Repairing a Bad Case of Cataracts on an ADM-3A Terminal
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- čas přidán 9. 06. 2024
- About two years ago, I traded an ADDS Viewpoint terminal for this gorgeous AMD-3A that needed a little bit of love. This summer has been one of the hottest on record, so what better time to tackle a cataracts repair than now! With the help of the blazing hot Texan sun, and a little bit of elbow grease, we get this ADM-3A terminal looking nearly brand new once again.
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Intro Music adapted from:
Artist: The Runaway Five
Title: The Shinra Shuffle
ocremix.org/remix/OCR01847
Thanks for watching!
Chapters
0:00 What are we doing today Brain?
3:13 Disassembly
4:31 Cleaning
7:24 A brief look at terminal history
8:58 A brief look at the ADM-3A
11:02 Cataracts repair
12:44 First (anti-climactic) start up
14:50 Second start up and testing
17:11 Quick repair and more testing
19:36 Hooked up to the Centurion
21:01 That went way smoother than I was expecting
22:13 Koma-san - Věda a technologie
“It will give us an error hopefully.“, (c) usagi 2023.
"Task failed succesfully."
And further progress is getting a different error message.
Lol, I've been there. Sometimes any output at all is a win.
I like how the Centurion has gone from a pile'o'bits to become the reference machine to test all the new projects with.
A couple of cautions about cataracts - different manufacturers used different glues, so not all removals will be this easy. Also, prying and stressing a CRT in the wrong place can lead to implosion, so be careful! Lastly, I'd suggest re-sealing the edge of the re-installed cover all around with tape or even silicone. The static of a CRT will pull dust and dirt into any opening, then you've got debris between the CRT and shield again.
Shango066 uses silicone around the edges, leaving no gaps. Offhand I forget which brand/type he recommends.
Ah there’s the know it all boomer who thinks no one else knows anything. It’s not a proper comment section with out you. Thanks 😀
It’s pretty obvious he knows what he’s doing, he didn’t use the wire throughout, didn’t use a metal screwdriver but a bondo spatula which is plastic, flexible, and soft just in case you didn’t know I thought I’d mention that. (See degrading and disrespectful right?). You can also tell by his confidence, and knowing exactly what to do without explaining how he knows this that he’s probably done this more times then you. So sit down.
Lastly I’d suggest closing your mouth for a change. You got a few comments on this channel going “um excuse me retard… you know…” This is likely the one of few time it will ever be turned on again, it doesn’t matter if it’s “done right” when even your way is a hack and also not “done right” just in case you didn’t know the whole thing was glued for a reason and for shock resistance. Anything just around the edges “makes this potentially dangerous”. Just so you know 😉 anything hitting that shield hard enough will crash it into the CRT and potentially cause it to go boom. Just so you know. Oh but that’s right it’s going to be a “museum” piece so none of that really matters. Dummy
In short: your advice wassnt asked for, needed, or required. What’s up with all you old people that know everything and can’t wait to force it down everyone’s necks? It’s a dislike able trait. I can imagine you now at Christmas dinner ranting and babbling as no one pays you any attention and just goes “uh huh” “uh huh” “oh yeah..” “that’s cool”
@@KameraShy He also uses small bits of wood to more gently and slowly pry the shield from the tube, and lets it sit while he is away from it in case of an implosion.
bugs (e.g. small thrips) can get in there too. All gaps should be sealed.
10:05 14 RAM chips is 2 kilowords of 7-bit memory. ASCII only needs 7 bits to represent upper- and lower-case letters, numbers and control codes. 24 rows of 80 characters is 1920 in total.
As a side note: The standard memory configuration was only 2K x 6 bits wide and the terminal came with 12 RAM chips. Two additional RAM chips and the character generator ROM gave the upgrade to display lower case.
@@Peter_S_ Different times, eh? You want lower-case characters? Need a hardware upgrade for that schmanciness!
