TRS-80 Model 1 test and teardown

#septandy #trs-80
On today's video, I'm taking a look at a TRS-80 Model 1 and matching monitor dropped off by Kevin, viewer and fan of the channel. I was told the machine should work -- but I always like to take a look inside and try things out first.
Part 1 of troubleshooting this machine:
• TRS-80 Model 1 repair ...
-- Video Links
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--- Links
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--- Instructional videos
My video on damage-free chip removal:
• How to remove chips wi...
--- Music
Intro music and other tracks by:
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@itsnathandivino

[@SchmeedIsMe]

@Adrian's Digital Basement ][, not burned out on TRS-80 content. In fact, would love to see come Coco content. 1, 2 or 3. Doesn't matter. Very fond memories.

[@michellelawson4267]

the very first machine I had was an S-100 homebrew version of the TRS-80 Model 1 Level II machine. The keyboard was a rewired version of the kit that SWTPC sold. The TRS-80 used a memory mapped keyboard. I used LDOS for the OS. I worked great. I also wrote a RamDisk driver program and had three 5-1/4" floppy drives. Brings back fond memories. Thanks Adrian

[@hernancoronel]

YAY! Another video on TRS-80! Love it, thank you!

[@rancidbeef582]

On my TRS-80 Model 1, the "T" key bit the dust after the warranty. I was around 13 or 14 at the time, so naturally I opened it up to see if it was anything obvious like a broken solder joint or something. No such luck. So I found there was a RS computer repair center in the town about 60 miles away. I got my mom and her friend to drive me there to drop it off. They quoted some amount (around $12 or $24 or something) to fix it. Not too bad. When I came back to pick it up a few weeks later they wanted more than that. The technician said they were charging more because "the warranty seal had been broken." I was like, "WTH, I'm not getting it repaired under warranty. What's that got to do with anything". So I asked to talk to the manager and told him my story. The manager told the tech, "you quoted him that price, charge him that price." I was so happy I'd stood my ground and didn't get ripped off for a stupid reason. One of life's lessons.

[@donaldhoot7741]

My first computer! I bought it with money from working at a restaurant. I quickly outgrew it when the C64 came out. Great video!

[@kjtroj]

Looking forward to learning what went wrong on that machine!

[@Blitterbug]

Thanks for having the courtesy (and knowledge!) to give the temp in Celcius in your story, Adrian. We haven't used Farenheit here for 50 years so I barely remember how it works, apart from 100 is supposed to be blood heat.

[@FritzPinguin]

My first computer! I had a 4k Level II, the one with the bouncy keyboard. Using it without KBFIX was almost impossible. Later I upgraded with an Expansion Interface and two floppies. NewDOS 80 was a great OS without perfectly working keyboard debounce. I learned quite a bit of Z80 assembly language on this machine. Patching and enhancing Scripsit was really fun! Thank You for bringing back memories!

[@StarsManny]

There was a 4k level II? I know there was 4k level I but I didn't know there was a level II 4k.

[@FritzPinguin]

@@StarsManny I bought it in Cologne, Germany. Maybe it was available in Germany only, I don't know. Not enough memory to load Star Trek (the Basic version), so I had to upgrade to 16k ...

[@ftorresgamez]

Our first computer!!! My dad bought the 4K Level I version from a Radio Shack in Laredo, TX back in 1978. One of the first ones! Wow, was it a piece of crap, especially that expansion card edge, or the interior seemed like it was built from a kit, but we LOVED IT! Well, we loved it just after my dad bought a few games for it in 1981 because before that we weren't that interested in it. I remember that my dad made a power supply for the computer and the expansion interface because he didn't trust the bricks that came with either, I think because they overheated or didn't have the power, I am not sure. He later bought two disk drives and a printer from Okidata. It was a very nice machine despite the usual things that ail it like the fact it wasn't very reliable - especially that card edge, or the fact that the three DIN connectors for power, cassette and video looked exactly alike. My dad bought us a VIC-20 after he had to take the computer for work but he didn't like it because the cartridges were very expensive (for the time) and so he sold the VIC-20 and bought us a CoCo 2 with the "melted" keyboard (this was before the version with the full keyboard started to appear in the market) but I was kind sad seeing the VIC-20 go because I had already written several games I found for it in magazines like Compute's Gazette and Compute! but the CoCo had Microsoft Expanded Basic... and my dad's friends had tons of pirated games ;-)

[@MickeyMousePark]

9:03 Fascinating the service label inside..(the RT line would be Repair Ticket #) serviced 12/17/79 which might be the time they upgraded it to Level II ...by 1982 when i started working for Tandy Computer Service Center those were no longer used..at my time we would write service center number (7XXX) and the ticket number on the warranty sticker.. Trivia: a warranty sticker that is white letters on black background is from the factory a sticker with black letters on white background is from a service center...

