Sorry it took so long.. covid blew up 3 weeks in April. And brain fog is a real thing. But I did get it together and invested in a new Yeti X mic which I hope will put our audio problems to rest. Enjoy and thanks so much for watching!
I highly recommend not using noise reduction with this new mic. A little hiss is a lot more tolerable than the warbling artifacts that NR introduces. Love the channel!
@Nny Yeah, this thing is nasty! My girlfriend caught it mid 2020, lost her sense of smell completely, it's still really slowly coming back; after 1.5 year of relationship she sent me a message saying something like "holy shit, I can finally detect and recognise your smell!!?"
"I hear EEPROM island is a nice place to visit, but just don't get too much sun" ...Sir, you are an electronics nerd of the highest magnitude, I tip my hat to you!
40 years ago some guy was having the same problems with his homebrew and gave up, unaware that someday someone would pick up his work without knowing it never worked. ;)
I find this kind of thought mind-boggling, almost! It's like when you're working on an old car & you have to pull something buried for the first time in the vehicle's life - I wonder about the human that put it there - who were they, what kind of a life did they have, etc!
Same. It's why I love thrifting and finding old shit on ebay and etsy. Though most "other people's garbage" I tend to buy are vintage clothes, audio tapes, and records and maybe the odd computer thing or two. lol
The first EEPROM, whose contents are shown at 22:20, looks like it's being used to decode specific control characters. They're using the EEPROM to replace a pile of decoding logic, by feeding the character code into the address pins and then having the eight data pins out of the EEPROM each indicate a specific character match. Notice how all the codes are 0x00 except for 8 characters (0x07, 0x09, 0x0B, 0x0C, 0x10, 0x16, 0x1A, 0x1C) each of which will set exactly one output line from the EEPROM high. This would have been used to generate control lines that trigger events such as backspace and newline to happen when those keys were pressed. I'm not sure what specific characters they're decoding, this looks like it might not be using the standard ASCII mapping. The second EEPROM, contents shown at 22:22, looks like it's performing some kind of character remapping. In a similar way to the previous EEPROM, the character code from the keyboard would be fed into the address lines, and the data out would then contain the remapped character code. It looks like most of the characters are passed through unchanged, as the data contents of the EEPROM are equal to the address for most of the address inputs, but characters in the range 00-0F and 7E-7F have been remapped. I'm not completely sure why they needed this, maybe the character generator chip doesn't have the same character mapping as the keyboard and they needed to change some things around. The third EEPROM, contents shown at 22:32, looks like it's also being used to generate specific control signals based on the character inputs. Most of the values in this EEPROM are 0x80, and I suspect that was being used to generate the signal to move the cursor one space to the right after a normal character was typed. It's also generating some other codes for some of the remapped and control characters, though again I'm not sure what as I don't know what the mapping is. Perhaps this one is being used to generate cursor movement in general? I'd have to see the schematic to say for sure.
On further examination, the first EPROM seems to be decoding bell, horizontal tab, vertical tab, form feed, DLE, idle, and either start of text and end of text, or substitute and file character control codes. The second one is remapping many of the ASCII control characters while leaving the actual printable characters unchanged. I'm not sure why, maybe this thing originally used a non-ASCII keyboard and then when they changed it to use an ASCII one the builder decided it was easier to remap the control characters rather than rework the logic elsewhere. The third EPROM looks like it's decoding line feed, escape, and maybe backspace and carriage return. And the EPROM whose contents are shown at 22:47 is just baffling. That doesn't look like a lookup table. Might be some kind of state engine, I'd have to see what the surrounding circuitry looks like to know for sure.
@@ellindsey000 What an adventure to have computers in 1975.. Eproms (250ns) whre to slow back then for video state machine. you need a fast 82s100 or similar to do this. the screen wobeling could be a issue with grounding and of course powersupply caps. you get the 60hz inside the video generator (output amp?) I see at the end that the television is wipe on side if you have much screen content - please check video level on outout - seems the output amp is overdriven (!) - shouldn´t be more than 1V (!) on the output Vpp at 75 Ohms as I remember.
Most of that is stuff straight from a 1970s Radio Shack. They had those Archer breadboards with edge connectors as well as IC sockets with wire wrap posts. It's amazing that back then anyone could walk into a Radio Shack then go home and build something like this.
I would give anything to be able to do that sort of thing. I was too young when Radio Shacks really were Radio Shacks.. most of my life they've been basically retail toy/stereo/computer dealers.. and then later The Source (Canada).. which at most would sell you solder and some wire.
@@TechTimeTraveller They still had some hobby stuff as late as the 1990s. In 1991 I was working on a client's computer in the middle of nowhere Minnesota and saw that one board had been configured wrong when it we shipped it to the client. Two pins needed a shorting block which I didn't have because I'm a software person. I was tempted to use a paperclip or something, but I saw there was a Radio Shack across the street. I went in and that place *still* had a wire wrap tool and wire wrap! So I was able to do a professional job shorting the two pins.
It's annoying how hard it is to find electronic components in person nowadays, yeah online stores mean the amount of components anyone can get has gone up considerably, but the inability to actually check the physical thing before buying it, and having to wait multiple days and pay extra fees for shipping, has made the hobby harder in some ways.
@@asteroidrules Also it sucks when you just need a capacitor or resistor and the shipping is $5 then you have to wait for a week. Back then you could go to any Radio Shack in the country and get these components for a few cents. One day at school I decided to build a headphone amplifier, so after school I went to Radio Shack and got *all* of the components including a 741 op amp and had the thing completed that evening.
There's a TV series called Graveyard Cars where they restore classic cars found in horrible condition. Maybe you should call these episodes Graveyard Hardwares?
Guy here on TH-cam called shango066 does a series of videos called resurrections, not restorations as he's not changing every part, but changing just enough to bring it back to life. Could also call it a ressurection. If you like that type of content might wanna check him out too
Except just like it's one lego brick and two lego bricks (there's no such thing as 'legos' except something that belongs to lego), the plural of hardware is hardware
"Radio shack with a bad case of Norovirus" Sweet Lord, my sides 😂 Welcome back. I work for public transit in a high exposure role. Have had the Vid a few times now. The brain fog is a real thing. Glad you made it. Endorsing more intro skits with tortured internal dialogues. Edit: Eeprom Island UV exposure jokes are high art. 🏝️
This is such a cool mutant machine. Good on you for spending the effort to unearth its functions to try and put it back to work. It sure feels like you're close.
Back in the day I had that Radio Shack keyboard PCB. I was going to build a Cosmac Elf and try interfacing that keyboard to it. But the skills of teenager me weren't up to the challenge. It didn't help that in a few years I was able to buy an Atari 800 xl for less than the cost to finish it.
@@TechTimeTraveller The Popular Electronics articles described how to interface a parallel device to the Elf's data bus. So a machine instruction could read from the keyboard using an input instruction. For output I was thinking of using the 1861 pixie graphics chip. To glue this all together would require a ROM monitor reading, bitmap generation, and display. My ideas were sound, but I lacked the skills to pull them off.
Yeah I so rarely get to do that. It sucks that we are losing all these first generation home computer guys to age. The rare times I'm able to talk to the original owner I get troves of interesting insights.
