17 Oct
2011
17 Oct
'11
5:06 p.m.
Hello all,
I recall a while back a thread on dealing with screen rot on ADM-3a terminals - surprising
to me, because I have several of them and have had no such issue. But I do have nasty
looking spots on a HP 9845A screen. Does anyone have specific experience with addressing
this problem on this machine? Just to be clear, it looks like round mold colonies around
the edges of the screen. It's likely that there's an anti-glare coating and
something colonized underneath it. Again, I'm looking for specific details regarding
this machine or another machine of the era using the same screen technology, and how you
eliminated the colonies. :-) Thanks -- Ian
17 Oct
17 Oct
5:33 p.m.
On 10/17/11 5:06 PM, Ian King wrote:
Hello all,
Does anyone have specific experience with addressing this problem on this machine?
The procedure is removal of the RTV between the safety glass and CRT separating the two
by
cutting through the RTV with a hot wire, then reattachment at the corners.
There are some examples on the web.
5:58 p.m.
On 10/17/11 5:33 PM, Al Kossow wrote:
On 10/17/11 5:06 PM, Ian King wrote:
http://www.nekochan.net/weblog/archives/2008/10/adm-3a-screen-r.html
there was a discussion of this on cctalk in 2009
http://www.classiccmp.org/pipermail/cctech/2009-February/063776.html
Hello all,
Does anyone have specific experience with addressing this problem on this machine?
The procedure is removal of the RTV between the safety glass and CRT separating the two
by
cutting through the RTV with a hot wire, then reattachment at the corners.
There are some examples on the web.
19 Oct
19 Oct
10:50 a.m.
what about DEC Rainbow monitors? What about just introducing some bleach and hoping
capillary action pulls it in?
--- On Mon, 10/17/11, Al Kossow <aek at bitsavers.org> wrote:
From: Al Kossow <aek at bitsavers.org>
Subject: Re: HP screen screen rot
To: cctalk at classiccmp.org
Date: Monday, October 17, 2011, 8:33 PM
On 10/17/11 5:06 PM, Ian King wrote:
Hello all,
Does anyone have specific experience with addressing
this problem on this
machine?
The procedure is removal of the RTV between the safety
glass and CRT separating the two by
cutting through the RTV with a hot wire, then reattachment
at the corners.
There are some examples on the web.
20 Oct
20 Oct
12:28 a.m.
I have fixed a few Rainbow monitors suffering from screen mould.
It may be crude but I just removed the outer glass by breaking it into parts
and then peeled off the offending plastic layer.
The tube then goes back into the case and you end up with a narrow gap
between the bezel and the tube.
If you are not used to working with glass and CRT's then this way is not for
you
Regards
?
Rod Smallwood
?
-----Original Message-----
From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org]
On Behalf Of Chris M
Sent: 19 October 2011 18:50
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: HP screen screen rot
what about DEC Rainbow monitors? What about just introducing some bleach and
hoping capillary action pulls it in?
--- On Mon, 10/17/11, Al Kossow <aek at bitsavers.org> wrote:
From: Al Kossow <aek at bitsavers.org>
Subject: Re: HP screen screen rot
To: cctalk at classiccmp.org
Date: Monday, October 17, 2011, 8:33 PM
On 10/17/11 5:06 PM, Ian King wrote:
Hello all,
Does anyone have specific experience with addressing
this problem on this
machine?
The procedure is removal of the RTV between the safety
glass and CRT separating the two by
cutting through the RTV with a hot wire, then reattachment
at the corners.
There are some examples on the web.
1:03 p.m.
I have fixed a few Rainbow monitors suffering from screen mould.
It may be crude but I just removed the outer glass by breaking it into pa=
rts
and then peeled off the offending plastic layer.=20
It's not so mucwh crude and dangerous. And not just when you are doing it
either.
I am pretty sure that that outer glass layer, along with the goo sticking
ito the CRT faceplate is part of the implosion protection of the CRT. If
the CRT implodes (which is rare, I agree, but serios uenough that
manufacturers of TV sets cared about it in the 1950s) the user wil lbe
showered in glass and bits of electron gun. Certainly all the
books/datasheets I've looked at imply this.
Unless you _know_ the outer glass layer has no safety function, I
certianly wonldn't remove it.
-tony
2:18 p.m.
On 20 Oct 2011 at 21:03, Tony Duell wrote:
Unless you _know_ the outer glass layer has no safety
function, I
certianly wonldn't remove it.
In the US, it was not uncommon for old TV manufacturers to use a
separate flat sheet of glass in front of the (unprotected) screen for
just this purpose.
The guy on YouTube, fron what I can tell, does not attempt to use a
uniform layer of PVA to reattach the implosion shield, but merely
sticks the shield on at the edges. I suppose this may be sufficient
for small CRTs.