The second row of RAM was actually optional. The super-cheap version only displayed every other line of text. Apparently that was a thing before 24x80 became the standard size for terminals.
Well, William Lear was no stranger to operating in wildly different markets!
Besides making jet planes and data terminals, he also created the 8-track audio tape system that once was popular in the USA.
Thanks! When he mentioned Lear, I was like "wait, there was something else completely unrelated that Lear was involved in", but for the life of me, I couldn't remember what it was. You nailed it!
Bill Lear grew up in Hannibal-Quincy area, at beginning of Radio Age (not far from where I grew-up).
He moved to Chicago and became acquainted with Gavin -
and became one of co-founders of Motorola.
He migrated to Wichita (near my Dad’s family 1880s homestead), entered Airplane mfg.
In early 1960s, he created the 8-track tape format for automotive industry.
The Lear-Seigler was split-offs of business units in early 1970s.
Person or company?
The Design Concept of these terminals were way ahead of their time, kind of like futuristic space age technology. Not only were they smart looking but they were also made to be very serviceable. Tremendous Job, well done!
10:02 - RAM size - 24x80 = 1920 characters, 14 RAM chips is 2 banks of 1Kx7 bits per character=2048
If you bought the budget version, it came without 2 of the RAM chips and the lowercase character ROM. Memory in that case was 2048 x 6 bits.
@@Peter_S_ The budget-budget version only had 6 RAM chips, and displayed every other line of text. I'm going to guess it's rare to find a 12-line version in the wild, since it's so easy to add the rest of RAM and set the right DIP switch.
Great job! You lucked out finding that missing chip. And the screen looks absolutely beautiful now! I don't even see any burn-in on it.
Thanks!
I should have gotten on the restore a little sooner so we could have had it up and going for your video! Though, your video was the inspiration I needed to get to work on it, haha.
Caught you here A bigg helllo from PCBWayyyyy
@@PCBWay I ❤ PCBWayyyyyy!
Just as an FYI, back in the day (early eighties) we did a lot of development work and would need to change the baud rate, # of bits, etc., very often. So we just used a clear tape hinge up top of the DIP switch cover so we would not have to unscrew and re-screw the cover ALL. THE. TIME. Not elegant but functional. The previous owner may have had the same problem and just chucked the cover.
At my school, people just snapped the plates off.
Wow! The inside looked amazing after cleaning, you weren't kidding when you said brand new.
Yeah, I was a little blown away at how well the inside cleaned up!
The chips in the ADM 3A you identify as ROM are the character generator ROMs. The chip closest to the edge is a 2513 CGR-001 which was also used in the Apple 1 and Apple ][ through the rev. 4 motherboard. This contains 64 uppercase ASCII characters. The CGR-002 next to it contains the lowercase letters and a set of special characters (including the characters to display sexadecimal values).
Oh, wow, that's really interesting that the same ROM was used on the Apple 1 and ][ motherboards! Although, with the Apple being 40 columns (I think, it's been a while since I've seen an Apple II in person), it would have taken me a little bit to make the connection that the fonts are the same.
@@UsagiElectric There was also a CM8400 version of the 2513 which contained 64 Katakana characters.
The original full part number of the CGR-001 was the 2513CM2140 from Signetics circa 1970 and it features the 1967 version of ASCII. You have a General Instruments 2nd source for LSI with the CGR-001 part but the data is identical. The lowercase chip is house numbered with an LSI part number of 129323-02 CGR-002 and that is a VERY rare chip. I've never seen a dump of it (before a few minutes ago) and I've never seen one in the wild without it sitting next to a CGR-001. It appears to be a semi-clone of the Signetics 2513CM3021 which actually doesn't contain a 2nd copy of the punctuation but instead includes a new set of glyphs including an underlined U, V, W, X, Y, and Z to display sexidecimal numbers (See Dave Plummer's vid on sexidecimal).
I have a vague memory of the underlined W, X, Y, etc. on a screen but I don't recall the terminal I last saw them on; possibly a Hazeltine 1510 or a Televideo 950.
