19 Nov
2018
19 Nov
'18
10:41 a.m.
I recently picked up a Rainbow 100. The PVA between the safety glass and the CRT on VR201
that came with it has broken down and failed badly.
I have seen videos and read about removing the safety glass, cleaning out the PVA, and
reattaching and resealing the safety glass.
All that I have seen basically sticks the safety glass on at its edges and leaves a void
where the PVA had been. It seems to me that the PVA was providing some implosion
protection. Would it work to replace the PVA and attach the safety glass to the tube with
an optically clear adhesive sheet? I have seen that this exists, but have never used it
before.
Also, I have never worked on a CRT before. I am trying to find a local person who can
observe me and stop me from doing something stupid. If I can?t find someone, what am I
more likely to do wrong? How can I be sure I discharged it before touching it?
Finally, a VR201 specific question. I booted the Rainbow over the weekend and, looking
through broken-down PVA, I could see the Rainbow has booted and I could enter DOS
commands. I could also see white retrace lines. What is the likely cause of that on a
35-year-old CRT?
alan
19 Nov
19 Nov
10:52 a.m.
On Mon, Nov 19, 2018 at 10:41 AM Alan Perry via cctech
<cctech at classiccmp.org> wrote:
Also, I have never worked on a CRT before. I am trying to find a local person who can
observe me and stop me from doing something stupid. If I can?t find someone, what am I
more likely to do wrong? How can I be sure I discharged it before touching it?
I have around a dozen or so HP 264x terminals with various states of
CRT decay. Most have developed bubbles in the face of the CRT. Some
are bad enough that the CRT has started leaking goo from the face.
I have no experience doing any cleanup work on these CRT issues. We
should have a CRT restoring party. Anyone else in the Seattle area
have "moldy" CRTs that need some attention, and/or have experience
doing the work?
12:18 p.m.
On Mon, Nov 19, 2018 at 11:41 AM Alan Perry via cctech <
cctech at classiccmp.org> wrote:
I recently picked up a Rainbow 100. The PVA between the safety glass and
the CRT on VR201 that came with it has broken down and failed badly.
I have seen videos and read about removing the safety glass, cleaning out
the PVA, and reattaching and resealing the safety glass.
All that I have seen basically sticks the safety glass on at its edges and
leaves a void where the PVA had been. It seems to me that the PVA was
providing some implosion protection. Would it work to replace the PVA and
attach the safety glass to the tube with an optically clear adhesive sheet?
I have seen that this exists, but have never used it before.
Also, I have never worked on a CRT before. I am trying to find a local
person who can observe me and stop me from doing something stupid. If I
can?t find someone, what am I more likely to do wrong? How can I be sure I
discharged it before touching it?
I have a VR201 that's like this myself, and I've been too scared to try to
fix it. Instead, I've tried bodging together various hacks to try to get
the signal into a modern composite to VGA converter...
Finally, a VR201 specific question. I booted the Rainbow over the weekend
and, looking through broken-down PVA, I could see the
Rainbow has booted
and I could enter DOS commands. I could also see white retrace lines. What
is the likely cause of that on a 35-year-old CRT?
Pics?
Warner
1:01 p.m.
On 11/19/18 12:18 PM, Warner Losh wrote:
On Mon, Nov 19, 2018 at 11:41 AM Alan Perry via cctech
<cctech at classiccmp.org <mailto:cctech at classiccmp.org>> wrote:
I recently picked up a Rainbow 100. The PVA between the safety
glass and the CRT on VR201 that came with it has broken down and
failed badly.
I have seen videos and read about removing the safety glass,
cleaning out the PVA, and reattaching and resealing the safety glass.
All that I have seen basically sticks the safety glass on at its
edges and leaves a void where the PVA had been. It seems to me
that the PVA was providing some implosion protection. Would it
work to replace the PVA and attach the safety glass to the tube
with an optically clear adhesive sheet? I have seen that this
exists, but have never used it before.
Also, I have never worked on a CRT before. I am trying to find a
local person who can observe me and stop me from doing something
stupid. If I can?t find someone, what am I more likely to do
wrong? How can I be sure I discharged it before touching it?
I have a VR201 that's like this myself, and I've been too scared to
try to fix it. Instead, I've tried bodging together various hacks to
try to get the signal into a modern composite to VGA converter...
Finally, a VR201 specific question. I booted the Rainbow over the
weekend and, looking through broken-down PVA, I could see the
Rainbow has booted and I could enter DOS commands. I could also
see white retrace lines. What is the likely cause of that on a
35-year-old CRT?
Pics?