--Chuck
21 Oct
21 Oct
1:25 p.m.
On 20 Oct 2011 at 21:03, Tony Duell wrote:
Same over here. Before the intruction of CRTs with integral implosion
protection in the early 1960s, TV sets had either a sheet of laminated
safety glass in front of the screen or later a sheet of perspex or
similar. Of course the _very_ early TVs over here didn't bother becasue
the viewer didn't look directly at the screen. The CRT was mounted
vertically with the screen at the top due to the long length of the neck
(small defleciton angle) and you saw the picture reflected in a
front-silvered mirror in the lid of the cabinet, But I digress.
Certainly my 1961 Brimar databook refers to 'Twin Panel Teletubes' which
have a second layer of glass (or plastic in some cases) bonded ot the
screen to and an implostion protection.
Unless you _know_ the outer glass layer has no
safety function, I
certianly wonldn't remove it.
In the US, it was not uncommon for old TV manufacturers to use a
separate flat sheet of glass in front of the (unprotected) screen for
just this purpose.
The guy on YouTube, fron what I can tell, does not attempt to use a
uniform layer of PVA to reattach the implosion shield, but merely
sticks the shield on at the edges. I suppose this may be sufficient
for small CRTs.
I'd not want to be sitting in front of one...
-tony
8:19 p.m.
New subject: yet still looking for a color Rainbow monitor was RE: HP screen screen rot
Ron reminded me. I still don't have one, nor the video card :(
thanks for the advice though Ron
22 Oct
22 Oct
12:01 p.m.
New subject: yet still looking for a color Rainbow monitor was RE: HP screen
Ron reminded me. I still don't have one, nor the video card :(
The colour monitor is essentially useless without the video board, all
you get is green text (not much of a change from some versions of the VR201).
You cna use the video board with the VR201 mono monitor to add grpahics
(in 16 intensity levels IIRC). So th board is the thing to find first.
Once you've done that, you cna use any sync-on-green TV-rate RGB analogue
monitor, it's jsut a matter of wiring the cable.
-tony
20 Oct
20 Oct
12:28 p.m.
what about DEC Rainbow monitors? What about just introducing some
bleach and hoping capillary action pulls it in?
Worth a try I suppose, but I've never heard of that working...
The problem/cure is much the same no matter who made the device. I don't
think either hP or DEC made their own monitor CRTs (HP probably made
'scope CRTs at one point), they are pretty much standard ones.
Does anyone know what causes this? So far -- touch wood -- I've not seen
it in any of my machines. And others have in the same models. What am I
doing right?
-tony
21 Oct
21 Oct
7:26 p.m.
--- On Thu, 10/20/11, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
Does anyone know what causes this? So far -- touch
wood --
I've not seen
it in any of my machines. And others have in the same
models. What am I
doing right?
keeping them dry. It's elementary my dear Watson.
Dec monitors, in my humble experience, are especially prone. Maybe the plexiglass is
further away from the face of the tube, and consequently allows more water and fungi to
get in. Don't know.
22 Oct
22 Oct
9:53 a.m.
Chris M wrote:
--- On Thu, 10/20/11, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I think at least one list member had problems even though the screens were
stored in a dry environment. I'm not sure that anyone's ever got to the
bottom of why it happens to some screens and not others :-(
Does anyone know what causes this? So far --
touch wood --
I've not seen
it in any of my machines. And others have in the same
models. What am I
doing right?
keeping them dry. It's elementary my dear Watson. Dec monitors, in my humble experience, are especially
prone.
It's very much an experience thing for sure - I've seen it mostly on HP
(and a Digico screen which had gone particularly rotten). Maybe it's
traceable to a particular set of CRT manufacturers, or specific plants, or
a specific formulation of bonding used at a particular plant, but I don't
know if we'll ever find out for sure!
For the HP 250 I used some resistance wire connected to a 12V PSU to cut
through the bonding and remove the faceplate. As that was just a static
exhibit machine I just reattached the faceplate by sealing around the edges
though - I'm not sure what best practice is to 'properly' re-seal the
entire plate (I'd be particularly worried about getting air bubbles trapped
in there!)
cheers
Jules
10:13 a.m.
On 22 Oct 2011 at 11:53, Jules Richardson wrote:
For the HP 250 I used some resistance wire connected
to a 12V PSU to
cut through the bonding and remove the faceplate. As that was just a
static exhibit machine I just reattached the faceplate by sealing
around the edges though - I'm not sure what best practice is to
'properly' re-seal the entire plate (I'd be particularly worried about
getting air bubbles trapped in there!)
If one wanted real implosion protection, it might be worth
investigating some of the mylar window films made for the purpose of
containing fragments:
http://windowfilmdepot.com/protection.htm
You could then place the old plastic mask over the mylar film without
any sort of adhesive in the middle--or not--and still be protected.