When Apple switched motherboard designs to remove the 4K DRAM addressing they also replaced the PMOS 2513CM2140 with a copy of the same data in an NMOS 2316 mask ROM, now with an Apple part number and supporting 128 (or 256?), 7 pixel wide glyphs. The uppercase is identical to Apple's font on the unenhance //e and before, but the lowercase is completely different.
@@Peter_S_ I can't seem to find the Dave's Garage video you mentioned. Do you remember the name?
@@joe--cool Yes, the video is from about a year ago and it's called "HAL 9000 and the Sexadecimal Mystery - Finally Explained!"
Sorry, I should have named it in the original post.
@@Peter_S_ Cool thanks a lot. The title seems to make it hard to find. Dumb algorithms.😄
Nice video about this great terminal. Back in the days when I was a student our university had rooms filled with these adm3a's which we called 'eitjes' in dutch (translates to 'little eggs'). The faculty board selected this model because they were the only ones that were 'student proof'. You could literally sit (or stand) on top of them, without breaking them. I spend years using them every day, hooked up to our pdp11 systems and IBM370 mainframe. Those where the days!
They became popular because they were also offered in kit form ($995) vs assembled ($1195). I built one for the Byte Shop in Raleigh NC (1974-5), and only missed one solder joint!
Oh, wow as a kit!? I would have loved that. Pray tell, what year was this?
For the cataract, my suggestion is first to use a body protection suit and an eye protection mask. The square CRTs in some cases don't react well if their bonding agent is removed. When reassemble the protection glass don't use the tape but silicone, so the dust don't go between the glass :)
Instead of silicone I'd recommend optical bonding adhesive. That will remove all reflections on the glass - air - glass transitions.
Tape is good for spacing.
A face mask and lab coat should suffice.
Whatever you use to replace the original goo still needs to be about 2mm thick so that the curvature matches. Sticky foam happens to be just right, and a lot less messy than trying to put more goo in there.
As for the strength of the glass, this is specifically for implosion protection (which is why you want to put it back!), so it's not going to suddenly explode on you.
OCA isn't magic, it works because it has the same refractive index as the glass it is bonded to. It's not going to be right for high-lead CRT glass and plastic, even if the shield was the right shape for it to attach directly...
Ohhh, that's really cool. I love the shape of it. The way the CRT housing slopes down in the back, it's so atomic age it hurts. Love seeing your uploads!
Sexiest. Terminal. Ever.
4:22 I don't know if anyone already mentioned it but the "integral implosion protection" refers to the metal band around the CRT, not the glass screen and the mouldy glue.
By the way that sticky tape that you used, will probably get brittle over time and because you didn't close off the space hermetically, there will eventually be dust between the glass and the tube.
That glass plate is designed to block shrapnel if the front of the CRT breaks during implosion. It is made of much better glass than is possible with CRT glass.
@@8bitwiz_ Glue on shields are surprisingly ineffective really. The integral implosion protection refers to the metal tension band, as in it's an integral part of the assembly unlike the glue on shield. It's intended to make it more difficult for the tube to spontaneously collapse from the front, the weakest part. If you don't believe me refer to literally any CRT TV service manual. CRTs are remarkably abuse tolerant because of that tension band.
You can see the difference between a CRT without a glue on shield and those with. Note, a glue on shield, not integral ceramic panels. Either way it goes if you are right beside it when it goes off your day just got a whole lot worse. It's not just big chunks moving around, it's all the glass powder. Breathe that in and you have a considerable problem and will need hospital attention. It's not pretty.
I saw quite a few ADM-3's attached to Altairs and IMSAIs in the late 1970's and early 1980's. Not a single one of them had the cover over the dip switches!