@@TechTimeTraveller Most of the people still alive from that time period who were involved with computers are in their late 70s and are retired teachers/uni professors who worked with Minicomputers such as the PDP and IBM System/ series as opposed to first generation home micro. Unfortunately it's very rare to find anyone still alive who were early home micro hobbyists, especially ones with enough knowledge and money to build something like this home brew lower case as well as upper case ASCII terminal. Considering it was found in a shed, it's very likely the person who passed away was likely an inheritor of the device themselves.
The commentary here was hilarious, this computer is probably the kind of thing I would've made had I been alive at this point. And I love how a few of the EEPROMS are just fully uncovered - be a shame if a little UV light was to come along!
since corruption is pretty unlikely to occur indoors (UV has to be of specific wavelength and maintain for some time) hobbyists tended to be a little loosey-goosey. personally I'm fine with my arcade PCBs having some bare eproms, besides them only ever seeing LED light the data is non-unique and code has self-tests. some of them have been exposed afaik for 40 years w/o issues, but of course being more cautious doesn't cost anything either.
@@TechTimeTraveller Seems probable that it spent an afternoon in the sun when the shed was emptied. You did find a blank one, can't think of a use case for that.
In actual fact erasing an EPROM takes a LOT of very short wavelength UV to do anything. I used them professionally back in their heyday and erasing one took 5 minutes with the chip nearly touching a short wave UV lamp. I built my own eraser for home use by getting a germicidal lamp at a beauty supply place (they use them to kill germs on hair clippers) and putting it in a cheap under counter fluorescent fixture. If you don't get a strong smell of ozone from your lamp it will NOT erase an EPROM! I tried using direct sunlight to erase EPROMs and it just doesn't work. I put several in direct sunlight for a couple of days and they not only didn't erase, they still passed verification test when checked against original contents. I never covered any EPROMs windows when building equipment and never had any of them fail...
Another amazing video! It's always a wonderful day when you post a new one, I love old tech and it's great to actually learn some more about what came before modern computers.
In the 80's most all of the circuit boards I built at work and home were wire wrap boards. You'd be surprised at how fast you can put a prototype together.
The multiple line garbage characters my attribute to sync signal issues and bad latches. Try probing with scope. The 0:08 😂😁 is a real problem to acquire old tech and convince that it is worth it. Cheers!!
The worst is to convince the seller that the old tech is not worth what he thinks. Just yesterday I was talking with a seller that had some ISA cards (VGA, sound and some proprietary one made on a ISA protoboard) that they are not worth 600€ nor for collection nor for being vintage. I mean 200€ for a ISA card just because "vintage"? And to think that others scrap them just to get few cents worth of gold...
@@sebastian19745 Some ISA GPUs go for crazy prices these days. Damn U retro hype. Was glad I got a working et4000 ISA for around 50 that works in my ST. And yes, scrappers are pure cancer. Seen a guys yt channel and how hes "kinda into retro too" while breaking chips off old machines all day. Yeah no, you arent.
With regard to EPROM uses. Ben Eater has a video where he replaces a ton of discreet logic ICs with a single EEPROM, and made a comment that any collection of logic ICs can be replaced by one. After that programmable logic made a lot more sense to me.
Yeah I guess as a relative novice my issue is I'm used to EPROMs as a data storage device for things like system monitor, BASIC etc.. I haven't really wrapped my head around how the data burned into one is used is the absence of a processor. I should have known it could be... many machines I have use an EPROM for keyboard encoding. I'm gonna have to watch those videos now.
@@TechTimeTraveller imo it's probably all that talk about inputs being "addresses" that make people think of EPROMs only as data storage devices but yea physically they're just a big collection of programmable transistors (act of programming jams the gate into a desired position)
@@TechTimeTraveller Just think to a circuit that have only logic gates as a box with some inputs and some outputs. Take the inputs as the addresses lines of the EPROM and the outputs as the data lines. Now calculate for each combination possible of inputs the outputs result and write that data at the respective address. When replace the circuit with the EPROM, yo have the same functionality but less ICs so a simplest way to implement a schematic. Unfortunately, that approach was made many times and were used masked PROMS instead EPROMS to replace a CLC. When the PROM died, it is impossible to figure what circuit it replaced. I had an old computer that I want to rebuild but although I have the schematic, there is a bipolar PROM that nobody took the time to read, so that part of the circuit is impossible to build; also there are few computers in existence afaik.
I remember learning about Pal/gal logic in school. Write the equation and enter the code. Hit program. Your address decoder that took 17 74HCT chips is replaced with one.
Back in the 70s, microprocessors were expensive and ones able to execute meaningful programs almost non-existent. Hard-wired logic and logic design was both science and an art form. Far from just using bits and pieces lying around in the junk box, the designer would have gone to a lot of trouble to design this with all its video timing (sync pulses etc.) and it would have cost him/her a good deal. The machine was originally known as a dumb terminal (a display/input device) communicating with a computer via a UART-fed RS-232 interface. EPROMS were used for a number of functions in those days; specifically ASCII-encoding of a keyboard matrix, character-generation, a simple way of deriving timing signals from a binary counter rather than using a plethora of decoding logic and so-on. Erasable devices make bug-fixing, design modification and feature-adding easy. While the mains wiring is quite unsafe, I guess the builder never intended the unit to be used by others. It should never have been sold in that condition. I built such a terminal back in the early 1980's using a 6809 micro for doing all the smarts, a 6845 programmable video controller for generating the video timing signals, character memory addressing and so-on. Mine is in my study, is clean and tidy has all the smarts and video logic on a single PC board, the keyboard encoder on another and still works (uses the same keyboard as this one incidentally). The operating system for my terminal runs to 40 or so pages of commented 6809 code. I designed my own EPROM keyboard encoder and character generator and included a static RAM for programmable characters. Please do not be too disparaging of the efforts of early builders and hobbyists. I could say an awful lot in a similar tone about the disposable garbage that is built and sold these days with the sole object of making money. And these days I answer questions on another forum in the vein of, "how do I build a logic circuit to give a 0 output if A and B and ~C =1?", never mind the intelligence required to design something like "the Computer Thing From Hell". BTW the two main sources of problems you will run into with hardware built like this is poor IC pin to socket contacts caused by poor tinning on the IC pins, corrosion in the sockets, de-springing of the socket contacts themselves and above all, bead tantalum capacitors. I would replace all of the latter - they can short-circuit for no good reason at any time. They were often used for voltage regulator bypassing due to their low-ESR characteristics but modern miniature electrolytics with short leads will do the job just as well. And shorted power supplies in a system containing multiple-supply chips (like the old 2101s and other NMOS devices) can also cause chip failure. Taking time to scrape corrosion off the IC pins and applying good contact treatment to the sockets (or removing the sockets and soldering the chips in directly better still) can save a lot of trouble-shooting time in the long run. One last little thing: the wavy picture suggests that the picture tube yoke is being influenced by stray magnetic fields from a nearby mains-frequency power transformer.
Those green edge-connectors were the bane of HP repair technicians in the 1970s and 80s. The plastic expanded, causing the middle connectors to lose contact!
I've watched this video several times, still amazes me how you bring these old machines back to life. It is a real shame the seller separated the terminal and the computer, this guy obviously had his own way of doing things and having both would have been quite a treat :) I hope someday the guy who bought it sees your video and leaves some contact info so we can bring the two machines together again.