--Chuck
11:15 a.m.
Chuck Guzis wrote:
On 22 Oct 2011 at 11:53, Jules Richardson wrote:
That's an interesting idea!
I wonder how critical it is to fill the gap between the CRT and faceplate
with something, though? For the HP 250 it was a non-functional display, but
on a working screen will there be problems if there's any air trapped in
there (blooming or reflections off the back of the faceplate, for example)
My memory of the HP 250's screen is that the faceplate didn't precisely
follow the contours of the CRT face - the bonding compound varied in
thickness to accommodate this (about 1mm around the CRT face's center and
4mm at the edges).
I don't know how the faceplates are/were normally stuck in place at
assembly - did they apply bonding compound to the front of the CRT and then
press the plate into it, or did they suspend the plate in front of the CRT,
seal around the edges, then pour/inject the bonding compound into the
resulting gap?
cheers
Jules
For the HP 250 I used some resistance wire
connected to a 12V PSU to
cut through the bonding and remove the faceplate. As that was just a
static exhibit machine I just reattached the faceplate by sealing
around the edges though - I'm not sure what best practice is to
'properly' re-seal the entire plate (I'd be particularly worried about
getting air bubbles trapped in there!)
If one wanted real implosion protection, it might be worth
investigating some of the mylar window films made for the purpose of
containing fragments:
http://windowfilmdepot.com/protection.htm
12:44 p.m.
If one wanted
real implosion protection, it might be worth
investigating some of the mylar window films made for the purpose of
containing fragments:
http://windowfilmdepot.com/protection.htm
That's an interesting idea!
I wonder how critical it is to fill the gap between the CRT and faceplate
with something, though? For the HP 250 it was a non-functional display, but
on a working screen will there be problems if there's any air trapped in
there (blooming or reflections off the back of the faceplate, for example)
There might be slight reflections, but no worse than with the separate
safety glass used in 1950's TV sets.
In the case of your HP250, even thoguh you are not running it it could
still be an implosion risk without the correctl-bonded faceplate.
I don't know how the faceplates are/were normally
stuck in place at
assembly - did they apply bonding compound to the front of the CRT and then
press the plate into it, or did they suspend the plate in front of the CRT,
seal around the edges, then pour/inject the bonding compound into the
resulting gap?
ALmost certialy they applied the bonding stuff to one of the parts (which
one I can't say) and then put them together.
-tony
23 Oct
23 Oct
11:51 p.m.
OK, I still don't have an answer to the question I asked: has anyone here actually
done this sort of work on a HP 9845? I opened up the monitor, but the part number for the
CRT wasn't in evidence. Given the orientation of the tube, I think it's going to
take major disassembly to find that, to see if I can get a reasonable replacement if
that's the route I choose to go. If possible, I'd like to have my action plan in
place before I tear it down to bare bones, so I can get the job done and reassemble things
before I forget where they go.
I've been playing with other aspects of the device and it's all sorts of fun. I
did some simple graphing, which is delightfully straightforward. Something I read
suggested an experiment, and I discovered that it is in fact possible to make changes to a
program *while it is running." For instance, I did a simple PRINT "HELLO"
loop and while it was running changed the line to PRINT "GOODBYE". The output
promptly changed when I stored the new line. I also learned that the capstan rollers in
the tape drives are, predictably, mush, and I have a DC100 tape cartridge to clean out.
-- Ian
________________________________________
From: cctalk-bounces at classiccmp.org [cctalk-bounces at classiccmp.org] On Behalf Of
Tony Duell [ard at p850ug1.demon.co.uk]
Sent: Saturday, October 22, 2011 12:44 PM
To: cctalk at classiccmp.org
Subject: Re: HP screen screen rot
Indeed it is. I wonder if a CRT with the frotn glass removed, but covered
with this material would be safe?
If one wanted
real implosion protection, it might be worth
investigating some of the mylar window films made for the purpose of
containing fragments:
http://windowfilmdepot.com/protection.htm
That's an interesting idea!
I wonder how critical it is to fill the gap between the CRT and faceplate
with something, though? For the HP 250 it was a non-functional display, but
on a working screen will there be problems if there's any air trapped in
there (blooming or reflections off the back of the faceplate, for example)
There might be slight reflections, but no worse than with the separate
safety glass used in 1950's TV sets.
In the case of your HP250, even thoguh you are not running it it could
still be an implosion risk without the correctl-bonded faceplate.
I don't know how the faceplates are/were normally
stuck in place at
assembly - did they apply bonding compound to the front of the CRT and then
press the plate into it, or did they suspend the plate in front of the CRT,
seal around the edges, then pour/inject the bonding compound into the
resulting gap?
ALmost certialy they applied the bonding stuff to one of the parts (which
one I can't say) and then put them together.