Here is an attempt to use Facebook for image hosting here. If it doesn't
work, I will put the image up on a real image hosting site.
https://scontent-sea1-1.xx.fbcdn.net/v/t1.0-9/46508514_10156808244977208_23…
alan
Warner
1:10 p.m.
Those retrace lines are likely an artifact of the brightness control being
set too high. It's pretty typical with older monochrome TV sets. It also
looks like there's insufficient vertical sweep, probably due to old
capacitors.
On a CRT that small, I wouldn't be concerned about direct fitting the
safety glass over the CRT. In fact, if it has an implosion band, that outer
glass could possibly be for glare reduction only. Some TV collectors use
foam tape around the perimeter of the CRT face as a cushion, then seal the
glass to the face with a good quality tape.
The good news is that PVA is so bad that an hour soak in a tub of warm
water should do the trick. -C
On Mon, Nov 19, 2018 at 3:02 PM Alan Perry via cctech <cctech at classiccmp.org>
wrote:
On 11/19/18 12:18 PM, Warner Losh wrote:
On Mon, Nov 19, 2018 at 11:41 AM Alan Perry via cctech
<cctech at classiccmp.org <mailto:cctech at classiccmp.org>> wrote:
I recently picked up a Rainbow 100. The PVA between the safety
glass and the CRT on VR201 that came with it has broken down and
failed badly.
I have seen videos and read about removing the safety glass,
cleaning out the PVA, and reattaching and resealing the safety glass.
All that I have seen basically sticks the safety glass on at its
edges and leaves a void where the PVA had been. It seems to me
that the PVA was providing some implosion protection. Would it
work to replace the PVA and attach the safety glass to the tube
with an optically clear adhesive sheet? I have seen that this
exists, but have never used it before.
Also, I have never worked on a CRT before. I am trying to find a
local person who can observe me and stop me from doing something
stupid. If I can?t find someone, what am I more likely to do
wrong? How can I be sure I discharged it before touching it?
I have a VR201 that's like this myself, and I've been too scared to
try to fix it. Instead, I've tried bodging together various hacks to
try to get the signal into a modern composite to VGA converter...
Finally, a VR201 specific question. I booted the Rainbow over the
weekend and, looking through broken-down PVA, I could see the
Rainbow has booted and I could enter DOS commands. I could also
see white retrace lines. What is the likely cause of that on a
35-year-old CRT?
Pics?
Here is an attempt to use Facebook for image hosting here. If it doesn't
work, I will put the image up on a real image hosting site.
https://scontent-sea1-1.xx.fbcdn.net/v/t1.0-9/46508514_10156808244977208_23…
alan
Warner
5:28 p.m.
In the video that I looked at, the guy cut 8 1/8" pieces of double-sided
foam tape, three each along the top and bottom and one on each side,
then sealed it with clear packing tape. It seemed to me that using some
optically clear adhesive sheet would accomplish both jobs.
I have some heat pads (gel in plastic that gets thrown in a microwave to
heat up) for loosening the screen adhesive on iPads and such. Can I use
them to get the remaining PVA to loosen up?
On 11/19/18 1:10 PM, Cory Heisterkamp wrote:
Those retrace lines are likely an artifact of the
brightness control
being set too high. It's pretty typical with older monochrome TV sets.
It also looks like there's insufficient vertical sweep, probably due
to old capacitors.
On a CRT that small, I wouldn't be concerned about direct fitting the
safety glass over the CRT. In fact, if it has an implosion band, that
outer glass could possibly be for glare reduction only. Some TV
collectors use foam tape around the perimeter of the CRT face as a
cushion, then seal the glass to the face with a good quality tape.
The good news is that PVA is so bad that an hour soak in a tub of warm
water should do the trick. -C
On Mon, Nov 19, 2018 at 3:02 PM Alan Perry via cctech
<cctech at classiccmp.org <mailto:cctech at classiccmp.org>> wrote:
On 11/19/18 12:18 PM, Warner Losh wrote:
On Mon, Nov 19, 2018 at 11:41 AM Alan Perry via cctech
<cctech at classiccmp.org <mailto:cctech at classiccmp.org>
<mailto:cctech at classiccmp.org <mailto:cctech at classiccmp.org>>>
wrote:
? ? ?I recently picked up a Rainbow 100. The PVA between the safety
? ? ?glass and the CRT on VR201 that came with it has broken down and
? ? ?failed badly.
? ? ?I have seen videos and read about removing the safety glass,
? ? ?cleaning out the PVA, and reattaching and resealing the
safety glass.