[@adriansdigitalbasement2]

Fascinating tidbits of info!

[@mikeuk666]

Keep up the great work Adrian

[@eTraxx]

My first computer .. loved it with it's 4K of memory

[@X-OR_]

The TRS-80 Model 1 (4K/Level 1) was my first computer. Put the computer on Lay-o-way at radio shack and spent 6 months mowing and raking peoples lawns until I was able to take it home. I still have my TRS-80 in the box.

[@andrewdunbar828]

This was the very second computer I programmed on, in early 1980 I think. I used to be able to walk up to any TRS-80 I/III and type in a "dodge the obstacles scrolling up the screen" game. The first computer I programmed on was an Apple II where I spent weeks typing in a similar game and days debugging it. I first became aware of the existence of machine code and assembly in the TRS-80 days but didn't actually use it until a couple of years later when I got my Spectrum.

[@xlerb2286]

Back in the early 80's Radio Shack used to sell some perf boards with a 50 finger header on one end. A buddy and I used those to make a bus and card cage for his TRS-80 Mod 1. We extended the memory, hooked up a Z8530 SCC, and a few CTC (counter timer controller) chips which we used to build up some computer controlled lighting systems. I think I've still got some of that hardware (but not the computer) stored in the garage.

[@muttBunch]

Can’t believe a year has flown by that fast for another Septandy. Jeez we’re getting old ❤️

[@fltechie]

Ahhh Memories. I worked for the Tandy Service Center in South Florida in 1980 - 1996. I worked on many of these units and installed many upgrade mods. The Model 1 was not the easiest to work on.

[@MickeyMousePark]

very cool...i worked at Tandy Service Center in Santa Rosa CA 1982-1986..

[@IanSlothieRolfe]

My first ever job working for Marconi Avionics during the summer break for University saw me using a TRS-80 Model 1 - They wanted to use it to capture data from their minicomputers and draw graphs etc. I was tasked with writing a terminal emulator with hooks so that the data could be sent to floppy disk and then used by other programs to be run on the TRS-80. I had once written an assembler program on the schools RML 380Z so I had told them I knew how to program Z80 Assembler... so they gave me the job! Quite a steep learning curve but I got it done, and they were pleased with the results! At first we didn't have a TRS-80 assembler, so I had to assemble to code on a minicomputer and transfer the hex files over to the TRS-80 with a simple serial download program I'd written in BASIC. When my boss saw how fiddly the process is he "acquired" a TRS-80 based assembler from somewhere and that speeded things up somewhat. I was quite impressed with the TRS-80 and quite wanted one, but I had a PET 2001 at home that my Dad bought for the family (realistically, me and him!) which was as good to my mind (despite not having a floppy disk) and the TRS-80 was very expensive by comparison here in the UK.

[@andrewpaige316]

Happy Septandy!

[@shadows9001]

Yes! Love these computers. Would love to get my hands on one

[@zaphodbeeblebrox1695]

I have one, with the green screen monitor..... my precious :D

[@robertlawrence9000]

Whoa!! That's an awesome looking system!!

[@jeromethiel4323]

One of the best modifications you could do for the model 1 was to get a set of gold edge card connectors and solder them to the expansion port edge card. The original edge card connector was famous for corroding and causing intermittent connections to the expansion interface. I have a couple of TRS-80 model ones with that specific modification. They were very common and advertised aggressive in TRS-80 hobby magazines of the time. Another easy mod for those who could not afford the expansion interface was to piggy back and solder into place an additional 16K of ram chips onto the existing 16K chips except for the CS line, and then bend that pin up and solder a single wire to all 8 chips, and to one of the address decoder chips, to allow 32K in the base chassis.

[@melkiorwiseman5234]

I'd expect that someone enterprising enough would be able to "triple-decker" the chips to add in the full 48K, presuming the case would still fit over the chips.