-tony
24 Oct
24 Oct
2:09 a.m.
OK, I still don't have an answer to the question I
asked: has anyone here
actually
done this sort of work on a HP 9845? I opened up the
monitor, but the
part
number for the CRT wasn't in evidence. Given the
orientation of the tube,
I think
it's going to take major disassembly to find that,
to see if I can get a
reasonable
replacement if that's the route I choose to go.
If possible, I'd like to
have my
action plan in place before I tear it down to bare
bones, so I can get the
job
done and reassemble things before I forget where they
go.
Yes, on my HP 9845B I removed the plate and cleaned the tube, it's running
without it no (I know the risc, but never saw a crt implode and take my
chances on that)
After you removed the monitor you can quit easily dismantle it, HP designed
those machines to be serviceable.
At www.HP9845.net you can find the schematics of the monitor and in the
service manuals the part numbers.
I'm not sure if there are any differences between the in the USA and German
produced machines.
I've been playing with other aspects of the device
and it's all sorts of
fun. I did
some simple graphing, which is delightfully
straightforward. Something I
read
suggested an experiment, and I discovered that it is
in fact possible to
make
changes to a program *while it is running." For
instance, I did a simple
PRINT
"HELLO" loop and while it was running
changed the line to PRINT "GOODBYE".
The output promptly changed when I stored the new line. I also learned
that the
capstan rollers in the tape drives are, predictably,
mush, and I have a
DC100 tape
cartridge to clean out. -- Ian
You better can use HPDRIVE from Angas at the HP9845.net site, DC100A tapes
from HP are bad.
The magnetic layer loosens or
the belt breaks or they just become spaghetti.
I've had new ones shrink-wrapped, after opening they ran once to become
spaghetti.
You can use new tapes from Athana but you have to increase the write current
slightly (~20%)
Using a HP-IB interface and HPDrive is a much better option, if of cause you
have the HP 98034B HP-IB interface or 98034A revised version and the mass
storage rom. (If not contact me, I think I have one on spare)
The next thing to do is running the exerciser, when it runs al tests ok your
lucky.
Else you probably have to replace the roms by a romboard (see HP9845.net) if
so contact me, I do have the PCB's so you can build one.
When I let produce them I let them make some more, so I can offer them to
other collectors just at cost price + shipping.
-Rik
11:35 a.m.
Ian King wrote:
OK, I still don't have an answer to the question I
asked: has anyone
here actually done this sort of work on a HP 9845?
I think people are responding to the "or another machine of the era using
the same screen technology" aspect :-)
Regarding re-bonding, I just used clear silicone outside the visible area
(but something opaque would have worked just as well) - as I mentioned
somewhere, the gap between faceplate and CRT face on the 250 was reasonably
large, so I'm not sure that most adhesives would form a bead that big and
stay in place.
If it lasts a decade, great - the difficult part was removing the faceplate
and original bonding compound; re-doing the bead around the edges wouldn't
be a major maintenance chore (but I've not dismantled a 9845, perhaps
they're much worse).
cheers
Jules
1:42 p.m.
OK, I still don't have an answer to the question I asked: has anyone
here actually done this sort of work on a HP 9845? I opened up the
monitor, but the part number for the CRT wasn't in evidence. Given the
orientation of the tube, I think it's going to take major disassembly to
find that, to see if I can get a reasonable replacement if that's the
A lot of HP machines make it easy to get the CRT out (the 9836C is
particualrly nice in this respect!). I have the 9845B with the enhanced
mono monitor and from what I remmember, you take the top off the monitor
and the top shield under it, then slide the front bezel up and out
(disconnect the function key cable), take out all the plug-in PCBs
(including the heatsink unit), Unplug the anode cap and base conenctor,
put the thing face up and take out the CRT moutings.
Alas I have no idea how the 'simple' monitor goes together.
route I choose to go. If possible, I'd like to
have my action plan in
place before I tear it down to bare bones, so I can get the job done and
reassemble things before I forget where they go.
I've been playing with other aspects of the device and it's all sorts
of fun. I did some simple graphing, which is delightfully
straightforward. Something I read suggested an experiment, and I
discovered that it is in fact possible to make changes to
a program *while it is running." For instance, I did a simple PRINT
"HELLO" loop and while it was running changed the line to PRINT
"GOODBYE". The output promptly changed when I stored the new line. I
I beleive this was known as 'live keyboard mode' and is very nice. Very
few other machines let you do things like that.
also learned that the capstan rollers in the tape
drives are,
predictably, mush, and I have a DC100 tape cartridge to clean out. -- Ian
They're the same drives (exaclty) as are used in the 9815 and 9825
machines, so looking at repair methods for those might help.
-tony
10:32 a.m.
Tony Duell wrote:
Indeed it is. I wonder if a CRT with the frotn glass removed, but covered
with this material would be safe?
