
But when I was at the UofU, there was a colloquium with some guys
from Evans and Sutherland, talking about their
hemispherical
display system using lots of monitors. They *did* have problems
with mold attacking their optical interface material. They spent
a lot of time and a lot of money investigating it.
So it's definitely known that mold can do that, but it's probably
the case that it can happen by other means as well.
Eric
9:07 p.m.
New subject: [Bulk] Re: HP CRT mould update
At 03:00 PM 4/19/05 -0700, you wrote:
On Tue, 19 Apr 2005, Vintage Computer Festival wrote:
That's completely different from what these CRTs are doing. These have
spots all over and not an even discoloration that starts at the corners the
way that windshields do. I seriously doubt that they're caused by similar
processes.
Not necessarily. I've seen ADM 3A terminals
that are perfect (I have a
couple) and I've seen some that are terrible (I have a couple).
At any rate, this problem has always been described by speculation and no
hard data. It's time we got some real answeres because if this damage can
be halted and prevented in the first place then I'd like to know how and
why it happens.
I agree 100%. I suspect that it's not an organism at all, but
merely breakdown of the stuff that bonds the faceplate to the
tube.
Automobile windshields pretty much all exhibit a similar
phenomenon; they get foggy (white) at the corners. It's known to
be deterioration/oxidation of the plastic layer.
Plastics degrade all the time.
But we need someone to test the "mold", which will be tough.
I would be EASY to test to see if it's an organic compound.
Joe
7:38 a.m.
New subject: [Bulk] Re: HP CRT mould update
At 11:07 PM 4/18/05 +0000, you wrote:
On Mon, 2005-04-18 at 15:40 -0700, Vintage Computer
Festival wrote:
> The HP300 at the Computer History Museum has the same "mold" effects, as
> does a 2648 I've got in my warehouse. HP CRTs (especially the elongated
> ones found on the mentioned machines) seem to be more typically
> susceptible to this effect than other CRTs. I wonder what it is about
> them?
I've seen it on a HP 9835 and several HP 9845s. The 9845s seem to have
it even more often than the 264x terminals in my experience.
Yep, I've not seen it on much else. Digico springs to mind, plus a
couple of others that we have whose names escape me right now - but it's
almost exclusively the HP stuff.
I'll agree with that!
Joe
6:53 p.m.
New subject: [Bulk] Re: HP CRT mould update
I've seen it on a HP 9835 and several HP
9845s. The 9845s seem to have
it even more often than the 264x terminals in my experience.
Oh great.... The one in my HP98780A (enhanced graphics monitor for the
9845) looks OK at the moment, but I guess I'll have the fun of removing
the faceplate sometime...
My 9845 is a somewhat odd configuration. It's a 9845B with the high-speed
language processor, the enhanced monitor (with the hardware graphics
accelerator board, etc) but only 1 RAM board (it's got the standard
ROM/RAM boards for each of the processors too, of course). Personally, I'd
have thought that anyone ordering a machine with those 2 high-performance
options would have stuffed it with RAM too.
-tony
9:11 p.m.
New subject: [Bulk] Re: HP CRT mould update
At 11:53 PM 4/19/05 +0100, you wrote:
I don't know for certain but I suspect that if you keep it in a good dry
environment that it will be fine.
Joe
I've
seen it on a HP 9835 and several HP 9845s. The 9845s seem to have
it even more often than the 264x terminals in my experience.
Oh great.... The one in my HP98780A (enhanced graphics monitor for the
9845) looks OK at the moment, but I guess I'll have the fun of removing
the faceplate sometime...
My 9845 is a somewhat odd configuration. It's a 9845B with the high-speed
language processor, the enhanced monitor (with the hardware graphics
accelerator board, etc) but only 1 RAM board (it's got the standard
ROM/RAM boards for each of the processors too, of course). Personally, I'd
have thought that anyone ordering a machine with those 2 high-performance
options would have stuffed it with RAM too.
-tony
20 Apr
20 Apr
7:57 a.m.
New subject: [Bulk] Re: HP CRT mould update
----- Original Message -----
From: "Joe R." <rigdonj at cfl.rr.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Wednesday, April 20, 2005 1:11 PM
Subject: Re: [Bulk] Re: HP CRT mould update
I don't know for certain but I suspect that if you keep it in a
good dry
environment that it will be fine.
Joe
The CRT on my 9845 was fine, prior to being stored for some years in a
cold and slightly damp (in winter) environment. This was before it was
disposed of by the previous owner, my former employer. It has, of
course, been kept warm and dry since then!
DaveB, NZ
--
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Checked by AVG Anti-Virus.
Version: 7.0.308 / Virus Database: 266.9.17 - Release Date: 19/04/2005
19 Apr
19 Apr
12:12 p.m.
On 18 Apr 2005 at 15:40, Vintage Computer Festival wrote:
HP CRTs (especially the elongated ones found on the
mentioned machines)
seem to be more typically susceptible to this effect than other CRTs.
I wonder what it is about them?
They were all made by Clinton Electronics of Rockford, Illinois?
I have an HP 2640A, a couple of 2645As, a 2647A, and two 64000s; all have
spots to varying degrees, and all of the tubes were made by Clinton.
Any chance your ADM 3A tubes have Clinton stickers on them?
-- Dave
17 Apr
17 Apr
4:46 p.m.
----- Original Message -----
From: "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Monday, April 18, 2005 3:15 AM
Subject: HP CRT mould update
snip
I'm not sure about trying to re-seal it; that could go horribly
wrong
and leave air bubbles trapped in there. Not even sure what stuff to
use.
Padding the faceplace out as necessary right at the edges (where it
won't be visible when everything's back together) is probably the
best
course of action and it'll look as good as new when back together.
I just did the edge thing with sealant for the 9845 CRT I did a couple
of years back-looks fine, although I did have the same reservations
initially. It probably depends on the 'darkness' of the faceplate
whether a filler is needed or otherwise. I left a gap about 20 cm long
top and bottom just in case I had trapped any moisture etc in there,
but should go back (bugger of a job just getting at the CRT in the
9845) and seal it up some day when it's fairly warm.
DaveB,
Christchurch, NZ
--
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Checked by AVG Anti-Virus.
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18 comments
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