Unfortunately separation seems to be common. I try to assume it's just because these sellers buy things in a group and not because they're just trying to wring as much $ as possible from the deal. Some unfortunately do that with systems that have valuable keyboards unfortunately.
With all of the unique early video generating homebrew type machines you've displayed, I'm surprised you had not yet encountered BNC before in a practical setting. Great delving into a one-of-a-kind homemade machine.
I've seen them before.. not often.. but I don't think I've featured it in a video and I often forget what the proper name is. Most of my really old machines use a much bigger kinda RCA looking thing that has a collar that screws on.. I regret I don't remember the name of that one at all.
@@TechTimeTraveller Possibly the SO-239 also known as "UHF-Female" and PL-259 also known as "UHF-Male". 4donline.ihs.com/images/VipMasterIC/IC/AMPH/AMPH-S-A0001396201/AMPH-S-A0001292064-1.pdf?hkey=52A5661711E402568146F3353EA87419 I think these used to be fairly common on monochrome CCTV monitors, which were often used with early micro computers.
Welcome back. You and your videos are worth waiting for. Glad you are feeling better and the brain fog is abating. I really enjoy your videos and lmfao regularly at them. Your deadpan is fantastic.
It was unsatisfying not to get a successful conclusion to this. Still, I'm impressed by your technichal savvy, your sleuthing skills, your near-angelic patience, and, frankly, your courage. I hope you crack this nut.
What a monster! It makes the "generative ambient modular" Euro-rack spaghetti set-ups that populate my home page look downright manageable by comparison.
I took a TV and film production course many years ago, and I kept calling BNC cables BNP cables by mistake. omg those wobbly characters are sick, I could look at those all day.
@@TechTimeTraveller How often did systems use hardware for audio encoding/decoding, and how often was that left to software? The only time I would think hardware would offer a big advantage would be if it would allow a system to boot off tape without needing a custom ROM, but from what I can tell hardware decoding was pretty common.
I've seen a lot of old computers, and all that I can say thanks for a look at some very old and interesting computer hardware. The guy who put this machine together was a genius of his time!!
I immediately thought “Don Lancaster-TV typewriter”. My misspent youth following Steve Circia’s Circuit Cellar in Byte mag happily wire wrapping a Zilog sbc then a 8051 sbc.
This thing reminds me of some weird kitchen gadget nobody knows the name of anymore. Clearly it had some purpose, it was made for a reason, but nobody knows what it is, and the more you try to guess, the more you are confused.
My (non-expert) opinion is that this thing was either modified to over a long period of time to add more features, etc., or, possibly, it was a collaborative effort among several people. This would explain the multiple different circuit boards and overall bodged-together style.
Could be. The estate saler seemed pretty convinced he was a lone inventor kinda guy.. so probably over time. Maybe the whole thing was set up differently in the beginning.
Do the date codes on the chips support this theory? Are some parts obviously older than others? (I do realise that a hard-core hobbyist would have an inventory of parts on hand, but we can only analyze the existing evidence.)
Most of the chips look to me to be Radio Shack parts from the era. (The rest would be mail-order.) A lot of the chips Radio Shack sold were probably surplus, so in the late '70s you would find a bunch with 71-74 dates, sometimes earlier, and quite a variety of package and labeling styles. And there's a good chance that the basic design came from some magazine from the late '70s.
Why it often looks like that people living in 110V countries are more hysterical about main voltage than those living in 220v countries? Yes, a fuse is something useful. yes the mains connection of that device is somewhat horrendous and covering it with electrical tape is recommend. but it's hardly necessary to make such a fuss about it. What would be really helpful and a much greater safety feature is having a GFCI breaker (residual-current circuit breaker / ground fault circuit interrupter) either in your home's circuit breaker box or seperate at your test bench.
I love your editing style so much, it's so simplistic but it gets me every time. Also, head n shoulders didn't help me as shampoo, it just made my hair greasier XD
I love old home built interesting computer-thingies. Unfortunately I don't have that much time for such things but at least I enjoyed watching you mess with yours!
Aiii was so hyped for this video! Amazing love how you do your videos with funny intermissions but at the same just beeing so interesting and full of facts !
I literally just finished reading a chapter in a book bitching about the unreliability of those early intel ram chips, especially the 1103 apparently it was an enormous issue but the tech was so new that people tolerated them, xerox PARC built a pdp10 clone using the 1103s but tons of the chips were just junk on arrival.
Yeah I'm kind of dreading building my Mark 8.. I bought a ton of 1101s for that project.. they were *not* cheap, and I bet a lot of them are probably quite dead.
@@TechTimeTraveller that would be about right, hopefully you got a good batch, from what I read a minuscule amount of what they produced passed QA, and then most of those failed not too long after too. If a company did that these days they’d have been given the boot well and truly. It’s amazing how early innovation was that crucial that designers were willing to tolerate things like the Altair being produced at a snails pace or intel producing mostly duds.
Thanks so much for making this video, any chance of some high resolution images of the front and backs of the various boards, it would be good to have a proper look and see what each board does. I hope you're recovering from Covid well, me and my family have avoided it so far here, but I'm sure I will get it in time.
I use BNC connectors on a regular basis at work, to the point I have ~20 BNC barrels for extending cables floating around my car. They are a standard for ENG and live video production and can push up to 24GB/sec
The connector was named the BNC (for Bayonet Neill-Concelman) after its bayonet mount locking mechanism and its inventors, Paul Neill and Carl Concelman. Neill worked at Bell Labs and also invented the N connector; Concelman worked at Amphenol and also invented the C connector. (Source Wikipedia)
Thank you! Was BNC applied just to those smaller locking types? On some of my monitors I have a port that resembles a super sized RCA phono style plug with threads around the rim.. the connector that mates to it has a really big pin and screws onto it. I've read people referring to it as BNC but I don't think so. It's much larger.
The manufacturer of that keyboard for Tandy was the same one used to make the Dragon Data machines. It's not the same layout, but the board design in almost every way is identical including the font style. It's quite logical given Dragon Data machines were designed in tandem with the Tandy computers.
Oh, memories. I built a video terminal using the same Radio Shack ASCII keyboard encoder back in 1979 so I could get online nights/weekends when the timeshare system had no other users. Amazing dialup MODEM ran at 300 baud, much faster than the Teletype we had at school that was 110. The rest of my setup were kits from Electronic Systems : a TV typewriter that was 16 lines x 64 characters, Power supply, UART board, RF modulator so you could run the video into a TV set, and a MODEM.
I have been looking for one of those Electronics Systems TVT boards forever. They just don't come up for sale. Probably because they look like random electronic junk.
@@TechTimeTraveller Sad to admit that I threw the entire board set into the garbage about 30 years ago when I got a VT100 and a VT220 from a past employer, because those were considered to be junk. The only value of the TVT board set is nostalgic, and most TVs could not display 64 characters very well because of their limited video bandwidth. I got nice results with a color TV by turning off the blue and red guns; the remaining green had no convergence issues. Blue-only and red-only worked OK, though not as visible as green. I had a smaller black-and-white TV, and it was actually harder to read than color (green). I did keep the Electronic Systems power supply for a few more years. A year later I moved-up to a real 24x80 display (SD System VDB-8024), and that absolutely required a real video monitor, so the TVT got boxed-up and ignored. The MODEM worked surprisingly well; very few bit errors even at 300 baud on standard telco, and of course that was with acoustic coupling (speaker and mic). Direct-connect was not legal. I miss those days of real homebrewing. Hard to believe when you had 64Kbytes of memory, and a pair of 8-inch Shugart floppy drives you had a top-tier machine.