Maybe. They do say "3M Fragment Retention Security Films secure glass in
place during blast, seismic, shatter or 'smash and grab' events" - so I
suppose it depends on what their definition of 'blast' is.
Good point.
I'm surprised there's not a risk of air pockets becoming trapped then,
though. Perhaps it was done under vacuum conditions - which might make it
hard to replicate in a DIY environment.
I'm liking Chuck's window film suggestion more and more, because even if it
can be done without trapping air, there's no guarantee that whatever
substance is used won't deteriorate 5 or 10 years down the line - and I'd
rather not chance whatever modern bonding stuff was used being even more
difficult to remove than the original.
cheers
Jules
If one wanted real implosion protection, it might be
worth
investigating some of the mylar window films made for the purpose of
containing fragments:
http://windowfilmdepot.com/protection.htm
That's an interesting idea! I wonder how
critical it is to fill the gap between the CRT and faceplate
with something, though? For the HP 250 it was a non-functional display, but
on a working screen will there be problems if there's any air trapped in
there (blooming or reflections off the back of the faceplate, for example)
There might be slight reflections, but no worse than with the separate
safety glass used in 1950's TV sets. In the case of your HP250, even thoguh you are not
running it it could
still be an implosion risk without the correctl-bonded faceplate.
Hmm, I wonder if it's worth worrying about - I suspect that the chance is
so small that other threats are far more likely, but still...
I don't
know how the faceplates are/were normally stuck in place at
assembly - did they apply bonding compound to the front of the CRT and then
press the plate into it, or did they suspend the plate in front of the CRT,
seal around the edges, then pour/inject the bonding compound into the
resulting gap?
ALmost certialy they applied the bonding stuff to one of the parts (which
one I can't say) and then put them together.
2:26 p.m.
In the case of
your HP250, even thoguh you are not running it it could
still be an implosion risk without the correctl-bonded faceplate.
Hmm, I wonder if it's worth worrying about - I suspect that the chance is
so small that other threats are far more likely, but still... I
don't know how the faceplates are/were normally stuck in place at
assembly - did they apply bonding compound to the front of the CRT and then
press the plate into it, or did they suspend the plate in front of the CRT,
seal around the edges, then pour/inject the bonding compound into the
resulting gap?
ALmost certialy they applied the bonding stuff to one of the parts (which
one I can't say) and then put them together.
I'm liking Chuck's window film suggestion more and more, because even if it
can be done without trapping air, there's no guarantee that whatever
So do I. And I think it would be safe. My father worked on high vacuum
systems for many years and he says that putting ordinary sticky tpe on
the outside will support the glass sufficiently to prevent a violent
implosion. It's prevent the bits flyign too far. Obviosuly you don't want
a CRT screen covered with sellotape, but I would guess this window film
would be enough.
substance is used won't deteriorate 5 or 10 years
down the line - and I'd
rather not chance whatever modern bonding stuff was used being even more
difficult to remove than the original.
Good point. There appear to be some nice UV-curing adhesives used for
assmebling lens elements, but unlike the old Canada Balsam, they're
impossible to shift. I don't think I'd want to have my CRT reassembled in
a way that I couldn't fix it again if need be.
-tony
3:46 p.m.
--- On Mon, 10/24/11, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
The risk of a CRT imploding is small anyway (has
anyone
here ever seen it
ahppen spontanuously -- hitting a CRT with a hammer or
simialr doens't
count ;-),
what about throwing a rock at a crt's face? Does that count? I did this once a long
time ago, w/some terminals I bought from a library. I hadn't blossomed into a vintage
collector yet, the stuff was just junk back then, so I took at least one of them outside
and proceeded to smash it. I was young (maybe 25), and must have been very bored. All I
noticed was that the rock, which was something of an odd shape, between 1.5 and 2.5 inches
depending on how you measured it, was split in half. Is it possible the implosion split
the rock? That's an on topic question, isn't it?
25 Oct
25 Oct
11:59 a.m.
--- On Mon, 10/24/11, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I think the rock is similar to a hammer :-) Ny point was that while a CRT
wil limplode if you break it, it doesn't happen very offten unless you're
throwing a brick at it or soemthing like that.
The risk of a CRT imploding is small anyway (has
anyone
here ever seen it
happen spontanuously -- hitting a CRT with a hammer or
similar doens't
count ;-),
what about throwing a rock at a crt's face? Does that count? I did this once a long time ago, w/some terminals I bought
from a library. I
hadn't blossomed into a vintage collector yet, the stuff was just junk
back then, so I took at least one of them outside and proceeded to smash
I am wondering why you bought said old terminals if you had no use for them.
it. I was young (maybe 25), and must have been very
bored. All I noticed
When I was 25 I was actively preserving PDP11s etc.
was that the rock, which was something of an odd
shape, between 1.5 and
2.5 inches depending on how you measured it, was split in half. Is it
possible the implosion split the rock? That's an on topic question,
isn't it?
