17 Jul
2008
17 Jul
'08
2:29 a.m.
Terminal Buffs and others interested:
I've seen screen rot before -- even owning one with perimeter
symptoms, but this is an example of _extreme_ "screen rot" (separation
of the protective plate from the CRT) on an ADM-3a.
See picture(s) --
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=360070017833
I realize this issue has been brought up and discussed numerous times
in the past -- but I thought I'd give ClassicCMP'ers a peek.
I'm unsure if we've ever come to the conclusion if this is just an
adhesion separation issue resulting in blotches resembling mold, or
actual mold causing the separation. (Have we had some sort of cause
for this problem?)
Anyway, FYI for those interested. May be good for parts, although the
initial bid price is a quite high side given the condition.
-eric
P.S. I have no connection to the seller, am not pushing a purchase in any way.
17 Jul
17 Jul
2:34 a.m.
On Wed, 16 Jul 2008, Eric wrote:
Terminal Buffs and others interested:
I've seen screen rot before -- even owning one with perimeter
symptoms, but this is an example of _extreme_ "screen rot" (separation
of the protective plate from the CRT) on an ADM-3a.
See picture(s) --
Eww... That's a teeny bit worse than the rot on the ADM-3A I liquidated a
couple months ago. That one sold for $75, I think. This starting price
is way out of line.
--
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?
9:24 a.m.
Eric wrote:
Terminal Buffs and others interested:
I've seen screen rot before -- even owning one with perimeter
symptoms, but this is an example of _extreme_ "screen rot" (separation
of the protective plate from the CRT) on an ADM-3a.
That's about how bad the one on the HP-250 display was that I 'attacked'.
I'm unsure if we've ever come to the
conclusion if this is just an
adhesion separation issue resulting in blotches resembling mold, or
actual mold causing the separation. (Have we had some sort of cause
for this problem?)
I believe Sellam still has an offer open to analyse the decay if someone can
send him a sample - I'd already ditched the pile of rot from the HP-250 by
that point.
cheers
Jules
10:05 a.m.
--- On Thu, 7/17/08, Eric <eric940 at gmail.com> wrote:
I've seen screen rot before -- even owning one
with
perimeter
symptoms, but this is an example of _extreme_ "screen
rot" (separation
of the protective plate from the CRT) on an ADM-3a.
I had an ADM3A with bad rot like that, but I never tried to fix that one. The rest of the
terminal was in such terrible shape, it just got parted out. I've got a couple other
terminal tubes with light rot forming around the edges though.
I'm unsure if we've ever come to the
conclusion if
this is just an
adhesion separation issue resulting in blotches resembling
mold, or
actual mold causing the separation. (Have we had some sort
of cause
for this problem?)
I don't know about the terminal picture tubes, or how they're bonded, but I do
know that this problem also affects old color television picture tubes as well. The old
color tubes from the late 50's/60's will develop similar rot all along the edges,
sometimes all the way to the middle. It's referred to as "cataracts". I
don't know if it's mold, but it basically results in the breakdown of the PVA
bonding compound that holds the safety glass to the face of the tube. To remove it, at
least on the TV tubes, you take the the tube out of the set, put it neck down in a large
bucket/barrel so that it's supported, and use a heat gun to heat up the screen. After
a while, the PVA will soften, and the faceplate can be gently separated from the tube.
Don't pry it up - try to gently induce air bubbles under it with wooden shims and
heat. Once the bond breaks over most of the tube, the glass should come off without
breaking. Then you clean out all the PVA gunk, and
reattach the safety glass with packing tape along the edges.
I've never run across a terminal that was bad enough to warrent fixing (and where the
rest of the terminal was intact enough to bother with). Fortunately, the 12" mono
tubes in the ADM3 and the like are pretty easy to find, so replacement is usually an
option. Now, with the old color TV tubes, it's a different story. Try finding a
replacement 21FJP22! (It's a round, 21" color picture tube, 70 degree deflection
angle)
Note that on some color TV tubes (Zenith, IIRC), the bonding compound is different and
won't come off with a heat gun. Those tubes require "persuasion", in the
form of a car battery and nichrome wire. I have no idea what class of bonding compounds
the terminals fall under. But, if anyone has a badly delaminated tube, I would be
interested to hear how far you get with the heat gun.