Lear invented the cartridge player for cars, too. Which became 8-Track cartridges.. 👍
I’n my 2nd year at my uni (1988) I joined the IT staff and got this very ADM3A on my desk, hooked up to a Sun 3/50. It was … ok … but a bit lacking in controls for Emacs. I vaguely recall programs using it had to use a trick to write the very last char on the screen without scrolling: write it to the penultimate position, back up, write an insert char to move it into place.
Despite its limitation and lack of speed, I did appreciate two things that made me use longer than you would expect: it was SILENT (fanless) and it took up little space on my desk, compared to a Sun 3. (I have a soft spot for this and would love to get my hands on one)
Wow we're almost the same age! I went to UNLV back in 1989 & the library had rows of terminals, most of them ADM3a! They weren't as fun to type on but I didn't know the history at the time. The back end, through a network terminal server, was a hopelessly overloaded (during the day anyway) MicroVAX-2 which would slow to a crawl with 3 simultaneous compilations. Laid my eyes on it once on a data center tour.
I bought from my high school a couple years back a truly rare terminal, a Liberty Freedom 100, that I used in my dorm room with a modem while there besides usual BBS duty. I want to say there was a termcap for it on the VAX but don't remember. It didn't have many emulations def not VTs. Fortunately Linux does but I no longer own it.
I think that must have been a different terminal. The Adm-3A doesn't have an insert-character functionality. That it could move the cursor to random places on the screen was already quite advanced :)
@@rhialtothemarvellify Apparently so! Thanks. For the record, the best information about the Adm 3A I could find was here which of course agree with you: www.bitsavers.org/pdf/learSiegler/ADM_3/DP2880486F_ADM3A_UM_Apr86.pdf
Oh, Dave you are seriously producing some amazing results here...both with this terminal AND with this video! A double bonus! So cool! Makes me proud to know you... 😉😉
Thanks so much man!
With our powers combined, we're keeping these weird old machines alive, one by one!
I'm surprised you didn't use the Shango066 method of de-cataracting. He also uses the heat of the day, but is a lot more careful with the extraction of the glue, resorting to wire knife in order to not put pressure on the CRT. After cleanup, he uses a silicone based adhesive to remarry the lens to the CRT, only with a single bead on the outside edge of the CRT.
He does it on large 1950s CRTs with no anti-implosion band and possibly a different glue formulation. This one was a much safer job, but not sealing the corners is still a blunder.
I did mine this way a few years ago, except I was being careful and only nibbled away a little at a time with a hook-end tool. That spatula thing did it much faster. But yes, the big difference is that this is a much smaller screen, so no need for a heat gun. And the edges do need to be sealed to keep dust from getting in. I used clear packing tape on mine, no need to be perfect because the lid hides so much of the CRT edge.
I left school at 16 but my learnings back then of 74series TTL and 4000 cmos still stands me in today with restoring old equipment.. :)
Back in the day to test these, we would use the rs232 serial loop back, as you did. Then type a [ U ] and an [ * ] (asterisk) would give you a data stream of 01010101 or 10101010, therefore one could check all data lines to make sure everything was working correctly, This method will find bad RAM memory bits also.
The fact that the screen doesn't clear brings you right into the wonderful world of TERMCAP files. The Centrurion must have something like that, too.
In the 80s, we had a PRIME minicomuter system that used these terminals at our college. Lovely keyboards and bright, clear green phosphor screens. About 2 years later I went for a job interview at the same college, and saw all these monitors outside just thrown in a dumpster/skip. If only I had been able to save at least one!
Living in Houston and also suffering this unbearable heat, I'm glad at least one good thing has come from this misery
I think the implosion protection is the metal implosion band around the cap of the CRT, not the glue or shield (I worked in a CRT factory in my late teens). The implosion band helps to keep the screen from flexing and when the CRT does shatter, it helps to contain the energy imparted through the glass. When CRT's impose without the band, glass goes flying everywhere - at 3am on midnight shift, an implosion will wake you up in a hurry.