[@jeromethiel4323]

Such a soft spot for the TRS-80 model 1, because that was my first computer. Not the fastest, but not bad for a budget machine.

[@rancidbeef582]

Man I loved my TRS-80. I bought a Basic programming book about a year before I actually got it. I wrote tons of code for it before I got the thing! My folks gave me a choice of a computer or a new motorcycle (mini bike actually)... they were priced about the same at the time. It was a hard choice, but I think I made the right call as it's led me into lifetime passion and career.

[@SenileOtaku]

The Model 1 was my first "retro" computer (picked it up out of the attic in a Catholic school, along with three Model III machines) and was the last one I sold once I sold off my collection (I still have the two TI 99/4a machines that haven't sold as yet). Mine had the expansion interface, monitor and two disk drives. It was amusing to see the patch someone had done on the monitor cable, where they covered a split in the outer insulation with an adhesive bandage (yes, an actual generic-brand "band-aid").

[@dementedpeep]

TRS-80 video's are so satisfying

[@TimSedlmeyer]

TRS-80 Model 1 was the 1st computer I used. It didn't have the official lowercase mod but my dad did implement the Electric Pencil lowercase mod. I learned basic electronics and soldering helping my dad build the LNW expansion kit. We scoured local HAM fests to gather all the needed parts.

[@johncasteel1780]

Avoiding the Expansion Interface (Tandy took three tries to get it right), I also built up an LNW Research board. I used sockets on mine. My board came up with *zero* soldering problems. OTOH, I also mis socketed two RAM chips. I built and tested the board in sections For an OS, I settled on DOSPlus.

[@retrozmachine1189]

I'm amazed those spacers are still flexible. When I had original series Model Is come in for repair in the mid '80 it wasn't unusual to find the spacers already going hard and starting to crack.

[@adriansdigitalbasement2]

Interesting! My other machine they are rock hard and cracked -- so yeah I was super shocked these were still pliable and supple.

[@melanierhianna]

I have a model 1 which was my fathers and it’s a level 2 16K one with a keypad. It’s still in the box. Interesting it has the security sticker broken but we never opened it. In the UK we often got them with RF modulators and not monitors. I’m going to do my own Septandy and check it out.

[@8BitRetroJournal]

You're a day early. This is my dream TRS-80...first computer I ever got to use regularly.. I have a dual floppy model 3 which is nice, but doesn't hit me the same way as this one.

[@adriansdigitalbasement2]

Let's just call it early access :-) You know while this machine is historical, the Model 3 really is a better all around machine -- and also totally compatible. So, if I had to pick one, I would go with the M3. Of course, I have the luxury of choosing since I have both.

[@paulstubbs7678]

Nice to see the innards of an early model 1. I bought a TRS-80 Level 1, 4K, then had it upgraded. Thankfully mine was a later revision and they didn't have to add the 3 rom piggy back board, and they also upgraded my keyboard to the numeric keypad by replacing the whole keyboard, as in mine is one complete assembly, no tack on side pad. So working on it is way easier, no bodges, just the main board and the keyboard. I swapped the 4116 ram's for 4164's, so all my ram was on the main board, rather than having 32K in the expansion box. This gave a more stable system, as the interconnect cable was problematic, especially when things get hectic like during an active game session, with the keyboard section getting moved about etc. I later rebuilt the whole system into a brand new model 4 case, ordered as a spare part.

[@jonathan_herr]

That's quite the intriguing tale!

[@thebigt42]

This is the first computer I ever used (1978). My grandfather taught me Chess, Blackjack, and a little BASIC on it.

[@timothyp8947]

Until seeing them in recent years on KZbin retro channels, I had always assumed the original TRS-80s (now known as model 1) were three box machines - they were always pictured like that in UK computer magazine I read (PCW) and the only time I actually used one in a class (guess I was around 13) they were also 3 box units. It came as quite a surprise to find from things like previous 'Sept-Tandy' that the model 1 main computer was in the keyboard.

[@paulstubbs7678]

When you started out, you had just the keyboard part, then later on you added the extra's as money permitted etc. If you were happy with 16K and cassettes, then the keyboard part was all you really needed.

[@timothyp8947]

@@paulstubbs7678 yes, I can see (now) that this is the design… but I wonder if they were sold like that in the UK - I don’t remember ever seeing an ad for a TRS-80 that wasn’t showing a 3 box machine… not that I would ever have been able to afford any such a beast on pocket money, so I’d never have looked beyond PCW adverts & articles.