-Ian
10:26 a.m.
On Thu, 17 Jul 2008, Mr Ian Primus wrote:
middle. It's referred to as "cataracts".
I don't know if it's mold, but
it basically results in the breakdown of the PVA bonding compound that
holds the safety glass to the face of the tube. To remove it, at least
on the TV tubes, you take the the tube out of the set, put it neck down
in a large bucket/barrel so that it's supported, and use a heat gun to
heat up the screen. After a while, the PVA will soften, and the
faceplate can be gently separated from the tube. Don't pry it up - try
to gently induce air bubbles under it with wooden shims and heat. Once
the bond breaks over most of the tube, the glass should come off without
breaking. Then you clean out all the PVA gunk, and reattach the safety
glass with packing tape along the edges.
I have a HP 2647A terminal with a severe case of screen rot which I
would like to refurbish:
http://sturgeon.css.psu.edu/~mloewen/Oldtech/Terminals/HP2647A-1L.jpg
http://sturgeon.css.psu.edu/~mloewen/Oldtech/Terminals/
Do you think this would be a candidate for the heat gun method, or
acetone around the edges of the shield as others have suggested?
Mike Loewen mloewen at cpumagic.scol.pa.us
Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/
11:37 a.m.
New subject: Extreme screen "rot" on a TEC terminal
On Thu, 17 Jul 2008, Mr Ian Primus wrote:
> middle. It's referred to as
"cataracts". I don't know if it's mold,
> but it basically results in the breakdown of the PVA bonding compound
> that holds the safety glass to the face of the tube. To remove it, at
> least on the TV tubes, you take the the tube out of the set, put it
> neck down in a large bucket/barrel so that it's supported, and use a
> heat gun to heat up the screen. After a while, the PVA will soften,
> and the faceplate can be gently separated from the tube. Don't pry it
> up - try to gently induce air bubbles under it with wooden shims and
> heat. Once the bond breaks over most of the tube, the glass should
> come off without breaking. Then you clean out all the PVA gunk, and
> reattach the safety glass with packing tape along the edges.
This sounds like
it might work. I just found an old TEC series 400
terminal that has a bad case of rot. I'll give the heat gun a try this
weekend.
I'll post what I find out. Here's a photo of the terminal's screen:
http://www.dvq.com/tek/or/tec_440_front.jpg
Thanks for the ideas,
Bob
11:50 a.m.
New subject: Extreme screen "rot" on a TEC terminal
>>>> "Bob" == Bob Rosenbloom
<bobalan at sbcglobal.net> writes:
Bob> On Thu, 17 Jul 2008, Mr Ian Primus wrote:
>> middle. It's referred to as
"cataracts". I don't know if it's
>> mold, but it basically results in the breakdown of the PVA
>> bonding compound that holds the safety glass to the face of the
>> tube. To remove it, at least on the TV tubes, you take the the
>> tube out of the set, put it neck down in a large bucket/barrel so
>> that it's supported, and use a heat gun to heat up the
>> screen. After a while, the PVA will soften, and the faceplate can
>> be gently separated from the tube. Don't pry it up - try to
>> gently induce air bubbles under it with wooden shims and
>> heat. Once the bond breaks over most of the tube, the glass
>> should come off without breaking. Then you clean out all the PVA
>> gunk, and reattach the safety glass with packing tape along the
>> edges.
Bob> This sounds like it might work. I just found an old TEC
series
Bob> 400 terminal that has a bad case of rot. I'll give the heat gun
Bob> a try this weekend.
Be sure to wear good quality protective gear (full face shield plus
safety glasses) in case the tube decides to blow up from thermal
stress.
paul
16 Jul
16 Jul
10:25 p.m.
New subject: Extreme screen "rot" on a TEC terminal
Be sure to wear good quality protective gear (full
face shield plus
safety glasses) in case the tube decides to blow up from thermal
stress.