I wondered if the EPROM that had "nothing on it" was being used to clear the screen with some simple copy operations? Perhaps part of a bootstrapping circuit that isn't working?
The garbage on the screen looks like some kind of alien alphabet. I think it would make a great movie prop for some kind of alien/post apocalyptic sci-fi movie :)
@@michaelwright2986 or maybe it's the very thing John Titor (if you don't know who he is, look it up, but beware of the rabbit hole :)) was looking for :)
@@Bata.andrei Somehow, I missed him the first time round. And now the Time Cube only exists on the Wayback Machine, which is kind of too meta for words. I must read again Thief of Time, by Terry Pratchett.
Yeah thats why I kinda rag on estate salers a little bit sometimes. They often don't take the time to research what they have (they can't.. they need to get stuff sold asap).. or they break up pieces to maximize $. The ones that break up mechanical keyboards and their machines because the keyboard is worth more by itself really irk me.
That wavy display is quite a funky sight, I'm guessing the video generator is having some trouble with timing on the horizontal blanking, but it's significantly worse in the first third to half of each field where it's jumping at a regular interval. I'll be interested to see if re-capping the power supply fixes that, or there could be something wrong with the crystal oscillator.
I'd be leaning towards an analog problem with whatever is used as a video DAC, making the sync voltage levels not quite right. Not knowing the circuitry it could be drifted resistors or a bad discrete transistor, possibly a chip.
Yep, the horizontal sync voltage level is probably not quite (low?) enough for the cheap TV, and the cheap TV is being cheap and its scan is drifting a bit. Find out where the hsync signal comes from, fix it, and it should become stable. Oh, and there is no DAC because it's all digital, just a few different voltage levels switched by transistors and mixed together.
All those chips with 7430 stamped on them... I'm sure I had some like that came which from bulk packs at Radio Shack when I was a kid. But I checked my old chips and didn't find any. I did find a pair of 7440 chips with no other marking than the big white numbers, though. With the other parts, it's clear that he got most of his parts from Radio Shack. I even used three of those same boards/connectors to try to make an 8080A computer back in 1979. (It would never have worked because I didn't understand TTL fan-out, or even testing a subsystem at a time.)
This reminds me of fixing a Sharp Twin Fami 20 years ago! I got it super cheap "broken" and after months of tinkering off and on, I realised to my horror someone had replaced the belt, but had NOT marked the stack of analog gears when they took it apart and put them together randomly!! After a lot of playing with it I finally got things aligned. Then I put it away and tried to play it months later. I tried to play and nothing would work. The belt had rotted 🤣🤣😂 Eventually i got it working 🤣
I know not a whole lot about computers, but have you thought that maybe the computer it was built to hook up to (that got sold separately) was also modified and so they only were meant to work together?
Wire wrap was awesome. BRING BACK WIREWRAP. 8:47 that's because it IS cardboard. Phenolic resin impregnated paper fiber, to be precise (modern pcbs use FR4)
It's not unusual for a cheap '70s terminal not to have a clear screen code. The CT-1024 did not, which is why the SWTPC monitor's "C" command sends a "home-up" ($10) followed by "erase to end of frame" ($16).
Maybe this homebrew terminal and the 8800 were put in the shed because the builder couldn't get them working right? I suspect this was an unfinished hobby project, based on the unsafe wiring and lack of a cover for it.
I'm watching this on a computer that I built thinking to myself "some dude in the future is going to buy my computer at an estate sale and pick it apart like this, wondering what I did"
That looks like a proper Cherry key keyboard, they were about £40 each in the late 1970s. Call it £400 now... The +5V regulator is over there because you want it near to your board. Of course, they must have had to compromise!
See the little metal fingers? That's a Stackpole or HiTek type of key mechanism. Radio Shack used them in early TRS-80s, and they're also found in the ADM-3A terminal. They were quite nice to type on, as long as you had good debounce.
I hope the original builder of this or someone who knew them eventually sees this video and lets you know what its for. Maybe the modified system it connected to did something else. Could it be a cypher machine of some sort? Maybe im dreaming.
Sorry it took so long.. covid blew up 3 weeks in April. And brain fog is a real thing. But I did get it together and invested in a new Yeti X mic which I hope will put our audio problems to rest. Enjoy and thanks so much for watching!
I highly recommend not using noise reduction with this new mic. A little hiss is a lot more tolerable than the warbling artifacts that NR introduces. Love the channel!
I'm glad you made it out the other end ok.
Sounds great
@Nny Yeah, this thing is nasty!
My girlfriend caught it mid 2020, lost her sense of smell completely, it's still really slowly coming back; after 1.5 year of relationship she sent me a message saying something like "holy shit, I can finally detect and recognise your smell!!?"
No worries, take care!
"I hear EEPROM island is a nice place to visit, but just don't get too much sun" ...Sir, you are an electronics nerd of the highest magnitude, I tip my hat to you!
4:03 I concur!
Yeah, that took me a minute but I get it...
It wasn't until he completely faded away that I realised what the joke was, but it was still funny
I had myself laughing at that one. My wife was looking at me funny
*EPROM.
EEPROM isn't light sensitive.
40 years ago some guy was having the same problems with his homebrew and gave up, unaware that someday someone would pick up his work without knowing it never worked. ;)
This is exactly what i was thinking :)
I find this kind of thought mind-boggling, almost!
It's like when you're working on an old car & you have to pull something buried for the first time in the vehicle's life - I wonder about the human that put it there - who were they, what kind of a life did they have, etc!
That introduction was absolutely amazing... and so very true.... I have a terrible problem with "other people's garbage"
Same. It's why I love thrifting and finding old shit on ebay and etsy. Though most "other people's garbage" I tend to buy are vintage clothes, audio tapes, and records and maybe the odd computer thing or two. lol
The first EEPROM, whose contents are shown at 22:20, looks like it's being used to decode specific control characters. They're using the EEPROM to replace a pile of decoding logic, by feeding the character code into the address pins and then having the eight data pins out of the EEPROM each indicate a specific character match. Notice how all the codes are 0x00 except for 8 characters (0x07, 0x09, 0x0B, 0x0C, 0x10, 0x16, 0x1A, 0x1C) each of which will set exactly one output line from the EEPROM high. This would have been used to generate control lines that trigger events such as backspace and newline to happen when those keys were pressed. I'm not sure what specific characters they're decoding, this looks like it might not be using the standard ASCII mapping.
The second EEPROM, contents shown at 22:22, looks like it's performing some kind of character remapping. In a similar way to the previous EEPROM, the character code from the keyboard would be fed into the address lines, and the data out would then contain the remapped character code. It looks like most of the characters are passed through unchanged, as the data contents of the EEPROM are equal to the address for most of the address inputs, but characters in the range 00-0F and 7E-7F have been remapped. I'm not completely sure why they needed this, maybe the character generator chip doesn't have the same character mapping as the keyboard and they needed to change some things around.