[@rancidbeef582]

I guess that's the expansion interface? I never could put together enough coin to get one of those...

[@jonathanwhiteside6092]

Very interesting to me, as I'm currently repairing my own TRS-80 Model 1. So far I've found quite a few issues with power, the clock IC was dead (Now replaced) and I can boot to the screen with all the garbage :). I've just found another dead IC, the decoder/multiplexer at Z21, so waiting on parts for that now. Love your work, looking forward to the repair video :) BTW I have the 8 bit video RAM for the lower case conversion, but only 2 ROM ICs at Z33 and Z34, will your diagnostic ROM work with this version?

[@RS-ls7mm]

This started it all for me. I was about to buy the TI programmable calculator until I saw the first ad for the TRS-80. I bugged the Radio Shack manager so much that he gave me the store prototype (serial number #22 I think). At first it was just software but soon that wasn't enough. The extremely good technical manuals taught me a lot. I modded it so much no one would recognize it as a TRS-80 now (Its all rack mount now). Doing Arduino/Raspberry is a close experience but lacks the newness and excitement this had back then.

[@paulstubbs7678]

I did likewise, I put mine all into a 19" rack case, with the keyboard box just holding the keyboard. Later I tired of this and rebuilt it all again, this time including the monitor, into a model 4 case ordered as a spare part from the Tandy/Radio shack service centre.

[@RS-ls7mm]

@@paulstubbs7678 I never got tired of the rack mount since it allowed for all kinds of expansion cards. When the time came to upgrade I went for an Amiga. Apples were basically non-existent where I was.

[@StarsManny]

Do you still have it?

[@RS-ls7mm]

@@StarsManny Sadly not the original motherboard, they grabbed it when I upgraded and gave me a later board. They claimed the old board wasn't compatible with the upgrade. But I think the case still says 22.

[@danaeckel5523]

First computer I ever touched was a TRS-80 model 1. It was my uncles and I inherited it few years ago after he passed. It did not have the number pad, and started out as the 4k level 1 basic. He expanded it along the way so it has the 16k level 2 basic. Unfortunately I never see much online about these systems. I would love to see a modern remake of the expansion interface so I can try to get more out of this system.

[@jeromethiel4323]

You can find the original expansion interface on e-bay. I found a couple years ago, and i bought them sight unseen. Wanted that expansion interface so badly, back when i was a teenager. Not for the floppy drive interface, just for the extra ram! 16K is just too small for really good programs.

[@tinyBigGAMES]

😮Wow, this was the very first computer I ever owned. My parents got this for me at my local Radio Shack, way, waaayyy, back in the day. It was the Color Computer that I got next, on which I learned how to really program and set the stage for my future computer endeavors. Good times, good times!

[@sprybug]

Yee! First computer experience was a TRS-80 CoCo 2 in 3rd grade. Then a TRS-80 Model III in 4th grade. My first home computer I bought with my own paper route money was a Tandy Color Computer 3. That was really the start of my computing expeditions there!

[@tinyBigGAMES]

@@sprybug We had Model IIIs and Apple IIs in high school computer lab. Yea, the CoCo was nice. I learned so much from it. I ended up getting all of them 1-3, hehe. My first MS-DOS machine was the Tandy 1000. Ahh, watching this video brought back some fond memories.

[@greendryerlint]

While the first computer I programmed on and owned was a Commodore PET, my first hands-on exposure to a microcomputer was a TRS-80 Model I at a local Radio Shack. Being a nerdy, techy kid, Radio Shack was to me like a candy store might be to another kid. And the manager at the time was easy going and indulgent and didn't care if me and my friend sat down and played games on the Model I. Perhaps he thought it was a free demo of the machine for customers. I remember happy hours playing text adventures on that thing. While the PET is still a favorite of mine, it was the TRS-80 that gave me the computing 'bug'.