I cannot believe how *mint* this 3A turned out! Separating the front "shield" from the CRT was particularly satisfying to watch. I am interested to see how you tackle the missing key caps and DIP-switch covers. Truly this is a magnificent data terminal. Gorgeous.
Brings back a lot of memories. I used one in the early 80’s for assembly language programming for many years. Thanks for the trip back in time.
That was really cool and the bunny flop at the end was adorable. Thanks!
I love it when they flop like this, it's the most adorable expression of being happy and relaxed!
Small correction: The Lear Siegler corporation predates the Learjet corporation and was completely separate. Bill Lear had no connection with Lear Siegler past 1961 and started the Learjet corporation in 1962. Further, Lear Siegler only started making terminals in 1972. And Bill Lear had sold Learjet in 1967.
As a serial entrepreneur Bill Lear was unique in the variety of areas of interest and invention. But he rarely stayed involved once a business idea was established.
Another fun fact about Lear-Siegler is a lot of the upgrade seats in GM products from the 80's and early 90's were produced by them. So the 12 way and such seats with the fancy lumbar.
Brings back memories. I worked at Lear Ziegler in the late 1970s. I tested ADM-1, ADM-2, and ADM-3As.
8:16 That is a KSR33 (no tape reader/punch) and it is the model used as ICL operators' terminals from the 1900 series, including volume knob to listen to the processor being stuck in a loop 😁 Actually, we used to be able to tell when the highways department were running an illicit number intensive job from their MOP terminal, which interfered with payroll and creditor processing until they finally stumped up and paid for a floating point unit and an extra 32K of core! Happy days.
you really should have worn a face shield and long sleeved jacket when working on removing the protective glass. If the screen imploded you'd be showered in glass bits.
Woah, I didn’t know CRT’s with that damage could be fixed, great video!
There have been videos on how to do that on CZcams for years. You must not have been looking very hard. I have to warn you though. He had an easy one. Some are really stubborn and he should have worn eye protection.
Thanks!
Initially I thought this type of CRT problem was un-saveable too, but it turns out, the hot Texan sun was the trick all along, haha.
Shango066 has done several of these operations on old TV's I think..
Yep, Shango066 has done a lot of these. And blistering southern heat and A LOT of patience is the key
@@UsagiElectric CRT Cataract problem? Shango066 to the rescue!! Complete with "Shango-isms". Hahaha!!
The ram was probably organized as 2k x 7 bits. No need to use 8 bits to store ascii characters.
Yes 24 rows x 80 characters is 1920
I used one of those when I was in school in the 70's. It was great. It replaced a Teletype terminal that was slow and noisy. We still had to run a paper tape to load code. We used a HP2100 computer.
Don't worry about the missing DIP switch cover. Most of the terminals at my school (in 1987) were missing it, most usually because people tinkered with the duplex settings. It was fun when people used ballpoint pens, or worse, pencils to set the switches!
11:28 this is so satisfying there should be entire channels of this
I used to sit around in the university library in my hometown, in the early 90s, playing DikuMUD on an engineering student's Apollo Domain 2500 that he somehow managed to get hooked up in the data center, via an ADDS Viewpoint 3A+. At the time, the library's "computer lab" was entirely populated with ADDS terminals hooked up to a concentrator via Gandalf connections.
Glad to see you finally got to work on this, and glad to hear that my "Texas sun" suggestion back at VCFSW worked for you! Funny about the UART chip hiding like that, but at least you have your lowercase ROM. I had to make an EPROM adapter board because mine was missing. Also my lid doesn't have those retaining ring thingies, the hinge rods are part of the lid and it just slides off sideways. All your chips are socketed, so I think yours is an earlier design. My case is brown, while you have what I think is the better blue color.
And I'm glad mine wasn't anywhere near that dirty and had all the key caps! But I did have to swap a few keyboard plungers (the hollow square that goes up and down) from a junk keyboard because the corners were splitting. As for the glass, I didn't use as much sticky foam, you did a much better job. Seeing that raster is a wonderful thing, because you know that all the analog stuff is working! The good side of that shorter brightness pot is that it doesn't stick out where it can get bumped.