The third EEPROM, contents shown at 22:32, looks like it's also being used to generate specific control signals based on the character inputs. Most of the values in this EEPROM are 0x80, and I suspect that was being used to generate the signal to move the cursor one space to the right after a normal character was typed. It's also generating some other codes for some of the remapped and control characters, though again I'm not sure what as I don't know what the mapping is. Perhaps this one is being used to generate cursor movement in general? I'd have to see the schematic to say for sure.
On further examination, the first EPROM seems to be decoding bell, horizontal tab, vertical tab, form feed, DLE, idle, and either start of text and end of text, or substitute and file character control codes. The second one is remapping many of the ASCII control characters while leaving the actual printable characters unchanged. I'm not sure why, maybe this thing originally used a non-ASCII keyboard and then when they changed it to use an ASCII one the builder decided it was easier to remap the control characters rather than rework the logic elsewhere. The third EPROM looks like it's decoding line feed, escape, and maybe backspace and carriage return. And the EPROM whose contents are shown at 22:47 is just baffling. That doesn't look like a lookup table. Might be some kind of state engine, I'd have to see what the surrounding circuitry looks like to know for sure.
@@ellindsey000 What an adventure to have computers in 1975.. Eproms (250ns) whre to slow back then for video state machine. you need a fast 82s100 or similar to do this. the screen wobeling could be a issue with grounding and of course powersupply caps. you get the 60hz inside the video generator (output amp?)
I see at the end that the television is wipe on side if you have much screen content - please check video level on outout - seems the output amp is overdriven (!) - shouldn´t be more than 1V (!) on the output Vpp at 75 Ohms as I remember.
Most of that is stuff straight from a 1970s Radio Shack. They had those Archer breadboards with edge connectors as well as IC sockets with wire wrap posts. It's amazing that back then anyone could walk into a Radio Shack then go home and build something like this.
I would give anything to be able to do that sort of thing. I was too young when Radio Shacks really were Radio Shacks.. most of my life they've been basically retail toy/stereo/computer dealers.. and then later The Source (Canada).. which at most would sell you solder and some wire.
@@TechTimeTraveller They still had some hobby stuff as late as the 1990s. In 1991 I was working on a client's computer in the middle of nowhere Minnesota and saw that one board had been configured wrong when it we shipped it to the client. Two pins needed a shorting block which I didn't have because I'm a software person. I was tempted to use a paperclip or something, but I saw there was a Radio Shack across the street. I went in and that place *still* had a wire wrap tool and wire wrap! So I was able to do a professional job shorting the two pins.
It's annoying how hard it is to find electronic components in person nowadays, yeah online stores mean the amount of components anyone can get has gone up considerably, but the inability to actually check the physical thing before buying it, and having to wait multiple days and pay extra fees for shipping, has made the hobby harder in some ways.
@@asteroidrules I really struggle with buying parts like the card slot etc.. as you said it's really nice to be able to see the physical thing.
@@asteroidrules Also it sucks when you just need a capacitor or resistor and the shipping is $5 then you have to wait for a week. Back then you could go to any Radio Shack in the country and get these components for a few cents. One day at school I decided to build a headphone amplifier, so after school I went to Radio Shack and got *all* of the components including a 741 op amp and had the thing completed that evening.
There's a TV series called Graveyard Cars where they restore classic cars found in horrible condition. Maybe you should call these episodes Graveyard Hardwares?
Guy here on TH-cam called shango066 does a series of videos called resurrections, not restorations as he's not changing every part, but changing just enough to bring it back to life. Could also call it a ressurection.
If you like that type of content might wanna check him out too
My dad calls my old PC collection "the computer graveyard"
“Graveyard Hardware” would actually makes sense in our dialect of English :*
@@askhowiknow5527 graveyhardware
Except just like it's one lego brick and two lego bricks (there's no such thing as 'legos' except something that belongs to lego), the plural of hardware is hardware
"Radio shack with a bad case of Norovirus"
Sweet Lord, my sides 😂
Welcome back.
I work for public transit in a high exposure role. Have had the Vid a few times now. The brain fog is a real thing. Glad you made it.
Endorsing more intro skits with tortured internal dialogues.
Edit: Eeprom Island UV exposure jokes are high art. 🏝️
Funny, I was just in a Radio Shack last week
I lost it at "here a prom, there a prom, why does it need any rom" 😂
That thing is definitely computer
It’s the computerist thing I’ve ever seen
This is such a cool mutant machine. Good on you for spending the effort to unearth its functions to try and put it back to work. It sure feels like you're close.
Back in the day I had that Radio Shack keyboard PCB. I was going to build a Cosmac Elf and try interfacing that keyboard to it. But the skills of teenager me weren't up to the challenge. It didn't help that in a few years I was able to buy an Atari 800 xl for less than the cost to finish it.
I never understood how you'd use an ELF with a keyboard. Were you planning to have it do video output also?
@@TechTimeTraveller The Popular Electronics articles described how to interface a parallel device to the Elf's data bus. So a machine instruction could read from the keyboard using an input instruction. For output I was thinking of using the 1861 pixie graphics chip. To glue this all together would require a ROM monitor reading, bitmap generation, and display. My ideas were sound, but I lacked the skills to pull them off.
It really is a shame that it was an estate sale you got it from. It would be so interesting to pick the brain of who ever made this.
Yeah I so rarely get to do that. It sucks that we are losing all these first generation home computer guys to age. The rare times I'm able to talk to the original owner I get troves of interesting insights.
@@TechTimeTraveller Most of the people still alive from that time period who were involved with computers are in their late 70s and are retired teachers/uni professors who worked with Minicomputers such as the PDP and IBM System/ series as opposed to first generation home micro. Unfortunately it's very rare to find anyone still alive who were early home micro hobbyists, especially ones with enough knowledge and money to build something like this home brew lower case as well as upper case ASCII terminal.
Considering it was found in a shed, it's very likely the person who passed away was likely an inheritor of the device themselves.
The commentary here was hilarious, this computer is probably the kind of thing I would've made had I been alive at this point. And I love how a few of the EEPROMS are just fully uncovered - be a shame if a little UV light was to come along!
Yup.. actually all but one EPROM was uncovered when I got it. I see that a lot on 1702a era equipment. I guess they normally resided under a cover.
since corruption is pretty unlikely to occur indoors (UV has to be of specific wavelength and maintain for some time) hobbyists tended to be a little loosey-goosey. personally I'm fine with my arcade PCBs having some bare eproms, besides them only ever seeing LED light the data is non-unique and code has self-tests. some of them have been exposed afaik for 40 years w/o issues, but of course being more cautious doesn't cost anything either.
@@TechTimeTraveller Seems probable that it spent an afternoon in the sun when the shed was emptied. You did find a blank one, can't think of a use case for that.
In actual fact erasing an EPROM takes a LOT of very short wavelength UV to do anything. I used them professionally back in their heyday and erasing one took 5 minutes with the chip nearly touching a short wave UV lamp. I built my own eraser for home use by getting a germicidal lamp at a beauty supply place (they use them to kill germs on hair clippers) and putting it in a cheap under counter fluorescent fixture. If you don't get a strong smell of ozone from your lamp it will NOT erase an EPROM! I tried using direct sunlight to erase EPROMs and it just doesn't work. I put several in direct sunlight for a couple of days and they not only didn't erase, they still passed verification test when checked against original contents. I never covered any EPROMs windows when building equipment and never had any of them fail...
