Museum report: terminals
Evan said:
Regarding the terminals: now that we pretty know * what * we have, the next step is to organize it all. Right now it's all in one aisle, but only a little organized by cart/shelf. There are some obscure terminals that we probably don't need, and not enough of what we probably do need. This job will be hard work due to the weight of TTYs and stuff.
Well, Evan asked me to come in on Sunday, to review the terminals and inventory them. That's because of my experience in the era of the 1970's and 80's. I was a minicomputer and mainframe site manager, and I was a technical student user at various universities; later I was a digital engineer. I also repair terminals. I'll walk though what I saw, and post a summary here to inform the people Evan is asking for help. I'll send Evan a more detailed report, but he has the list and location-of information I compiled Sunday. I did a quick survey (two hours), focused on CRT-based terminals and gave the list to Evan. Only warehoused terminals, not ones on display. Mostly there's DEC terminals. A dozen VR-201's (most with "moldy" CRTs). VR-201's are CRT "heads" which have a cabled keyboard, and often were used with DEC desktop computers. Also a few DEC VT-100 or VT-180; the 180's may have a microcomputer. A few DEC 200 or 400 series terminals. A few each, of ADM-3A, Heath H19 (Zenith Z19), a Perkin-Elmer model, an IBM model, a few other brand/models. There's a small number of one-each of ASCII based commodity terminals - this is what Evan called "obscure" I think. Hazeltine brand, ADDS, and so on. Evan has the list, he can provide details. Some of these have "moldy CRTs" too. Many terminals used detatched keyboards. There's boxes of keyboards, which I did not survey; so I don't know if there's enough or too many! And there's a few mechanical or printing terminals, which I did not survey but noted. I didn't cover monitors - I'll explain why that matters to terminals. I saw many "moldy" CRT's - that's when the front of the CRT has a transparent cover that's separating from the glass. Repair means replacing the CRT, which can take most of an hour depending. CRT's are available for tens of dollars for common types, some CRTs can be swapped around from microcomputer monitors, even old TV's. A number of tech volunteers are familiar with these repairs. Evan said "There are some obscure terminals that we probably don't need". I disagree, for several reasons. If they work, they are useful; if they don't the CRTs may be useful. It's a matter of history - lots of little companies made terminals, it's not all IBM, DEC, HP. Here's my experience, Evan - computer rooms in the era used lots of kinds of terminals. Also: to provide public visitors with a terminal they can bang on. And, terminals won't be EASIER to get in the future. But, it's ALSO true, there were computer-rooms with one kind of terminal. The HP, Perkin Elmer, IBM, DEC terminals I saw may go with specific minicomputers in the collection. The museum may need more of those. Only DEC VR201's seem to be in any quantity. Evan's focus on Sunday, was to identify and organize. I'm looking a little further ahead, to repair and potential uses. Now, with a list in hand, Evan can ask others to look over specific terminals for repair, to identify monitors as "CRT donors", to solicit CRT's for replacement. And to start looking to match minicomputers with terminals for display and use. And, to allocate terminals for various purposes, and to tell people what terminals we have or don't have. I'm describing my general results here in the list, so people with terminals or monitors, or skills, are better informed and can offer specific help or items. Herb Johnson -- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net preserve, recover, restore 1970's computing email: hjohnson AT retrotechnology DOT com or try later herbjohnson AT retrotechnology DOT info
On 7/9/2018 11:39 AM, Herb Johnson via vcf-midatlantic wrote:
I saw many "moldy" CRT's - that's when the front of the CRT has a transparent cover that's separating from the glass. Repair means replacing the CRT, which can take most of an hour depending. CRT's are available for tens of dollars for common types, some CRTs can be swapped around from microcomputer monitors, even old TV's. A number of tech volunteers are familiar with these repairs.
These CRT tubes don't have to be replaced, the CRTs can be very carefully heatgunned to remove the front protective glass cover and scrape out the 'cataract' goo. I think Ian has done it to a few of them already? -- Jonathan Gevaryahu jgevaryahu@gmail.com jgevaryahu@hotmail.com
On Mon, Jul 9, 2018 at 12:27 PM, Jonathan Gevaryahu via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> wrote:
On 7/9/2018 11:39 AM, Herb Johnson via vcf-midatlantic wrote:
I saw many "moldy" CRT's - that's when the front of the CRT has a transparent cover that's separating from the glass. Repair means replacing the CRT, which can take most of an hour depending.