? ? ?All that I have seen basically sticks the safety glass on at its
? ? ?edges and leaves a void where the PVA had been. It seems to me
? ? ?that the PVA was providing some implosion protection. Would it
? ? ?work to replace the PVA and attach the safety glass to the tube
? ? ?with an optically clear adhesive sheet? I have seen that this
? ? ?exists, but have never used it before.
? ? ?Also, I have never worked on a CRT before. I am trying to find a
? ? ?local person who can observe me and stop me from doing something
? ? ?stupid. If I can?t find someone, what am I more likely to do
? ? ?wrong? How can I be sure I discharged it before touching it?
I have a VR201 that's like this myself, and I've been too scared to
try to fix it. Instead, I've tried bodging together various
hacks to
try to get the signal into a modern composite to
VGA converter...
? ? ?Finally, a VR201 specific question. I booted the Rainbow
over the
? ? ?weekend and, looking through broken-down PVA,
I could see the
? ? ?Rainbow has booted and I could enter DOS commands. I could also
? ? ?see white retrace lines. What is the likely cause of that on a
? ? ?35-year-old CRT?
Pics?
Here is an attempt to use Facebook for image hosting here. If it
doesn't
work, I will put the image up on a real image hosting site.
https://scontent-sea1-1.xx.fbcdn.net/v/t1.0-9/46508514_10156808244977208_23…
alan
Warner
6:08 p.m.
On Nov 19, 2018, at 7:28 PM, Alan Perry wrote:
In the video that I looked at, the guy cut 8 1/8"
pieces of double-sided foam tape, three each along the top and bottom and one on each
side, then sealed it with clear packing tape. It seemed to me that using some optically
clear adhesive sheet would accomplish both jobs.
I have some heat pads (gel in plastic that gets thrown in a microwave to heat up) for
loosening the screen adhesive on iPads and such. Can I use them to get the remaining PVA
to loosen up?
The heat pads are worth a shot if they can maintain temp long enough to do the job, though
you'll be up against quite a bit of thermal mass with that thick glass. The old trick
that people are still using today with vintage 21" CRT's is to put them in a
kiddie pool outside and let the sun warm the water. You don't want to start too hot
for risk of cracking the glass. *Glances out window* I can tell you that trick
wouldn't work here today, nor for 6 more months.
If you have a way of ensuring the optically clear adhesive sheet bonds evenly and
won't yellow, I don't see why that wouldn't work. I recall someone did do the
foam tape/packing tape operation and then DID fill the void with a PVA type liquid
material. Risky to ensure all the air bubbles made their way out, for sure. -C
25 Nov
25 Nov
11:27 a.m.
The heat pads are worth a shot if they can maintain temp long enough to do
the job, though you'll be up against quite a bit of thermal mass with that
thick glass. The old trick that people are still using today with vintage
21" CRT's is to put them in a kiddie pool outside and let the sun warm the
water. You don't want to start too hot for risk of cracking the glass.
*Glances out window* I can tell you that trick wouldn't work here today,
nor for 6 more months.
If you have a way of ensuring the optically clear adhesive sheet bonds
evenly and won't yellow, I don't see why that wouldn't work. I recall
someone did do the foam tape/packing tape operation and then DID fill the
void with a PVA type liquid material. Risky to ensure all the air bubbles
made their way out, for sure. -C
I did some tiny bit of research into this when I dealt with my HP2640 B and
a VR201. The former was in a condition where just a tiny fraction in the
middle of the screen attached to the glass so it almost fell of by itself.
With the VR201 the story was a bit different. I didn't want to heat it up
like most people seems to be doing when looking at the Youtube clips. I
checked the solubility of the PVA (PVAc really, PVA is something different)
in water and nothing happened at all. I tried to heat the water a bit but
no change. I am not sure how come people are successful with this method.
But I investigated PVAc a bit and found out that it is soluble in various
esters. I bought a bottle of Butylacetate and indeed it made it dissolve
quite well. Butylacetate is mostly used as as solvent for polyester paints,
and I think it is an ingredient in what women use for removing nail polish
(when not using acetone). BTW Acetone is also dissolving PVAc very well but
the boiling temperature is much lower. As far as I can understand
Butylacetate is not very harmful to deal with either.
What I did wash to inject butylacetate using a long needle syringe in
between the front glass and the CRT and let it rest for a few days. I put
some plastic wrap around to contain the butylacetate a bit more and then I
repeated it a couple of times until the front glass simply fell off.
This is the method I will use in future with my other screens that have the
same problem (HP2645, HP9835, HP9845, (Possibly also the Tektronix 4016
depending on the type of front glass used).
/Mattis
2:51 p.m.
Saving this? thread!
Thanks? for the great info and hints? as we have a stack of HP? 254x terminals? and some
of them? graphics? hi end? ones... have? no idea if they? will light off for? not but
thankful to have? even as? static? displays.?