[@normantyson5314]

I was working as an electronic tech at the time Tandy produced the model 1. At the time it was so tempting to buy a computer, but there were advantages to buying the Pet, or maybe an Imsai processor. Radio shack just came on the market, and they had one in the front of the store. No demonstration, no instructions. I started pecking on the keyboard and getting error codes, until a salesman came over and told me I couldn't continue. I then selected some components and printed circuit material. Asi paid for my purchase I told him that until he ran me off I might have been interested in the computer. I then went to another radio shack and made my purchase of a model one, level two machine. There was a hobbyist magazine and a great forum of projects to expand and improve the machine. Also the construction of the LNW expansion along w/ floppy drives and then the TRS-dos followed by LDOS operating system. It was all so satisfying to determine what was necessary to make it perform like the big guys.

[@craftsman123456]

Need to find one of these

[@ernstoud]

Ah, my first computer. Still sitting in my study. Biggest hobby was breaking copy protection of software games. Whole community here in The Netherlands. The extra mode is to improve data communication to the tape drive.

[@EddieLeal]

Oh the nostalgia. Our high school used these computers for a BASIC programing class. Only our computers were the model 4 if my memory serves right. They had the floppy drive built into it along with the key board. I failed this class miserably. I guess it helps when you actually attend all the classes. 🤷🏻‍♂😉😁

[@TheSimTetuChannel]

Now I can't wait for a PDP-8 restoration on #DECember 😉

[@retrozmachine1189]

The regulator circuit on the Model I was pretty well done and would go into protection if there was a short on the output or over voltage but there is a weakness to it. If the pass transistors fail, especially the 2N6594, there is no additional effective protection to stop the TTL ICs etc from being fried. After some 40 years those power transistors can just give up the ghost and fail shorted. A simple crowbar circuit on the outputs along with a fuses inserted in series with the outputs will protect the rest of the TRS-80 from overvoltage if that transistor ever does fail.

[@paulstubbs7678]

Not good, maybe time for me to lose the linear supply and fit something else. I had been using the thought 'keep it original', a bit of a joke in my case as it has seen SOOO many mods it's not funny (it now all lives in a model 4 case!)

[@rancidbeef582]

Good to know. The main reason I haven't tried powering up my old TRS-80 (and Commodores) is because I put the cables and power supplies in some random box somewhere and I haven't been able to find them. That may have been a blessing as I probably don't want to actually use those old supplies...

[@agranero6]

I worked on a Model I for a few years on my first job as a programmer. I never saw the insides of it, just of Model III. A little underwhelming, I thought they were better made. Thanks.

[@davefiddes]

Looking forward to the repair video. Bet the loss of video is down to the 74C series chips RS used to generate the video sync signals. They are fragile and go bad.

[@adriansdigitalbasement2]

You'll only have to wait until this weekend as I'll be putting the repair video on the main channel :-) I had suspected those blasted 74C chips too.

[@WackyT08]

I think 'supple' is right up there with 'moist'. LOL!

[@timsmith2525]

That machine looks new! Too bad the video crapped out. The Model I was the first computer I ever programmed.

[@KevinBerry]

Heh, one of my earliest memories at age 2 was plugging the AC into the tape port, and the smoke came out. My dad was not happy heh.

[@richfiles]

I picked up an old TRS-80 Model 1 when I was a kid... It had the memory expansion box, and two floppys. I *very much* regret getting rid of it.

[@stevencarlson5422]

Adrian you should pull out your other one and just show how rough it is and what you had to do, it be an interesting video

[@normantyson5314]

The small add on board was a mod that Radio Shack came out with to improve the cassette interface. I think essentially it was a schmitt trigger add on that shaped the audio pulses. Otherwise, sometimes it was hit or miss whether the download would finish w/o errors. They provided it free, and the dealer that I bought from handed it to me so I could install myself. He was otherwise provided the labor at his expense and was glad to save on tech time. The other thing the expansion interface would provide was the real time clock. Unfortunately, since both the clock and the floppy disk interface shared the non maskable interrupt feature of the processor, repeated floppy disk accesses caused the RTC to loose time.

[@adriansdigitalbasement2]

Oh that's really interesting! Good to know. I guess they must have cut at least a trace to wire this in?

[@keithjackson1180]

@@adriansdigitalbasement2 I am guessing that is what the repair sticker just below the space bar was for. It said 'Cass Mod ' in the service spot.

[@melkiorwiseman5234]

According to what I've been told, the cassette interface worked by recording either a single pulse within a certain time for a zero or two pulses within the same time for a 1. The read routine would look for the first pulse, then wait a certain time before looking to see if there was a second pulse in order to determine whether it was a zero or a one. As I understand it, the original BASIC interpreter had a fault in the cassette interface routine such that the timing for reading the pulses did not exactly line up with the timing for creating them in the first place. This meant that the interface could sometimes read a 1 as a 0 when reading from a cassette. A later revision to the software adjusted the read routine to correct the timing, which fixed the issues with the cassette interface.