AFAIK, it's bubbles in the PVA layer between the face of the CRT and the implosion protection screen.
These CRT tubes don't have to be replaced, the CRTs can be very carefully heatgunned to remove the front protective glass cover and scrape out the 'cataract' goo. I think Ian has done it to a few of them already?
I've done it with a VT220. You can use a heat gun or a hot wire to cut the PVA to free the shield from the tube, then it's all cleanup. You do need to re-install the shield because otherwise the CRT clamps don't fit really well and the tube slides around. I used dots of a thick (1mm?) silicone "tape" on the corners and it worked well. Just a small airgap in front of the face of the tube instead of a layer of what is supposed to be optically clear PVA. -ethan
On Mon, Jul 9, 2018 at 1:46 PM, Ethan Dicks <ethan.dicks@gmail.com> wrote:
I've done it with a VT220...
You do need to re-install the shield because otherwise the CRT clamps don't fit really well and the tube slides around. I used dots of a thick (1mm?) silicone "tape" on the corners and it worked well.
My buddy sent me the part number for the tape he gave me a strip of: 3M Scotch 4905 VHB tape, 1/2" wide, comes in a 15' roll. 20 mil/0.5mm thick. 3M Product Number 4905, 3M ID B40065643 https://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-VHB-Tape-4905/?N... (hopefully that's not a session id at the end of the URL. If it is, just search by product number and width). I used 1/2" squares at the corners and they are hidden behind the bezel. it's a bit thinner than the original PVA layer but the shield thickness is enough to let the CRT sit fine in the mountings and the 3M 4905 is quite flexible like the PVA. -ethan
Well, Evan asked me to come in on Sunday, to review the terminals and inventory them. That's because of my experience in the era of the 1970's and 80's. I was a minicomputer and mainframe site manager, and I was a technical student user at various universities; later I was a digital engineer. I also repair terminals. I'll walk though what I saw, and post a summary here to inform the people Evan is asking for help. I'll send Evan a more detailed report, but he has the list and location-of information I compiled Sunday.
I did a quick survey (two hours), focused on CRT-based terminals and gave the list to Evan. Only warehoused terminals, not ones on display. Mostly there's DEC terminals. A dozen VR-201's (most with "moldy" CRTs). VR-201's are CRT "heads" which have a cabled keyboard, and often were used with DEC desktop computers. Also a few DEC VT-100 or VT-180; the 180's may have a microcomputer. A few DEC 200 or 400 series terminals.
A few each, of ADM-3A, Heath H19 (Zenith Z19), a Perkin-Elmer model, an IBM model, a few other brand/models. There's a small number of one-each of ASCII based commodity terminals - this is what Evan called "obscure" I think. Hazeltine brand, ADDS, and so on. Evan has the list, he can provide details. Some of these have "moldy CRTs" too.
Many terminals used detatched keyboards. There's boxes of keyboards, which I did not survey; so I don't know if there's enough or too many! And there's a few mechanical or printing terminals, which I did not survey but noted. I didn't cover monitors - I'll explain why that matters to terminals.
I saw many "moldy" CRT's - that's when the front of the CRT has a transparent cover that's separating from the glass. Repair means replacing the CRT, which can take most of an hour depending. CRT's are available for tens of dollars for common types, some CRTs can be swapped around from microcomputer monitors, even old TV's. A number of tech volunteers are familiar with these repairs.
Evan said "There are some obscure terminals that we probably don't need". I disagree, for several reasons. If they work, they are useful; if they don't the CRTs may be useful. It's a matter of history - lots of little companies made terminals, it's not all IBM, DEC, HP. Here's my experience, Evan - computer rooms in the era used lots of kinds of terminals. Also: to provide public visitors with a terminal they can bang on. And, terminals won't be EASIER to get in the future.
But, it's ALSO true, there were computer-rooms with one kind of terminal. The HP, Perkin Elmer, IBM, DEC terminals I saw may go with specific minicomputers in the collection. The museum may need more of those. Only DEC VR201's seem to be in any quantity.