Possible. I think the rock was already weak (perhaps partially cracked)
and the force of the implosion finished it off.
In any case, a terminal CRT is likely to ahve integral implosion
protection, meaning that while it did implode when you threw that rock at
it, the result was nowhere near as violent as it could have been. So
think what it could have been like and thus why I am concerned aobut
removing any implosion protection from CRTs.
-tony
1:36 p.m.
--- On Tue, 10/25/11, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
There was nothing to restore in the case of these terminals I decimated LOL. They worked,
just didn't seem to work w/anything I had. Unfortunately.
I am wondering why you bought said old terminals if
you had
no use for them.
I always loved to tinker. I guess I wasn't imaginative enough at the time to do
anymore w/them then what I did (dismantle them, gawk at the insides). I'm not sure
what my intentions were, I guess I just saw more computering stuff, and they were cheap,
so I said what the hay.
It is funny though how little information is (was?) commonly available back then. I think
my parents bought my Tandy 2000 a few years earlier, and until I took a 2nd job and earned
enough to buy an NEC Multisync II (about 600$ back then, earned that standing guard over
Christmas trees for 3 weeks, in not exactly the best of neighborhoods), I played around
w/surplus monitors to see if I could get a picture w/the T2K's something less then
standard video. And in reality it was all that unstandard. Well, I obtained a gorgeous
actual 15" open frame ttl green monitor (Panasonic IIRC), intended for what I
don't know, from a place in Massachusetts. What little it would have taken to get it
to work, but since I knew next to nothing about electronics and whatnot, I didn't have
the guts to tinker too much. Something might explode/implode I must have thought! I asked
my goofy Fortran professor, and he rubbed his chin and did everything but give me an
answer. You
could wander many community colleges to this day and still not get an answer. I probably
also read something in Byte or somewhere about altering the trimpots inside a monitor and
endangering some part of your body as a result.
it. I was
young (maybe 25), and must have been very
bored. All I noticed
When I was 25 I was actively preserving PDP11s etc.
27 Oct
27 Oct
12:49 p.m.
I am wondering
why you bought said old terminals if you had
no use for them.
I always loved to tinker. I guess I wasn't imaginative enough at the
time to do anymore w/them then what I did (dismantle them, gawk at the
insides). I'm not sure what my intentions were, I guess I just saw more
computering stuff, and they were cheap, so I said what the hay.
It is funny though how little information is (was?) commonly
available back then. I think my parents bought my Tandy 2000 a few years
I am not convinved it's much better now. OK, we do have the web now, and
there are some useful wrb sites, but the number of useful books has
certainly decreased. I can remember when there was a bookshop in London
that sold IC databooks (and the ARRL publications, and...). It's no more.
The booksshps that remain sell a few introductory books, and the course
texts for the universisties (many of which are not that useful) and
little else. There's nothing to compare with some of the older books that
are (sometimes [1]) on my bookshelves.
[1] The rest of the time I am reading them, of coruse.
And there are plenty of things that I've wanted to find information on
where hunting round the web (Google searches, checking fora/mailing
lists, etc) ahs found nothing useful (or nothing at all).
earlier, and until I took a 2nd job and earned enough
to buy an NEC
Multisync II (about 600$ back then, earned that standing guard over
Christmas trees for 3 weeks, in not exactly the best of neighborhoods),
? I played
around w/surplus monitors to see if I could get a picture w/the
T2K's something less then standard video. And in
reality it was all that
There are many video 'standards'. To misquote Brian Kernighan, every
machine shpuld have one of its own :-)
unstandard. Well, I obtained a gorgeous actual
15" open frame ttl green
monitor (Panasonic IIRC), intended for what I don't know, from a place
in Massachusetts. What little it would have taken to get it to work, but
since I knew next to nothing about electronics and whatnot, I didn't
have the guts to tinker too much. Something might explode/implode I must
have thought! I asked my goofy Fortran professor, and he rubbed his chin
and did everything but give me an answer.
You;'d prbalby have got more useful infromation talking to a freindly and
knowledgeable TV service guy :-)
You could wander many community colleges to this day and still not get
an answer. I probably also read something in Byte or somewhere about
altering the trimpots inside a monitor and endangering some part of your
body as a result.
Very umliley. I suppsose if the modification/tweaks caused the EHT to
signifciantly rise, you'd get Xrays which can have an adverse effect on
you, but it's not easy to get the EHT to rise by tweaking trimpots. In
any case, you check the EHT with a voltmeter (don't you? :-))
-tony
25 Oct
25 Oct
2:33 a.m.