EDIT: you might want to seal the edges of the CRT glass by wrapping clear packing tape around the edges. That keeps dust from getting in through the gaps of your foam. The screen frame has a surprising amount of overlap, so you can be sloppy by at least half an inch without it showing.
You don't really need that 2-3 jumper to do local mode, there's a dip switch for that in there somewhere. (Also don't use a pencil to flip the switches, it actually says so in the manual!)
The SRAM is 7 bits wide, with the second row being the difference between the 12 line version and the 24 line version, and the 7th bit for the lower case option. It's more obvious when most of the chips aren't socketed, and unlike yours, mine only has sockets for the big chips and 8/14 of the SRAM.
And speaking of lowercase, you need to get yours showing some! The ADM-3A lowercase font is a bit unusual and distinctive, it sticks up by a scan line to give more room for descenders.
What is it with the UART chips that they liked to go walkabout?
Makes me so happy to see this tech history get brought back to life!
So good, made me so happy, brings back some amazing memories of being an engineer 40 years ago
this really loosened my glue
8:54 - Someone was allowed to really flex their industrial design degree on this one.
A fantastic restoration of a beautifully designed device. They really put some thought into making it serviceable.
"Asbestos a can", eh? Nicely cleaned. Winner winner, chicken dinner :)
My goodness, 43 friggin' degrees? That's wireless energy transfer from a fusion reactor after all ;)
Nice design. I couldn't afford an ADM-3A terminal. So I bought a Heathkit H9 terminal and assembled it. It had 7 circuit boards: power supply circuit board, keyboard circuit board, RAM and counter circuit board, input/output circuit board, character generator circuit board, timing and processing unit circuit board, and video circuit board.
Am I the only one feeling warm fuzzies while watching these machines get a new lease on life instead of rotting in a dump?
Shango does a lot of cataract repairs, as he does a lot of older tube TV's. He usually uses a silicon around the edge to completely seal it as if there is any gap, like corners with double sided tape, it can allow dust to get in and I can imagine dust between the CRT and the shield would likely be really annoying.
Looks like you have a bit more work to do on this terminal to just get it 100%, but I think finding the missing key may be a the hardest thing of this., but it really is fantastic to see it up and running. If I recall this could be even sharper than how you have it with a little tweek of the focus. Going on memory, I think these had a very sharply focused CRT.
Maybe it could have been sharper but I could see the gaps between the scanlines.
Awesome to see those cataracts fixed! Great job!
Thanks! And thanks for the hook up!
Let me know when that ADDS terminal comes up, I'd love to see its white phosphor displaying text in 80 column glory too!
Nice work. Might be worth closing the air path into the cavity between crt and front glass : this will stop it filling up with new dust and grime (as it will probably tend to with the influence of the high voltage)
I love it when the item you're working on gives back the missing parts. I've had two recently purchased wind-up phonographs cough up missing parts that would have been a pain to find. I don't even ask how it got there, I just thank the part for showing up again so it can get back to work! (I have radios older than that Bendix computer. Wait: I think one of my tube radios IS a Bendix!)
I remember using a Tektronix storage-screen terminal (I think it was a 4014) during my PhD. I used it because I nobody else wanted to. This was in 1991, so it really was a relic of a bygone age at the time.
@shango066 Has done many excellent videos on cataracts. Safety is super important. Flying glass is no joke.
Finally a good use for all this Texas heat! Well done.
When I worked for Dictaphone, we had a dictation management system that was built around the Intel SBC 80/20 and there were two ADM-3A terminals. They had a dark grey base and a light grey top, but I forget where the Disctaphone logo was placed. I loved those terminals. Wish I had one now.....
You took me back to fall '76, when I first met my school's new Altair 8800a computers, one on an ASR33 and the other on an ADM3A. Cool!