Evan's focus on Sunday, was to identify and organize. I'm looking a little further ahead, to repair and potential uses. Now, with a list in hand, Evan can ask others to look over specific terminals for repair, to identify monitors as "CRT donors", to solicit CRT's for replacement. And to start looking to match minicomputers with terminals for display and use. And, to allocate terminals for various purposes, and to tell people what terminals we have or don't have. I'm describing my general results here in the list, so people with terminals or monitors, or skills, are better informed and can offer specific help or items.
Herb Johnson
We definitely picked the right person for this job! Thanks again Herb for the detailed report you gave me yesterday.
On 7/9/2018 1:04 PM, Evan Koblentz wrote:
Well, Evan asked me to come in on Sunday, to review the terminals and inventory them. ...I'll send Evan a more detailed report, but he has the list and location-of information I compiled Sunday.
We definitely picked the right person for this job! Thanks again Herb for the detailed report you gave me yesterday.
To be clear, I gave Evan on Sunday a list of terminals and shelf locations. Today he got my detailed report by email, and my comments as posted here. Jonathan Gevaryahu wrote:
These CRT tubes don't have to be replaced, the CRTs can be very carefully heatgunned to remove the front protective glass cover and scrape out the 'cataract' goo. I think Ian has done it to a few of them already?
Ethan Dicks also described this process. Also here's where someone describe it to me: http://www.retrotechnology.com/restore/adm3a_nick.html I'll be blunt to be brief. A heatgun on a messy, gooey, HOT, CRT is too dangerous and takes too long, in my opinion. I won't do it. Ian and others may do such things. "There are old pilots, there are bold pilots, but there aren't many old, bold pilots." Private email to me:
Hey Herb: where can one get replacement CRTs for "tens of dollars"? I'm looking to repair an H19 that is otherwise in good shape but the CRT seems to be bad. Tx.
Rebuilt CRT's for common CRT's say 12-inch, seem to be under $100, maybe well under. Try https://cathoderaytubes.com Used CRT's, say salvaged from other computers, are less. About "bad", you weren't specific. Heath H89's and H19's use the same CRT. (Zenith Z89, Z19), so look for another unit. I have extra Heath CRT's, I'll get back to ya on that. But the common problem with those models, is poor contact at the CRT socket and pins for the high-current filament. See if the filament is "lit", if not see if wriggling the socket changes your results. YOu can tell me privately about other CRT problems. Herb "Cathode Ray" Johnson -- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net preserve, recover, restore 1970's computing email: hjohnson AT retrotechnology DOT com or try later herbjohnson AT retrotechnology DOT info
If you don't like the idea of heat gunning a tube, there are other methods: I've seen them floated off over an extended period in room-temperature water, or heated by placing face-up in the sun with a black trash bag over the front. I've done the heat gun method, you don't need to get it crazy hot, and in my experience the PVA layer pretty much peels off, if you do it right. It leaves slimy residue on the safety glass and the tube, but this comes off with alcohol. I stuck my CRTs in a 5-gallon bucket and only heated the face of it. It would've been uncomfortable to hold the safety glass, but not so hot as to burn you. Thanks, Jonathan On Mon, Jul 9, 2018 at 2:23 PM, Herb Johnson via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
On 7/9/2018 1:04 PM, Evan Koblentz wrote:
Well, Evan asked me to come in on Sunday, to review the terminals and
inventory them. ...I'll send Evan a more detailed report, but he has the list and location-of information I compiled Sunday.
We definitely picked the right person for this job! Thanks again Herb for the detailed report you gave me yesterday.
To be clear, I gave Evan on Sunday a list of terminals and shelf locations. Today he got my detailed report by email, and my comments as posted here.
Jonathan Gevaryahu wrote:
These CRT tubes don't have to be replaced, the CRTs can be very carefully
heatgunned to remove the front protective glass cover and scrape out the 'cataract' goo. I think Ian has done it to a few of them already?
Ethan Dicks also described this process. Also here's where someone describe it to me:
http://www.retrotechnology.com/restore/adm3a_nick.html
I'll be blunt to be brief. A heatgun on a messy, gooey, HOT, CRT is too dangerous and takes too long, in my opinion. I won't do it. Ian and others may do such things. "There are old pilots, there are bold pilots, but there aren't many old, bold pilots."
Private email to me:
Hey Herb: where can one get replacement CRTs for "tens of dollars"?
I'm looking to repair an H19 that is otherwise in good shape but the CRT seems to be bad. Tx.