On Mon, 24 Oct 2011, Tony Duell wrote:
The risk of a CRT imploding is small anyway (has anyone here ever seen it
ahppen spontanuously -- hitting a CRT with a hammer or simialr doens't
count ;-), but it's serious enough that manufactuers bother about it.
Given that there are devices for easily breaking glass that are
essentially sharp points, would a jab from a soldering iron be able to
implode a CRT? I've done this by accident several times. Before anyone
panics, the CRT in question was sent to the recycler years ago.
--
David Griffith
dgriffi at cs.csubak.edu
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?
In the case of your HP250, even thoguh you are not
running it it could
still be an implosion risk without the correctl-bonded faceplate.
Hmm, I wonder if it's worth worrying about - I suspect that the chance is
so small that other threats are far more likely, but still...
12:47 p.m.
Given that there are devices for easily breaking glass
that are
essentially sharp points, would a jab from a soldering iron be able to
implode a CRT? I've done this by accident several times. Before anyone
Possibly. The soldering iron is hot which could set up thermal stresses i
nthe glass too. I do know that soldering to a socket contact while the
socket is plugged onto a CRT or valve can damage the glass-to-metal seal
around the pin, for esample, and is thus a bad idea. Thist doesn't
normally cause an implosion, but...
-tony
24 Oct
24 Oct
8:58 a.m.
In article <4EA2F50B.7090105 at gmail.com>,
Jules Richardson <jules.richardson99 at gmail.com> writes:
Chris M wrote:
There's no evidence that the problem is the result of mold, fungi, or
other living organisms. It is most likely chemical decomposition of
the material used to fill in between the tube and the safety shield.
It is probably just releasing some gas as a result of it
decomposition and creating bubbles in the material.
--
"The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download
<http://legalizeadulthood.wordpress.com/the-direct3d-graphics-pipeline/>
Legalize Adulthood! <http://legalizeadulthood.wordpress.com>
--- On Thu, 10/20/11, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I think at least one list member had problems even though the screens were
stored in a dry environment. I'm not sure that anyone's ever got to the
bottom of why it happens to some screens and not others :-( Does anyone know what causes this? So far --
touch wood --
I've not seen
it in any of my machines. And others have in the same
models. What am I
doing right?
keeping them dry. It's elementary my dear Watson. 
9:58 a.m.
On Mon, 24 Oct 2011, Richard wrote:
There's no evidence that the problem is the result
of mold, fungi, or
other living organisms. It is most likely chemical decomposition of
the material used to fill in between the tube and the safety shield.
Exactly.
It is probably just releasing some gas as a result of
it
decomposition and creating bubbles in the material.
I've done the procedure of removing the shield from an HP2648 terminal,
I've used the hot wire method. I can assure you that the spots are neither
living organisms nor gas bubbles, you'll feel a hard resistance trying to
cut through them. Those spots are hard globules, just like small plastic
balls. Somehow the "silicone" (or whatever the material is) hardens and
gets white, forming those spots. Perhaps there are impurities in the
material that cause a crystallisation of the filler material.
Christian
10:19 a.m.
On observation, your theory makes more sense than the idea this is organic in nature. I
had the monitor apart and there is a very serious bond between the faceplate and the glass
of the CRT, and it's hard to imagine mold, etc. intruding at any point, let alone all
around the edge of the screen!
In a private mail, someone else related using a liquid solvent to remove the silicone
bonding agent, soaking the face in the liquid for about a week. I think I'll try
that, rather than trying to hurt myself with a hot wire. :-) -- Ian
________________________________________
From: cctalk-bounces at classiccmp.org [cctalk-bounces at classiccmp.org] On Behalf Of
Christian Corti [cc at informatik.uni-stuttgart.de]
Sent: Monday, October 24, 2011 9:58 AM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: HP screen screen rot
On Mon, 24 Oct 2011, Richard wrote:
There's no evidence that the problem is the result
of mold, fungi, or
other living organisms. It is most likely chemical decomposition of
the material used to fill in between the tube and the safety shield.
Exactly.
It is probably just releasing some gas as a result of
it
decomposition and creating bubbles in the material.
I've done the procedure of removing the shield from an HP2648 terminal,
I've used the hot wire method. I can assure you that the spots are neither
living organisms nor gas bubbles, you'll feel a hard resistance trying to
cut through them. Those spots are hard globules, just like small plastic
balls. Somehow the "silicone" (or whatever the material is) hardens and
gets white, forming those spots. Perhaps there are impurities in the
material that cause a crystallisation of the filler material.
Christian
3:34 p.m.
--- On Mon, 10/24/11, Christian Corti <cc at informatik.uni-stuttgart.de> wrote:
Those spots are hard globules, just like small plastic
balls. Somehow the "silicone" (or whatever
the material is)
hardens and gets white, forming those spots.
but what I'm talking about is the darkest green imaginable, or perhaps black that is
tainted by the green phosphors.