[@ernstoud]

Yep. That is it.

[@Obi1kenobi10]

I STILL have and use a TRS80 4-P. I 1st learned to program/code on a Tandy.

[@michaelcloutier2225]

This system was my first wholly owned computer. I had a internal 48K memory upgrade and a Hires Graphics mod that allowed you to modify every character matrix to make pretty good looking graphics by tiling them together to simulate a bit mapped mode. I also had a CPU multi speed upgrade that let you toggle 3 speeds to I can't remember how fast. My mass storage of choice was a exatron stringy floppy that was a continuous loop tape system like the Sinclair QL wafers. I had to learn a lot because off the Model Is several limitations. It was a great system.

[@adriansdigitalbasement2]

Those were period mods I take it? it sounds fancy!

[@michaelcloutier2225]

@@adriansdigitalbasement2 There were mags just for the TRS 80 and there where a lot of amazing mods by mail order and all hand made. I sold if for twice what I paid for it new.

[@MrStevetmq]

Thats the first time I have see the keyboard split like that. The three Model 1s I had, had the numberpad and keyboard both on the same circuit board.

[@frankowalker4662]

I grew up in my pre-teens with Sinclair computers, but I still miss my Model I Trash 80 with Model II up-grades I had from 86-90. I have an emulator, but it's not the same.

[@tigheklory]

I really can't wait until you get a Coleco Adam, the predecessor to the MSX. I want to see you react to all the flaws in the design and what you do to address them.

[@8bitwiz_]

I tried to get my old TRS-80 running a few weeks ago, but the video sync was all bad. I did a quick search for info and apparently there are three 74Cxx chips in the sync generator that I should check first. And then I found a bare TRS-80 board (no keyboard attached) in my garage, so more on my "to-do" pile.

[@MrEd-qg8td]

The small board is the XR mod. Has to do with improving and stabilizing the Cassette audio.

[@ghohenzollern]

Now that I've seen your videos on TRS-80 Models 1, 2 and 3, I'm confused about the TRS-80s we had in school when I was a kid around 1984. There were two of them and they had been donated by a parent of one of the students who worked for a computer company in my hometown. My memory was that one was referred to as a model 1 and the other as a model 3. However, they both were in a case with a built in monitor and drive bay like your model 2. Instead of one 8" floppy drive, they each had two 5" floppy drives built in next to the monitor. I wonder what the heck they actually were. I remember we had some games on a disk, and the ability to program in basic. I remember a few games we had on it. One was I believe called "Firefox" and involved flying a bomber plane over a city. Another was called "Oops" and involved making your way through a maze where the path through would change as parts of it moved left and right. If you hit a wall, the screen would clear and display "OOPS" written in large letters. A third was text-based and called "Dungeon" and involved random encounters on your way to defeat a wizard in a dungeon. You would be prompted with various multiple-choice decisions on how to respond to these encounters. One random encounter I remember read "You jumped an orc scout troop and knocked the stuffing out of them." I also remember that the basic programming language we had access to I found impressive because it had the ability to add an ELSE clause to an if-then statement, which the Basic on the ATARI computer we had at home did not have. Does any of this ring a bell for anyone else? Any guess as to what model of TRS-80 we actually had at school?

[@ghohenzollern]

Oh and I remember there was a problem with the operating system that they each used being incompatible, but it was a matter of a magic byte value somewhere on the disk that got checked, and if you could change that, then disks from one of the machines could be used on the other. Or something like that.

[@kevin34ct]

I had a friends father that had a TRS-80 Model 1 and he added an Atari joystick to the computer by hotwiring the wires from the joystick directly to certain keys on the keyboard. We used it mostly for Summer Games? I think that was the name. It made running sports much faster than pressing the keys on the keyboard and was less stress on the keyboard. After a while we took the rubber grip of the joystick and added a weight to the top. This way you could flip the joystick upside down and wiggle the joystick to run even faster. One Hundred Meter Dash in less than 2 seconds.