Rebuilt CRT's for common CRT's say 12-inch, seem to be under $100, maybe well under. Try
Used CRT's, say salvaged from other computers, are less. About "bad", you weren't specific. Heath H89's and H19's use the same CRT. (Zenith Z89, Z19), so look for another unit. I have extra Heath CRT's, I'll get back to ya on that.
But the common problem with those models, is poor contact at the CRT socket and pins for the high-current filament. See if the filament is "lit", if not see if wriggling the socket changes your results. YOu can tell me privately about other CRT problems.
Herb "Cathode Ray" Johnson
-- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net preserve, recover, restore 1970's computing email: hjohnson AT retrotechnology DOT com or try later herbjohnson AT retrotechnology DOT info
On 7/9/2018 2:35 PM, systems_glitch via vcf-midatlantic wrote:
If you don't like the idea of heat gunning a tube, there are other methods: I've seen them floated off over an extended period in room-temperature water, or heated by placing face-up in the sun with a black trash bag over the front.
I've done the heat gun method, you don't need to get it crazy hot, and in my experience the PVA layer pretty much peels off, if you do it right. It leaves slimy residue on the safety glass and the tube, but this comes off with alcohol. I stuck my CRTs in a 5-gallon bucket and only heated the face of it. It would've been uncomfortable to hold the safety glass, but not so hot as to burn you.
Thanks, Jonathan
On Mon, Jul 9, 2018 at 2:23 PM, Herb Johnson via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
Pardons if this gets posted twice, I did not get notification of the first one being received by the message board system. I heated the tube with a work light. I think Ian suggested this to me. About 20 minutes or so? Not sure. Monitored progress with a thermometer. Here's my pics. https://imgur.com/a/eS4ybZo
Amazing restoration job. Congratulations!
-----Original Message----- From: vcf-midatlantic <vcf-midatlantic-bounces@lists.vcfed.org> On Behalf Of Douglas Crawford via vcf-midatlantic Sent: Monday, July 09, 2018 9:50 PM To: vcf-midatlantic@lists.vcfed.org Cc: Douglas Crawford <touchetek@gmail.com> Subject: Re: [vcf-midatlantic] Museum report: terminals
On 7/9/2018 2:35 PM, systems_glitch via vcf-midatlantic wrote:
If you don't like the idea of heat gunning a tube, there are other methods: I've seen them floated off over an extended period in room-temperature water, or heated by placing face-up in the sun with a black trash bag over the front.
I've done the heat gun method, you don't need to get it crazy hot, and in my experience the PVA layer pretty much peels off, if you do it right. It leaves slimy residue on the safety glass and the tube, but this comes off with alcohol. I stuck my CRTs in a 5-gallon bucket and only heated the face of it. It would've been uncomfortable to hold the safety glass, but not so hot as to burn you.
Thanks, Jonathan
On Mon, Jul 9, 2018 at 2:23 PM, Herb Johnson via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
Pardons if this gets posted twice, I did not get notification of the first one being received by the message board system. I heated the tube with a work light. I think Ian suggested this to me. About 20 minutes or so? Not sure. Monitored progress with a thermometer. Here's my pics. https://imgur.com/a/eS4ybZo
This is a great thread. VCF has several terminals that need this service. Ian (and anyone else who's interested), how about we fix as many as possible at the August workshop? On Mon, Jul 9, 2018, 10:04 PM Glenn Roberts via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
Amazing restoration job. Congratulations!
-----Original Message----- From: vcf-midatlantic <vcf-midatlantic-bounces@lists.vcfed.org> On Behalf Of Douglas Crawford via vcf-midatlantic Sent: Monday, July 09, 2018 9:50 PM To: vcf-midatlantic@lists.vcfed.org Cc: Douglas Crawford <touchetek@gmail.com> Subject: Re: [vcf-midatlantic] Museum report: terminals
On 7/9/2018 2:35 PM, systems_glitch via vcf-midatlantic wrote:
If you don't like the idea of heat gunning a tube, there are other methods: I've seen them floated off over an extended period in room-temperature water, or heated by placing face-up in the sun with a black trash bag over the front.
I've done the heat gun method, you don't need to get it crazy hot, and in my experience the PVA layer pretty much peels off, if you do it right. It leaves slimy residue on the safety glass and the tube, but this comes off with alcohol. I stuck my CRTs in a 5-gallon bucket and only heated the face of it. It would've been uncomfortable to hold the safety glass, but not so hot as to burn you.