10:23 a.m.
Richard wrote:
Agreed. I mean, it typically *looks* like some form of living thing, but I
don't think there's ever been any confirmation that it is. In fact, I've
seen numerous screens where the 'spots' are quite far from the screen
edges, so for it to be some kind of critter it would presumably have needed
to be there at the point of manufacture.
cheers
Jules
I think at
least one list member had problems even though the screens were
stored in a dry environment. I'm not sure that anyone's ever got to the
bottom of why it happens to some screens and not others :-(
There's no evidence that the problem is the result of mold, fungi, or
other living organisms.
3:31 p.m.
--- On Mon, 10/24/11, Richard <legalize at xmission.com> wrote:
There's no evidence that the problem is the result
of mold,
fungi, or
other living organisms.? It is most likely chemical
decomposition of
the material used to fill in between the tube and the
safety shield.
It is probably just releasing some gas as a result of it
decomposition and creating bubbles in the material.
It sure looks like mold though. I certainly can't give the final word, but my
original monitor didn't exhibit any mold/stain/?. After, like a fool, I stored it in a
less then moisture tight shed for a time (can't remember, maybe 3-4 years), sho'
'nuf, it molded? up. The 2 I obtained around a year ago came w/the mold? - no extra
charge. They were used in a medical environment, then were in this guy's basement for
who knows how long.
25 Oct
25 Oct
8:15 a.m.
In article <1319495495.64067.YahooMailClassic at web65504.mail.ac4.yahoo.com>,
Chris M <chrism3667 at yahoo.com> writes:
It sure looks like mold though.
Its not mold.
--
"The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download
<http://legalizeadulthood.wordpress.com/the-direct3d-graphics-pipeline/>
Legalize Adulthood! <http://legalizeadulthood.wordpress.com>
18 Oct
18 Oct
1:57 p.m.
Hello all,
I recall a while back a thread on dealing with screen rot on ADM-3a
terminals - surprising to me, because I have several of them and have
had no such issue. But I do have nasty looking spots on a HP 9845A
screen. Does anyone have specific experience with addressing this
problem on this machine? Just to be clear, it looks like round mold
colonies around the edges of the screen. It's likely that there's an
anti-glare coating and something colonized underneath it. Again, I'm
looking for specific details regarding this machine or another machine
of the era using the same screen technology, and how you eliminated the
colonies. :-)
I've (fortunately) never seen this problem 'in the flesh', although I am
told it can affect HP CRTs. Even my 2623 terminal is still perfect.
The front of the CRT is actually 2 pieces of glass bonded together, the
idea beign that it'll act like a car's laminated windscreen if the CRT
inmpodes and will prfecnt glass flying everywhere. The mould develops in
the bonding 'glue'.
There have bene several descriptions of how to cut through this glue and
separa the glass panels withput letting the vacuum out of the CRT.
Running a thin wire, possibly electrically heated, between them is the
scommon way.
But a word of warning. CRT implosion is not at all pleasant. It's perhaps
worth rememebrign that even in the 1940s and 1950s, when we didn't live
in a 'compensation culture', all TVs (or at least all those sold in the
UK) had a safet screen in fornt of the CRT (which did not have a
lamianted glass faceplate at that time). CRT implosion was very rate
(I've met one person who worked in a TV reapir shop and said it happned
to them _once_ in all his time working there), but it was obviouisly
serious enough that the mnufactuerers ddi soemthing about it.
And all the CRT data books I've looked in specifically say that no
attempt must be made ot remvoe the bonded galss faceplate.
Now, as you knowe I gernally approve of repairing rather htan replacing,
so I am not going to suggest you should't try to remvoe the safety glass.
But I do feel that removing it and leaving it out, as some have
suggested, is downright irresponsible. If you remvoe it, you need to
rebond it to the CRT, and make sure the bond is osound. I wonder if the
optical adhasives used for bonding lens elements (the ones that cure
under UV light) are good for this?
I don't baev a 9845A, only a 9845B, and that with the enhanced mono
monitor. But if that's anythign to go by, while there's some complex
circuitry in the monitor (much fo the video generation logic is there),
the actuall monitor seciton -- the CRT and its drivers -- are fairly
convnetional. Is there any reason not to consider replacing the CRT in
your machine?
Thanks -- Ian
-tony
4805
days inactive
4814
days old
35 comments
11 participants
participants (11)
-
aek＠bitsavers.org -
ard＠p850ug1.demon.co.uk -
cc＠informatik.uni-stuttgart.de -
cclist＠sydex.com -
chrism3667＠yahoo.com -
dgriffi＠cs.csubak.edu -
hp-fix＠xs4all.nl -
IanK＠vulcan.com -
jules.richardson99＠gmail.com -
legalize＠xmission.com -
rodsmallwood＠btconnect.com