I was really excited seeing this terminal come to life. It's amazing how the terminal works without a CPU and only utilizes TTL logic. Video terminals played a big part in my early tech days. I worked for Visual Technology, as I mentioned before, building, testing, and eventually repairing various models as well as their PC-like equipment and later the Ontel Corp terminals and systems.
The keyboard switches look familiar. I think they may also be used on some of the early Atari computers, not the later 800 X/L which was made with far less quality.
The keyboard switches are the old Stackpole type with the copper fingers. They were used on TRS-80 Model I (early versions), Atari 800, and TI 99/4A.
@@8bitwiz_ Thanks. That's what I thought because I had an old Atari 800 and they looked familiar. I also remember seeing those on the old Ontel Corp. keyboards as well. I used to repair those after Visual acquired the company.
If there's some generous French person in this comment section who happens to still have a Minitel he has no use for, please consider offering it to David. I'm sure he'd enjoy the hell outta this landmark of _télématique_ technology...
14:37 - Molex connectors are NOTORIOUS for flaky connections! IIRC, Southwest Technical Products' 6800 system (1975) in their infinite wisdom, used Molex connectors for data and address lines!
Great job on the cataract repair but you really should seal that thing ...
Those open corners,,, something's gonna get in there and it's gonna be visible and drive you nuts..
Put a little silicone from double stick to double stick and seal that thing.... :)
Wow. I used an ASM-3A from 1977 to 1978. Nice little terminal.
The aesthetic of the terminal is *chefs kiss*
Brave soul with your face that close to the caps first power up!
Spent the first couple of years as an EE using one of those to work on several computers including DEC 11/23s to program Fortan IV, assembly, and early CP/M computers to program assembly language on 8039 micros, and maybe other stuff - can't remember after 40 years 😂
siiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiCk! 110*f!!?? Don't bake to death out there, you're too precious to us.
Saw your gaff on 8 Bit Guy so I get why yr rabbit is that relaxed! Thank you for making the technical understandable!
Bonus Trivia - Bill Lear invented the 8 track stereo too.
I remember back in school in the early 90s, if I was stuck using an ADM-3A, you had to wiggle that pot, hold your breath, and hope for the right phase of the moon, to get a solid image.
"Fifty years of grime" - that would be a good title for a book
I've watched a bunch of cataract removal videos from Shango066 here on the 'Tube. Never saw him de-cataract a terminal though; Just antique televisions. Great work. Love this channel!
Bro you are amazing at bring back these historic items.
Also don't be disappointed by the picture wobble. Ours did that--a 1970's era building had too many magnetic fields to count!
My first experience with the ADM 3A was in 1985/1986 at SUNY at Buffalo. Along with VT220s and over VT100 compatible terminals was how we interfaced with the VAXes. It's also how we registered for classes.
I never really took to them because I couldn't use the full screen editor mode of EDT.
ADM-3A. I had one connected to the Altair 8800. Then moved it to a CPM-like OS called ISIS. I wish I could remember the manufacturer of that machine. Old memories triggered when that screen lit up!
My experience with CRTs is more with black & white TV CRTs. When I replaced one and discarded the old I would take it to the dump and knock the neck off with a ten foot pole. I never had any glass shards, the neck popped off cleanly. But I would recommend treating the CRT as if it were a bomb, eye protection at minimum. A face shield would be good.
I started watching your videos when you did a cameo with the 8bit guy and at first I thought your videos were too long but now I am hooked! Plz feel up the good work!
Great job! My only concern is that humid air could enter the space between the CRT and the protective glass and condense. It is amazing though, and it shaped up well!
Condensation isn't much of a problem as long as it can breathe. A bigger worry is dust, with static charge helping pull it in. Just needs some tape wrapped around the edges.