Thanks, Jonathan
On Mon, Jul 9, 2018 at 2:23 PM, Herb Johnson via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
Pardons if this gets posted twice, I did not get notification of the first one being received by the message board system. I heated the tube with a work light. I think Ian suggested this to me. About 20 minutes or so? Not sure. Monitored progress with a thermometer. Here's my pics. https://imgur.com/a/eS4ybZo
On Mon, Jul 9, 2018 at 2:23 PM, Herb Johnson via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> wrote:
I'll be blunt to be brief. A heatgun on a messy, gooey, HOT, CRT is too dangerous and takes too long, in my opinion. I won't do it. Ian and others may do such things. "There are old pilots, there are bold pilots, but there aren't many old, bold pilots."
I am not endorsing the heat gun method. I did my one cold, by using a wire as a "saw" to cut through the PVA. I have heard that using a nichrome wire cuts through it like butter but that's not what I did. It took time and it left a fair mess to clean up with plastic scrapers and alcohol. I was only doing one so I wasn't trying to optimize the process. I was working slow and careful and it all came out fine. It comes down to time/effort vs value of return. I would almost certainly choose another approach if I had a gaylord of terminals to process. -ethan
On 7/9/2018 2:58 PM, Ethan Dicks via vcf-midatlantic wrote:
On Mon, Jul 9, 2018 at 2:23 PM, Herb Johnson via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> wrote:
I'll be blunt to be brief. A heatgun on a messy, gooey, HOT, CRT is too dangerous and takes too long, in my opinion. I won't do it. Ian and others may do such things. "There are old pilots, there are bold pilots, but there aren't many old, bold pilots." I am not endorsing the heat gun method. I did my one cold, by using a wire as a "saw" to cut through the PVA. I have heard that using a nichrome wire cuts through it like butter but that's not what I did. It took time and it left a fair mess to clean up with plastic scrapers and alcohol. I was only doing one so I wasn't trying to optimize the process. I was working slow and careful and it all came out fine.
It comes down to time/effort vs value of return. I would almost certainly choose another approach if I had a gaylord of terminals to process.
-ethan
Ah that reminded me to post my pics of the VR201 restoration from VCFEast, the monitor used in our exhibit. I used the work light method on two monitors. https://imgur.com/a/eS4ybZo
systems_glitch:
I've seen them floated off over an extended period in room-temperature water, or heated by placing face-up in the sun with a black trash bag over the front.
Ethan Dicks:
I did my one cold, by using a wire as a "saw" to cut through the PVA.
(gasp) I've just been schooled! ;) Thanks to my friends for these more temperate suggestions. Of course, make sure that CRT is working and displays bright before investing this much work. - Herb -- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net
There are definitely many methods to use - an important consideration is the type of PVA. There are two basic types. One that gets cloudy and mold spots in it - that one is susceptible to the heat gun or, if you're patient, potentially broken down with water. The water method can take a month to work, from the reports I've heard. The other type turns green and develops fringing and darkening in the material. That type cannot be heat gunned off, it must be cut with a hot wire. It is also impervious to the water. Personally, I've done a fair number of tubes, using mostly the heat gun method, on both small and large tubes. I've found it to work quite well, and I've never had a tube implode. The hot wire method has it's merits (and is required in some cases). I've never personally tried the water method, I'm just too impatient. -Ian On Mon, Jul 9, 2018 at 6:54 PM, Herb Johnson via vcf-midatlantic <vcf-midatlantic@lists.vcfed.org> wrote:
systems_glitch:
I've seen them floated off over an extended period in room-temperature water, or heated by placing face-up in the sun with a black trash bag over the front.
Ethan Dicks:
I did my one cold, by using a wire as a "saw" to cut through the PVA.
(gasp) I've just been schooled! ;) Thanks to my friends for these more temperate suggestions. Of course, make sure that CRT is working and displays bright before investing this much work. - Herb
-- Herbert R. Johnson, New Jersey in the USA http://www.retrotechnology.com OR .net
participants (8)
-
Douglas Crawford -
Ethan Dicks -
Evan Koblentz -
Glenn Roberts -
Herb Johnson -
Ian Primus -
Jonathan Gevaryahu -
systems_glitch