[@rager1969]

I bought one of these with the expansion bay and disk drive for $100 about a year ago. It's filthy and was stored in a garage or shed in a plastic bin, but the lid wasn't closed. I never took it out of the bin because I saw a black widow spider crawl out of the bin (that was in my car?!) So it's just sitting in my garage, as is in that bin. I'm guessing it may be safe now to root around, but then again. I'm not sure what I'm going to do.

[@johnsonlam]

Rescue is not always straight forward, but it's challenge.

[@davefiddes]

The other reason for the 5V on the video out is to power a modulator. My UK spec TRS-80 came with a modulator in a little ABS box looking a bit home made (but was apparently factory) so it could get hooked up to a BW TV. Fancy monitors, expansion interfaces and floppy drives were confined to the Tandy catalogues being a bit beyond my pocket money aged 6!

[@adriansdigitalbasement2]

That makes sense -- I figured as much. They basically put the RF modulator inside the US monitor (although it's not outputting RF) it's still powered by the isolated supply in the computer.

[@senilyDeluxe]

(I'm not sure of this, I only fixed the German version that had a step down transformer) The monitor is a hot chassis and in order to not connect the computer to mains voltage, the computer uses an optocoupler to get the video signal into the TV.

[@muttBunch]

And hopefully we will see another Tandy 1000sx. That’s what I started with at 6 years old 😢

[@monomonster]

The first comp I used. Owned by one of my high school teachers. I learned BASIC on it and an Apple ][+. The TRS-80 had 2 disk drives, and the Apple had only a cassette drive. 😁

[@grantfryer1]

Looks like you may be able to replace the bad spacers with rubber tubing cut to length.

[@Robin_Nixon]

My first computer - I programmed the heck out of mine!

[@robertlinder6414]

Bring back the days of a college freshman

[@marc6340]

This was the first computer I ever owned. Payed for it with money from my paper route! I believe it was about 400 dollars! For a kid in 1980, that was a lot! I could have bought a car with that! I still have the computer, in its original box, and it still works. The keyboard developed a nasty skipping problem (you would hit one key and it would put a dozen characters on the screen). Only thing missing is the little door over the expansion port. Still love it, though!

[@jmac8092]

Put Silicone grease inside the key caps after cleaning the contacts.

[@StarsManny]

The older models have a famous keyboard problem where you get more than 1 keystroke sometimes, although I never knew it was as bad as you described. There's are "de-bouncer" fixes for it in either software or hardware. If the keytops are smooth then you know you have an older keyboard.

[@garyjohnson4608]

Adrian, can you suggest any books I could obtain to use as reference while I learn to build / repair 8 bit computers ?

[@NerdlyPleasures]

Interesting, I didn't know there was a variant of the extended keyboard which had the keypad with Stackpole switches. My Model 1 has a single PCB for the keyboard and keypad and uses the Mitsumi switches throughout.

[@adriansdigitalbasement2]

Oh interesting! I have only worked on two of these and both had the stackpoles like this. It's so hilarious how the numeric keypad is just soldered to the switches on the main PCB.

[@lukeeyeamyourfather3488]

Computer I learned on in 1984! We called them Trash80!

[@definitelycasualpcs8789]

Hey adrian. I picked up a level 1 model 1 a few months back and been itching to restore it. Any advice for possibly getting software to it? Most software I've found online or modern solutions call for later level 2 model 1s

[@johnhunt1725]

You broke it right in front of our eyes LOLZ!

[@startedtech]

I need to fix my TRS-80, the monitor has a weird shakiness that I guess is caused by a bad cap or two in the power supply. Also I can never figure out the disk drives consistently, but having three aftermarket ones probably doesn't help things lol.

[@kencreten7308]

But, but... that was too short! heheh. Great video. Thanks.

[@sideburn]

The first computer I saw and wrote a “hello world” BASIC program on and was hooked. Santa brought be a coco for Xmas and I was thinking “where’s the rest of it!!??”

[@melkiorwiseman5234]

I'm presuming you re-wrote the diagnostic ROM according to my suggestion so that it no longer requires a stack? Good work!

[@adriansdigitalbasement2]

Yeah check out the github repo -- no more RAM stack used at all.

[@melkiorwiseman5234]

@@adriansdigitalbasement2 I've done programming all the way down to the binary level so I understand how difficult programming without a stack can be. Once again, to all who worked on that program: Good Work!

[@paszTube]

My model 1 has cracked spacers, does anyone have tips how to replace those?