The chassis color and everything about it is a product of it's time when business machines were art... and it's glorious. Even cars like computer hardware kinda all looks the same now. Dealing with a 5 volt rail in something that ran the regulator hot enough to turn the screw to charcoal and what I think is a dead op-amp in some radio station gear while watching this. Keep up the awesome content. Just like in my industry while some of the hardware is getting rare but the people that know everything about it are even more so. Us young... ish.. guys have to learn this stuff and archive it the things that ain't in the manuals before it's gone. Glad you and other youtubers I already see in the comments are a part of that.
this is the highlight of my day
Vim fan remembering Bram, and the huge influence of the ADM-3A
Glad you got it going. These were awesome terminals when they came out. A huge step up from working on an ASR-33! I remember there was a big divider chain that generated all the frequencies from a single crystal; vertical and horizontal sync, dot clock, baud rates (getting 110 was complicated), all the way down to the cursor blink.
These were also famous for having primitive keyboards with no debounce circuitry. Sometimes pressing a key once would generate a bunch of that character. The "debounce" (such as it was) was provided purely by a capacitor somewhere in the key scan circuitry. And the fix was just to replace it with a larger capacitor. I don't remember the details, but it should be pretty simple to figure out if you've got the schematics. I think LSI even provided a retrofit kit.
Wow!! That turned out *really* well! Can't believe the missing IC was just lying in the bottom of the case, and that it worked perfectly fine! Very nice!
Great video. I've seen a few of your videos but this is the first one that caused me to subscribe. I'm old enough to have used many of the terminals mentioned. Including a Teletype ASR 33 with paper tape punch used in my first programming course in 1976 as a high school sophomore. I used to subscribe to the ACM Annals of the History of Computing journal because I think there is value is understanding the history of modern computers.
Very nice restoration. I'm amazed how good that Simple green worked on the power supply parts. You got super lucky with the finding of the missing chip. That text looks great on there and the keyboard works great after 47 years!
Lear was also behind the 8-track tape format! (Sorry if it’s mentioned already, I didn’t look through all the comments)
14 1-bit RAM chips makes sense - ASCII only needs 7 bits. So you have 2K of 7-bit character storage.
Wow, really fun project, thank you.
Great job Dave. Really enjoy your videos and that terminal is a real looker!
Never seen such machinery live. But interresting A.F.!
The keyboard in this terminal seems to be Hi-Tek switch grid / Stackpole. Key tops for those aren't that uncommon, so I am sure you can find replacements.
Great job on the cataracts repair!
Great job restoring this beautiful computer!!
You should put some tape around the edges of the front glass to prevent dust ingress, which the HV during operation has more than a slight ability to attract, and once it's under the glass in the air space you're not getting it out without pulling the front glass off again...
Awesome fix for the cataract issue!!
I've had issues with caps in a 1958 tube/valve radio and also on an MD recorder - supplying caps with power for a while or switching on and off will usually caps that are still sleeping because of not being used in ages.
These terminals made with all TTL chips and no micro were as close as you could get to a glass tty. Very little in the way of control codes. There might be a screen clear sequence but quitely likely not. It used to be that you'd just send a stack of line feeds to push the contents off the screen and then if need be send a home character, if it even had that ability, or simply send out a whole screen of output and watch it slowly work it's way up the screen. Implementing an actual screen clear in discrete logic is certainly possible, say trigger a counter + sending LFs and finally clear the cursor register triggered of the terminal count but it all takes real estate.
This terminal is very reminiscent of the terminal a friend had that I mentioned in another comment a while ago, except that one didn't even have a UART. Serial was done with individual chips in that one.
You have such great skills on these old machines. Love watching your videos.
You can get an even sharper image if you get rid of the air gap between the shield and screen. LOCA glue is usually made for stuff like this. The only downside is that it's permanent. But then again, that gap is so big that it might be impossible to put an even layer on there, it would drip to the sides.
Bro amazing as always...too much to learn from you. Salutes from Costa Rica.
That is a nice looking terminal. Sure does have plenty of 1960's influence in it's design. Good thing for those excessive heat warnings you have been getting down to help out with this project.