@@wb5mct Thank you, good to know! I had the misconception they were much more sensitive.
That floaty wavey effect around 13 minutes in is so cool. can see an analog horror series using it
Another amazing video! It's always a wonderful day when you post a new one, I love old tech and it's great to actually learn some more about what came before modern computers.
In the 80's most all of the circuit boards I built at work and home were wire wrap boards. You'd be surprised at how fast you can put a prototype together.
Bring back wirewrap!!!
The multiple line garbage characters my attribute to sync signal issues and bad latches. Try probing with scope.
The 0:08 😂😁 is a real problem to acquire old tech and convince that it is worth it.
Cheers!!
The worst is to convince the seller that the old tech is not worth what he thinks. Just yesterday I was talking with a seller that had some ISA cards (VGA, sound and some proprietary one made on a ISA protoboard) that they are not worth 600€ nor for collection nor for being vintage. I mean 200€ for a ISA card just because "vintage"? And to think that others scrap them just to get few cents worth of gold...
@@sebastian19745 Some ISA GPUs go for crazy prices these days. Damn U retro hype. Was glad I got a working et4000 ISA for around 50 that works in my ST. And yes, scrappers are pure cancer. Seen a guys yt channel and how hes "kinda into retro too" while breaking chips off old machines all day. Yeah no, you arent.
With regard to EPROM uses. Ben Eater has a video where he replaces a ton of discreet logic ICs with a single EEPROM, and made a comment that any collection of logic ICs can be replaced by one. After that programmable logic made a lot more sense to me.
Yeah I guess as a relative novice my issue is I'm used to EPROMs as a data storage device for things like system monitor, BASIC etc.. I haven't really wrapped my head around how the data burned into one is used is the absence of a processor. I should have known it could be... many machines I have use an EPROM for keyboard encoding. I'm gonna have to watch those videos now.
@@TechTimeTraveller imo it's probably all that talk about inputs being "addresses" that make people think of EPROMs only as data storage devices but yea physically they're just a big collection of programmable transistors (act of programming jams the gate into a desired position)
@@TechTimeTraveller Just think to a circuit that have only logic gates as a box with some inputs and some outputs. Take the inputs as the addresses lines of the EPROM and the outputs as the data lines. Now calculate for each combination possible of inputs the outputs result and write that data at the respective address. When replace the circuit with the EPROM, yo have the same functionality but less ICs so a simplest way to implement a schematic.
Unfortunately, that approach was made many times and were used masked PROMS instead EPROMS to replace a CLC. When the PROM died, it is impossible to figure what circuit it replaced. I had an old computer that I want to rebuild but although I have the schematic, there is a bipolar PROM that nobody took the time to read, so that part of the circuit is impossible to build; also there are few computers in existence afaik.
Similar to the PLA in a C64.
I remember learning about Pal/gal logic in school. Write the equation and enter the code. Hit program. Your address decoder that took 17 74HCT chips is replaced with one.
That radio shack joke aged me several years when I realized they’ve been closed since before I graduated high school
Back in the 70s, microprocessors were expensive and ones able to execute meaningful programs almost non-existent. Hard-wired logic and logic design was both science and an art form. Far from just using bits and pieces lying around in the junk box, the designer would have gone to a lot of trouble to design this with all its video timing (sync pulses etc.) and it would have cost him/her a good deal. The machine was originally known as a dumb terminal (a display/input device) communicating with a computer via a UART-fed RS-232 interface. EPROMS were used for a number of functions in those days; specifically ASCII-encoding of a keyboard matrix, character-generation, a simple way of deriving timing signals from a binary counter rather than using a plethora of decoding logic and so-on. Erasable devices make bug-fixing, design modification and feature-adding easy.
While the mains wiring is quite unsafe, I guess the builder never intended the unit to be used by others. It should never have been sold in that condition.
I built such a terminal back in the early 1980's using a 6809 micro for doing all the smarts, a 6845 programmable video controller for generating the video timing signals, character memory addressing and so-on. Mine is in my study, is clean and tidy has all the smarts and video logic on a single PC board, the keyboard encoder on another and still works (uses the same keyboard as this one incidentally). The operating system for my terminal runs to 40 or so pages of commented 6809 code. I designed my own EPROM keyboard encoder and character generator and included a static RAM for programmable characters.
Please do not be too disparaging of the efforts of early builders and hobbyists. I could say an awful lot in a similar tone about the disposable garbage that is built and sold these days with the sole object of making money. And these days I answer questions on another forum in the vein of, "how do I build a logic circuit to give a 0 output if A and B and ~C =1?", never mind the intelligence required to design something like "the Computer Thing From Hell".
BTW the two main sources of problems you will run into with hardware built like this is poor IC pin to socket contacts caused by poor tinning on the IC pins, corrosion in the sockets, de-springing of the socket contacts themselves and above all, bead tantalum capacitors. I would replace all of the latter - they can short-circuit for no good reason at any time. They were often used for voltage regulator bypassing due to their low-ESR characteristics but modern miniature electrolytics with short leads will do the job just as well. And shorted power supplies in a system containing multiple-supply chips (like the old 2101s and other NMOS devices) can also cause chip failure. Taking time to scrape corrosion off the IC pins and applying good contact treatment to the sockets (or removing the sockets and soldering the chips in directly better still) can save a lot of trouble-shooting time in the long run.
One last little thing: the wavy picture suggests that the picture tube yoke is being influenced by stray magnetic fields from a nearby mains-frequency power transformer.
Great video as usual - I love all the comedic touches you add to your videos, they really make them stand out!
BNC for video is not "old style", it is currently used in all pro video equipment.
Those green edge-connectors were the bane of HP repair technicians in the 1970s and 80s.
The plastic expanded, causing the middle connectors to lose contact!
I've watched this video several times, still amazes me how you bring these old machines back to life. It is a real shame the seller separated the terminal and the computer, this guy obviously had his own way of doing things and having both would have been quite a treat :) I hope someday the guy who bought it sees your video and leaves some contact info so we can bring the two machines together again.
Unfortunately separation seems to be common. I try to assume it's just because these sellers buy things in a group and not because they're just trying to wring as much $ as possible from the deal. Some unfortunately do that with systems that have valuable keyboards unfortunately.
With all of the unique early video generating homebrew type machines you've displayed, I'm surprised you had not yet encountered BNC before in a practical setting.
Great delving into a one-of-a-kind homemade machine.
I've seen them before.. not often.. but I don't think I've featured it in a video and I often forget what the proper name is. Most of my really old machines use a much bigger kinda RCA looking thing that has a collar that screws on.. I regret I don't remember the name of that one at all.
@@TechTimeTraveller Possibly the SO-239 also known as "UHF-Female" and PL-259 also known as "UHF-Male".
4donline.ihs.com/images/VipMasterIC/IC/AMPH/AMPH-S-A0001396201/AMPH-S-A0001292064-1.pdf?hkey=52A5661711E402568146F3353EA87419
I think these used to be fairly common on monochrome CCTV monitors, which were often used with early micro computers.
Welcome back. You and your videos are worth waiting for. Glad you are feeling better and the brain fog is abating. I really enjoy your videos and lmfao regularly at them. Your deadpan is fantastic.