Ed Sharpe? Archivist for? SMECC??
?
?
?
?
?
In a message dated 11/25/2018 12:27:56 PM US Mountain Standard Time, cctalk at
classiccmp.org writes:
?
> The heat pads are worth a shot if they can maintain temp long enough to do
> the job, though you'll be up against quite a bit of thermal mass with that
> thick glass. The old trick that people are still using today with vintage
> 21" CRT's is to put them in a kiddie pool outside and let the sun warm the
> water. You don't want to start too hot for risk of cracking the glass.
> *Glances out window* I can tell you that trick wouldn't work here today,
> nor for 6 more months.
> If you have a way of ensuring the optically
clear adhesive sheet bonds
> evenly and won't yellow, I don't see why that wouldn't work. I recall
> someone did do the foam tape/packing tape operation and then DID fill the
> void with a PVA type liquid material. Risky to ensure all the air bubbles
> made their way out, for sure. -C
I did some tiny bit of research into this when I dealt with my HP2640 B and
a VR201. The former was in a condition where just a tiny fraction in the
middle of the screen attached to the glass so it almost fell of by itself.
With the VR201 the story was a bit different. I didn't want to heat it up
like most people seems to be doing when looking at the Youtube clips. I
checked the solubility of the PVA (PVAc really, PVA is something different)
in water and nothing happened at all. I tried to heat the water a bit but
no change. I am not sure how come people are successful with this method.
But I investigated PVAc a bit and found out that it is soluble in various
esters. I bought a bottle of Butylacetate and indeed it made it dissolve
quite well. Butylacetate is mostly used as as solvent for polyester paints,
and I think it is an ingredient in what women use for removing nail polish
(when not using acetone). BTW Acetone is also dissolving PVAc very well but
the boiling temperature is much lower. As far as I can understand
Butylacetate is not very harmful to deal with either.
What I did wash to inject butylacetate using a long needle syringe in
between the front glass and the CRT and let it rest for a few days. I put
some plastic wrap around to contain the butylacetate a bit more and then I
repeated it a couple of times until the front glass simply fell off.
This is the method I will use in future with my other screens that have the
same problem (HP2645, HP9835, HP9845, (Possibly also the Tektronix 4016
depending on the type of front glass used).
/Mattis
19 Nov
19 Nov
1:48 p.m.
On Nov 19, 2018, at 4:01 PM, Alan Perry via cctech
<cctech at classiccmp.org> wrote:
On 11/19/18 12:18 PM, Warner Losh wrote:
>
>
> ...
>
> I have a VR201 that's like this myself, and I've been too scared to try to
fix it. Instead, I've tried bodging together various hacks to try to get the signal
into a modern composite to VGA converter...
I've been thinking about that. There are assorted converters around for sale but the
trick seems to be the sync on green (rather than separate sync which is common in various
other flavors).
Is there a worked-out design for this anywhere?
Finally, a
VR201 specific question. I booted the Rainbow over the
weekend and, looking through broken-down PVA, I could see the
Rainbow has booted and I could enter DOS commands. I could also
see white retrace lines. What is the likely cause of that on a
35-year-old CRT?
Pics?
Here is an attempt to use Facebook for image hosting here. If it doesn't work, I will
put the image up on a real image hosting site.
https://scontent-sea1-1.xx.fbcdn.net/v/t1.0-9/46508514_10156808244977208_23…
alan
5:12 p.m.
On 11/19/18 1:48 PM, Paul Koning wrote:
Actually, the intensity is turned all of the way up because that is
where it happened to be when I connected everything up. I was so focused
on whether DOS had booted that it didn't even click in my head that I
could adjust the monitor to make it easier to read. I didn't notice that
I had things turned all the way up or even notice the retrace lines
until later when I looked at that picture.
alan
On Nov 19, 2018, at 4:01 PM, Alan Perry via
cctech <cctech at classiccmp.org> wrote:
It looks like you turned the intensity up so far that the retrace didn't
get blanked fully. Not much choice about that given the bad screen, I suppose. Finally, a VR201 specific question. I booted
the Rainbow over the
weekend and, looking through broken-down PVA, I could see the
Rainbow has booted and I could enter DOS commands. I could also
see white retrace lines. What is the likely cause of that on a
35-year-old CRT?
Pics?
Here is an attempt to use Facebook for image hosting here. If it doesn't
work, I will put the image up on a real image hosting site.
https://scontent-sea1-1.xx.fbcdn.net/v/t1.0-9/46508514_10156808244977208_23…
alan
2219
days inactive
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days old
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