[@SimonEllwood]

Now we know where the Acorn Atom design came from!

[@rancidbeef582]

That little circuit in the TRS-80 video monitor that needs 5-volts is an optical isolator. I made a video switch box so I could use my older TRS-80 monitor as an 80-column monochrome monitor for my Commodore 128. and I had to hook it to a 5-volt supply just to power that optical isolator. I think the Technical Reference manual for the TRS-80 must have had that circuit schematic in it... otherwise there was no way I would have figured it out... WAY before you could just "google it"!

[@fyreantz2555]

I remember Tandy sponsored a DC comic with Superman! Two kids learned how to write programs to help Superman use his heat vision or some such. 10 year old me thought it was KEWL.

[@TheTkiller9999]

WOW that must be a really old Model one..... the model one I had... it had the side num pad included on the keyboard (a metal cover ) the little board looks to be the Lowercase mod. to get the spacers out... twist the spacers on the post that free's them up so you can just remove them easily

[@SharkoonBln]

Does the video signal come back on the connector if you unplug the monitor? Just basic troubleshooting, VID OUT left the building as soon as I plugged the monitor in, how about I unplug the monitor? 🖥

[@ericpaul4575]

Yeah it could be too much load for the output and bringing the signal down to zero.

[@esra_erimez]

The TRS-80 Model 1 was my dad's first computer when he was a kid.

[@roblatour3511]

This was my first computer too, no upper case for me though.

[@cairsahrstjoseph996]

That truck story is so funny

[@michaelblair5566]

My first computer was a Commodore VIC 20.

[@jmac8092]

TRS-80 Model 1 mods, silicone grease on the inside of keys, hard solder connection of the console to the add on 64 k memory console, install the switch on the character chip to enable the alt character symbols. Also you can replace the boot room with an eprom containing 'cpm'. Original 'Donkey Kong' concept programed in the program printed in magazine 80 northwest magazine. Original 'tic-tac-toe' program characters used before the ninetendo character switch to the 6502 chip. Senior Field Field Engineer, PRC Corp.

[@c1ph3rpunk]

The TRaSh-80 got a bad rap back in the day, I always liked it.

[@tekvax01]

the little mod board is a keyboard key repeat keypress mod. If I remember correctly.

[@freednighthawk]

Personally, I'd replace those spacers with silicone tubing. Just measure the posts they go on, and you might be able to find something suitable at someplace like Lowes or Home Depot. Just use a nice fresh razor blade to cut them.

[@johanlaurasia]

Adrian wins the earliest Septandy Award....lol

[@adriansdigitalbasement2]

I red-lighted the launch!

[@chadhartsees]

WOW.

[@waynegoodwin3217]

Hi Adrian, can you please let me know the make/model of that chip removal tool you use on today's video, the one that looks like a screw driver.

[@adriansdigitalbasement2]

It's a Wiha Chip lifter -- not sure the model number beyond that.

[@waynegoodwin3217]

@@adriansdigitalbasement2 thanks Adrian I found one on ebay,

[@physnoct]

It would be interesting to use the audio debug port as a modem to get diagnostic messages.

[@adriansdigitalbasement2]

Would be possible if we treat it as TTL-Serial.. Only issue is it has a couple levels and none are TTL, so a level shifter would be needed to bring it up to 5V -- perhaps a single bugger would work.

[@worldgate989]

i had one of the units that was all in one, everything one piece, and i ended up throwing it in a dumpster because it was so old. still worked and regret it to this day

[@robtaylor2045]

Consider sending me the field found PCB for replication. 😁

[@jonathanwhiteside6092]

Also interesting, mine has a one piece keyboard and numeric pad, and the keyboard layout is identical to the Dragon 32 albeit the Dragon doesn't have the numeric pad.

[@adriansdigitalbasement2]

Yeah it's funny -- seems this two piece design (aka afterthought is the rare keyboard setup)

[@jeffreyphipps1507]

I think I'd do what you did before - make the keyboard removable by making it a ribbon cable with pins to remove it. The other wires on the mod could be made into a similar set of wires that are detachable? I'm never a fan of non-detachable wires.

[@uni-byte]

Back in the day we were expected to take responsibility for our own f'ups. I miss those days. Hey, if you waited a day, you could have submitted this under SepTandy!

[@falksweden]

It's September in Australia :)