Many thanks and much appreciated!!
This looks like it would control some scrap metal time machine in a apocalypse movie
It was unsatisfying not to get a successful conclusion to this. Still, I'm impressed by your technichal savvy, your sleuthing skills, your near-angelic patience, and, frankly, your courage. I hope you crack this nut.
That thing was probably the reason for the estate sale.
What a monster! It makes the "generative ambient modular" Euro-rack spaghetti set-ups that populate my home page look downright manageable by comparison.
I took a TV and film production course many years ago, and I kept calling BNC cables BNP cables by mistake.
omg those wobbly characters are sick, I could look at those all day.
Kind of hypnotic isn't it? 😀
This reminds me so much of my own hobby computer life around 1975-1980 !
I think, with the way the TV was acting, I'd drop a new crystal on there. That thing looked a bit sketch.
I am guessing that the "audio card" is the tape interface card.
Yup.. its basically the equivalent of SWTPC's AC30 tape encoder. Doesn't work unfortunately but probably could with some tuning.
@@TechTimeTraveller How often did systems use hardware for audio encoding/decoding, and how often was that left to software? The only time I would think hardware would offer a big advantage would be if it would allow a system to boot off tape without needing a custom ROM, but from what I can tell hardware decoding was pretty common.
I've seen a lot of old computers, and all that I can say thanks for a look at some very old and interesting computer hardware. The guy who put this machine together was a genius of his time!!
These are the obscure @BenHeckHacks reverse engineering videos I love. Excited to see what the future holds for this project.
That introduction is so good, I had to stop the video when it was over to come down here to tell you that.
Many thanks! I like to experiment a bit with different styles of intro.
If that guy were still around, he would think this video is awesome.
I am very happy you showed up in my recommendations. Wonderful video and presentation!
I immediately thought “Don Lancaster-TV typewriter”. My misspent youth following Steve Circia’s Circuit Cellar in Byte mag happily wire wrapping a Zilog sbc then a 8051 sbc.
This thing reminds me of some weird kitchen gadget nobody knows the name of anymore. Clearly it had some purpose, it was made for a reason, but nobody knows what it is, and the more you try to guess, the more you are confused.
This is super cool, I look forward to your progress and updates!
Great work something like this must be a bit of a nightmare to diagnose .
"No schematic? No problem!" 😀
My (non-expert) opinion is that this thing was either modified to over a long period of time to add more features, etc., or, possibly, it was a collaborative effort among several people. This would explain the multiple different circuit boards and overall bodged-together style.
Could be. The estate saler seemed pretty convinced he was a lone inventor kinda guy.. so probably over time. Maybe the whole thing was set up differently in the beginning.
Do the date codes on the chips support this theory? Are some parts obviously older than others? (I do realise that a hard-core hobbyist would have an inventory of parts on hand, but we can only analyze the existing evidence.)
Most of the chips look to me to be Radio Shack parts from the era. (The rest would be mail-order.) A lot of the chips Radio Shack sold were probably surplus, so in the late '70s you would find a bunch with 71-74 dates, sometimes earlier, and quite a variety of package and labeling styles.
And there's a good chance that the basic design came from some magazine from the late '70s.
Why it often looks like that people living in 110V countries are more hysterical about main voltage than those living in 220v countries?
Yes, a fuse is something useful.
yes the mains connection of that device is somewhat horrendous and covering it with electrical tape is recommend. but it's hardly necessary to make such a fuss about it.
What would be really helpful and a much greater safety feature is having a GFCI breaker (residual-current circuit breaker / ground fault circuit interrupter) either in your home's circuit breaker box or seperate at your test bench.
It's a shame you didn't get the computer this was made for. It's really cool though and really cool that you made so much progress.
I love your editing style so much, it's so simplistic but it gets me every time.
Also, head n shoulders didn't help me as shampoo, it just made my hair greasier XD
I envision a repair for that broken corner similar to how they fill in missing parts of fossil skulls.
Yer videos are so great - we need to get yer subs way up!! I’m in; I can see how much time goes in, I’d love yer help!! Great job, thanks for sharing.
Many thanks!
I love old home built interesting computer-thingies. Unfortunately I don't have that much time for such things but at least I enjoyed watching you mess with yours!
Aiii was so hyped for this video! Amazing love how you do your videos with funny intermissions but at the same just beeing so interesting and full of facts !
What an interesting machine! Thank you for showing it to us, even if you couldn't get it 100% working again. 🙂
I see a number of PolyPaks renumbered ICs. The big silver characters are the giveaway. Those were good days.
Your level of stick-tuitive-ness is off the charts.
Looks like you time traveled back to 1977 and then went dumpster diving In steve Wozniak's garbage.
Solder under strain or pressure will flow over time and break the connection.
essentially the benifits of homebrew from tyhe 70's. Even stored in the garbage pile it probably still ran up until you got it
I literally just finished reading a chapter in a book bitching about the unreliability of those early intel ram chips, especially the 1103 apparently it was an enormous issue but the tech was so new that people tolerated them, xerox PARC built a pdp10 clone using the 1103s but tons of the chips were just junk on arrival.
Yeah I'm kind of dreading building my Mark 8.. I bought a ton of 1101s for that project.. they were *not* cheap, and I bet a lot of them are probably quite dead.
@@TechTimeTraveller that would be about right, hopefully you got a good batch, from what I read a minuscule amount of what they produced passed QA, and then most of those failed not too long after too. If a company did that these days they’d have been given the boot well and truly. It’s amazing how early innovation was that crucial that designers were willing to tolerate things like the Altair being produced at a snails pace or intel producing mostly duds.
this is really cool
didnt really know about homebrew computers and terminals
Thanks so much for making this video, any chance of some high resolution images of the front and backs of the various boards, it would be good to have a proper look and see what each board does.
I hope you're recovering from Covid well, me and my family have avoided it so far here, but I'm sure I will get it in time.
I am working on a website to post stuff like this.. but I can put some high resolution photos up tomorrow in my Google drive.
@@TechTimeTraveller it would be interesting to have a look and see if the purpose of some the mystery boards could be worked out.
It’s the This Old Tony of tech! Keep up the good work!
The Borduper Conector Bort on The Right To me sins like an Internal Comunication Bord
I use BNC connectors on a regular basis at work, to the point I have ~20 BNC barrels for extending cables floating around my car. They are a standard for ENG and live video production and can push up to 24GB/sec
That thing looks cool. Glad you're feeling better.
The connector was named the BNC (for Bayonet Neill-Concelman) after its bayonet mount locking mechanism and its inventors, Paul Neill and Carl Concelman. Neill worked at Bell Labs and also invented the N connector; Concelman worked at Amphenol and also invented the C connector. (Source Wikipedia)
Thank you! Was BNC applied just to those smaller locking types? On some of my monitors I have a port that resembles a super sized RCA phono style plug with threads around the rim.. the connector that mates to it has a really big pin and screws onto it. I've read people referring to it as BNC but I don't think so. It's much larger.
@@TechTimeTraveller That may be an F type connector
The manufacturer of that keyboard for Tandy was the same one used to make the Dragon Data machines. It's not the same layout, but the board design in almost every way is identical including the font style. It's quite logical given Dragon Data machines were designed in tandem with the Tandy computers.