As it says in my Whitechapel MG1 technical manual :
'All persons handling a CRT should be wearing the following items :
a) Gauntlets to protect the hands
b) A Class 1 British Standard BS2092 (impact resistant) face visor with
headband, to protect the face and eyes
c) Canvas apropn to protect those other preceious parts '
:-)
-tony
18 Jul
18 Jul
9:23 a.m.
New subject: Extreme screen "rot" on a TEC terminal
In article <487F6728.2030607 at sbcglobal.net>,
Bob Rosenbloom <bobalan at sbcglobal.net> writes:
Wow Bob, that's a new one for me. What year is it from?
--
"The Direct3D Graphics Pipeline" -- DirectX 9 draft available for download
<http://www.xmission.com/~legalize/book/download/index.html>
Legalize Adulthood! <http://blogs.xmission.com/legalize/>
[heat gun
approach]
This sounds like it might work. I just found an old TEC series 400
terminal that has a bad case of rot. I'll give the heat gun a try this
weekend.
I'll post what I find out. Here's a photo of the terminal's screen:
http://www.dvq.com/tek/or/tec_440_front.jpg
12:46 p.m.
New subject: TEC terminals - was:Re: Extreme screen "rot"
Richard wrote:
Wow Bob, that's a new one for me. What year is it
from?
The date on the manual is January 1973. One of the reasons I picked it
up is it came with them manual and a set
of schematics. It uses MOS shift registers for it's memory. The rest is
mostly 74xx series TTL.
I actually have three of these terminals. The other two are rack mount
ones that I've had for awhile.
They can be seen about 3/4 the way down on this page:
http://www.dvq.com/oldcomp/misc.htm
They display 24 lines of 80 or 72 characters and it appears to be upper
case only.
Bob
17 Jul
17 Jul
11:54 a.m.
On Thu, Jul 17, 2008 at 7:26 AM, Mike Loewen
<mloewen at cpumagic.scol.pa.us> wrote:
I have a HP 2647A terminal with a severe case of screen rot which I would
like to refurbish:
http://sturgeon.css.psu.edu/~mloewen/Oldtech/Terminals/HP2647A-1L.jpg
http://sturgeon.css.psu.edu/~mloewen/Oldtech/Terminals/
Do you think this would be a candidate for the heat gun method, or acetone
around the edges of the shield as others have suggested?
There is also the nichrome wire method which has been used on HP 264x
terminal CRTs:
http://www.classiccmp.org/pipermail/cctalk/2005-February/059554.html
2:25 p.m.
Mr Ian Primus wrote:
I don't know about the terminal picture tubes, or
how they're bonded, but I
do know that this problem also affects old color television picture tubes
as well. The old color tubes from the late 50's/60's will develop similar
rot all along the edges, sometimes all the way to the middle. It's referred
to as "cataracts".
Interesting; I've seen that often on old car windshields - it always seems to
be at the edges though and without "mould spots", whereas a terminal CRT seems
just as likely to develop patches anywhere on its surface.
I'm not sure if it's exactly the same breakdown process, or if the
'cataracts'
one requires an air ingress element, whilst the 'mould spots' doesn't...
Note that on some color TV tubes (Zenith, IIRC), the
bonding compound is
different and won't come off with a heat gun. Those tubes require
"persuasion", in the form of a car battery and nichrome wire.
That's the method I used for the HP-250 - it still took a little effort (the
PSU I had to hand was rather under-spec for the job) but went easily enough.
cheers
Jules
5826
days inactive
5827
days old
11 comments
10 participants
participants (10)
-
ard＠p850ug1.demon.co.uk -
bobalan＠sbcglobal.net -
dgriffi＠cs.csubak.edu -
eric940＠gmail.com -
glen.slick＠gmail.com -
ian_primus＠yahoo.com -
jules.richardson99＠gmail.com -
legalize＠xmission.com -
mloewen＠cpumagic.scol.pa.us -
Paul_Koning＠Dell.com