Oh, memories. I built a video terminal using the same Radio Shack ASCII keyboard encoder back in 1979 so I could get online nights/weekends when the timeshare system had no other users. Amazing dialup MODEM ran at 300 baud, much faster than the Teletype we had at school that was 110.
The rest of my setup were kits from Electronic Systems : a TV typewriter that was 16 lines x 64 characters, Power supply, UART board, RF modulator so you could run the video into a TV set, and a MODEM.
I have been looking for one of those Electronics Systems TVT boards forever. They just don't come up for sale. Probably because they look like random electronic junk.
@@TechTimeTraveller Sad to admit that I threw the entire board set into the garbage about 30 years ago when I got a VT100 and a VT220 from a past employer, because those were considered to be junk. The only value of the TVT board set is nostalgic, and most TVs could not display 64 characters very well because of their limited video bandwidth. I got nice results with a color TV by turning off the blue and red guns; the remaining green had no convergence issues. Blue-only and red-only worked OK, though not as visible as green. I had a smaller black-and-white TV, and it was actually harder to read than color (green). I did keep the Electronic Systems power supply for a few more years.
A year later I moved-up to a real 24x80 display (SD System VDB-8024), and that absolutely required a real video monitor, so the TVT got boxed-up and ignored.
The MODEM worked surprisingly well; very few bit errors even at 300 baud on standard telco, and of course that was with acoustic coupling (speaker and mic). Direct-connect was not legal.
I miss those days of real homebrewing. Hard to believe when you had 64Kbytes of memory, and a pair of 8-inch Shugart floppy drives you had a top-tier machine.
I wondered if the EPROM that had "nothing on it" was being used to clear the screen with some simple copy operations? Perhaps part of a bootstrapping circuit that isn't working?
16:34: the top of the screen be vibin'
The garbage on the screen looks like some kind of alien alphabet. I think it would make a great movie prop for some kind of alien/post apocalyptic sci-fi movie :)
Maybe this thing is a device for decoding the Voynich Manuscript?
@@michaelwright2986 or maybe it's the very thing John Titor (if you don't know who he is, look it up, but beware of the rabbit hole :)) was looking for :)
@@Bata.andrei Somehow, I missed him the first time round. And now the Time Cube only exists on the Wayback Machine, which is kind of too meta for words. I must read again Thief of Time, by Terry Pratchett.
Its a shame that the estate sale didnt keep the computer and the terminal together. That bothered me.
Yeah thats why I kinda rag on estate salers a little bit sometimes. They often don't take the time to research what they have (they can't.. they need to get stuff sold asap).. or they break up pieces to maximize $. The ones that break up mechanical keyboards and their machines because the keyboard is worth more by itself really irk me.
The Battletech nerd in me shivers when I hear the words “AC-30.” Just imagine…
OMG!! WASH IT!!! IT HAS SO MUCH LAND THAT YOU CAN PLANT SEEDS. SOMETHING SO COLLECTIBLE
When RAM dies, it goes to the Delay Line in the sky...
That wavy display is quite a funky sight, I'm guessing the video generator is having some trouble with timing on the horizontal blanking, but it's significantly worse in the first third to half of each field where it's jumping at a regular interval. I'll be interested to see if re-capping the power supply fixes that, or there could be something wrong with the crystal oscillator.
I'd be leaning towards an analog problem with whatever is used as a video DAC, making the sync voltage levels not quite right. Not knowing the circuitry it could be drifted resistors or a bad discrete transistor, possibly a chip.
Yep, the horizontal sync voltage level is probably not quite (low?) enough for the cheap TV, and the cheap TV is being cheap and its scan is drifting a bit. Find out where the hsync signal comes from, fix it, and it should become stable.
Oh, and there is no DAC because it's all digital, just a few different voltage levels switched by transistors and mixed together.
All those chips with 7430 stamped on them... I'm sure I had some like that came which from bulk packs at Radio Shack when I was a kid. But I checked my old chips and didn't find any. I did find a pair of 7440 chips with no other marking than the big white numbers, though.
With the other parts, it's clear that he got most of his parts from Radio Shack.
I even used three of those same boards/connectors to try to make an 8080A computer back in 1979. (It would never have worked because I didn't understand TTL fan-out, or even testing a subsystem at a time.)
I was wondering what the deal was with those stampings! Thank you! Yes I think you're quite right.. this really is a mostly Radio Shack machine.
This reminds me of fixing a Sharp Twin Fami 20 years ago! I got it super cheap "broken" and after months of tinkering off and on, I realised to my horror someone had replaced the belt, but had NOT marked the stack of analog gears when they took it apart and put them together randomly!!
After a lot of playing with it I finally got things aligned.
Then I put it away and tried to play it months later. I tried to play and nothing would work. The belt had rotted 🤣🤣😂
Eventually i got it working 🤣
Looks like some of those logic chips have milspec numbering on them.
I know not a whole lot about computers, but have you thought that maybe the computer it was built to hook up to (that got sold separately) was also modified and so they only were meant to work together?
Great video, and great channel you got going on here. The editing is charming and you're quite funny.
Many thanks!! Glad you are enjoying it.
gorgeous keyboard - reminds me of a BBC micro keyboard. Looks fantastic.
I saw that power supply and I was like.. NOPE!
I like how the best way to describe it is as computer “thing”
Wire wrap was awesome. BRING BACK WIREWRAP. 8:47 that's because it IS cardboard. Phenolic resin impregnated paper fiber, to be precise (modern pcbs use FR4)
Remembering from the old days, an eprom will hold its program for about 30 years, may give you some trouble.
It's not unusual for a cheap '70s terminal not to have a clear screen code. The CT-1024 did not, which is why the SWTPC monitor's "C" command sends a "home-up" ($10) followed by "erase to end of frame" ($16).
I love this channel so much. Fantastic content !
Many thanks! Glad you enjoy it!
Basically a modem terminal or a teletypewriter.
Those hand made breadboards are beautiful...
Really well organized I must say. Whoever built this thing knew what they were doing.
I have no idea of what i am watching, but i like the general vibes.
for the broken keyboard, maybe try placing some thin Hobby plywood behind it as a backer.
That rust was likely caused or promoted by pins and sockets with different metal compositions
apparently a lot of people skipped specifically to when the terminal's font was defined
then that must be one popular font then
as a person with schizophrenia, this is the best intro ever.
Maybe this homebrew terminal and the 8800 were put in the shed because the builder couldn't get them working right? I suspect this was an unfinished hobby project, based on the unsafe wiring and lack of a cover for it.
Great now I'm curious and want to see a follow up
Dude... love this project / vid / thing..
I'm watching this on a computer that I built thinking to myself "some dude in the future is going to buy my computer at an estate sale and pick it apart like this, wondering what I did"
That looks like a proper Cherry key keyboard, they were about £40 each in the late 1970s. Call it £400 now...
The +5V regulator is over there because you want it near to your board. Of course, they must have had to compromise!
See the little metal fingers? That's a Stackpole or HiTek type of key mechanism. Radio Shack used them in early TRS-80s, and they're also found in the ADM-3A terminal. They were quite nice to type on, as long as you had good debounce.
I hope the original builder of this or someone who knew them eventually sees this video and lets you know what its for. Maybe the modified system it connected to did something else. Could it be a cypher machine of some sort? Maybe im dreaming.