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- Опубликовано: 14 окт 2024
- Dave looks inside the most popular microcomputer of the 1970's, the Radio Shack / Tandy TRS-80 Model I
And also a look at the TRS-80 Model 102.
Bonus EMI testing for fun.
Bonus rant on how slow the Tektronix MDO3000 is in RF mode.
TMS4116 16Kb DRAM:
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Level II BASIC Reference Manual
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Yesssssss! The first computer I ever used!
The one I got had bad RAM that degraded slowly. What I saw as it failed got me to quit smoking weed. Mind bending graphics.
Weeewuh!
sounds like my specs
First computer I had. Learned Basic and assembly programming on that thing. The cassette backup was a bitch.
Same here, this was my first machine, had the 12k expansion as well, a whopping 16k, as soon as this title crossed my screen i went to the vid, I needed to do a walk down the computer lane there :)
Myself and 2 friends used to go to a Radio Shack in NE Philadelphia and load our programs and play with the display model TRS-80 in the store on Saturday afternoons. The store manager and salesman loved us because we were doing much more than making "hello" print 3000 times. We had a very cool ASCII Star Trek game being programmed. We would save our program and bring it back the next weekend to continue. The manager would love to show case us when "parents" came into the store. It was hilarious but it was so much fun!!!!
Now 42 years or so have slipped by since I worked a one of the largest Radio Shack stores in the US in Framingham, Massachusetts.and we were certainly excited to get these units into the store and they did sell as fast as shipments arrived. As I remember the story, the computer was first going to be sold as a kit that you built by yourself. After meeting with the brass in Fort Worth, it was decided that it would be better to sell it as a complete unit. Two things I do remember differently than you described. First, the unit was shipped to us and sold with the keyboard and the "video" screen and the tape recorder and the power supply with all the cables. And it was all included in one box for the price of $599.00. And second, the first units only came with 4K RAM but later units could be ordered with 8K RAM. As you pointed out, it was a rapidly changing market so updates and changes came rapidly after production started. I have a slight difference in the clock speed. You stated that the speed was 1774 however the joke at Radio Shack was the speed was 1776--remember this was right after the 200th anniversary of the founding of the US. This computer was incredibly slow. Basic did not help. As a test, a friend and I wrote a program to sort 100 peoples names. Several hours later it was still working. But having said all of this, I remember staying up all night playing with the computer that I borrow from the store over the weekend--Stores were closed on Sundays back in those days. I learned a lot and I also sold many units Thanks for the program that you put together It was fun to watch.
That machine had daily use as a home and business computer for 6 or 7 years. The next 2 or 3 years it got flogged in a factory as a label printer driving a sequence of dot matrix printers. Then retirement and storage once PC clones took over. There was no bootup time so the easiest way to stop what you were doing and get ready to load the next task was to power cycle. Flicked on and off all the time.
Primarily used for word processing (note scripsit labels on keys) and label printing using custom apps written by family members when it was at work. Had the same plus games plus VisiCalc at home. Also used for writing a lot of random games, apps, and utilities as I learnt to program.
Had 1 game with sound. To get the sound you had to connect up the tape player, Set it to "Record" and hit pause which would cause the sound input to come out through the speaker. Even then, it was more squeaks than sounds as they were produced by writing out certain bytes combinations via the tape interface that were known to produce alien like sounds. Squeeks and squawks only.
Ben Govett Awesome, thanks for loaning it Ben!
The Heath H8, also introduced in 1977. Spent many hours looking at that page in my catalog. Spent many hours looking at the TRS-80 page in the Radio Shack catalog too. The first computer program I ever saw running was written on the spot on a TRS-80 model 1 by the sales clerk. It printed my name in a zig-zag pattern on the screen. Of course, I was hooked, and programming has been my profession.
I love how the comment section is full of nice stories like this!
040 100
I never tire of reading these nostalgist stories!
Brings back memories! I worked as a service tech between 1978 and 1983 in an independent Radio Shack dealership (actually two) in Slidell, Louisiana before Radio Shack (later Tandy) clamped down and only ran company-owned stores. I remember the owner successfully winning a lawsuit to remain an independent dealer/repair station per his contract. Needless to say, Tandy hated us :)
You are right that the expansion cable leads to the Level II ROM. The original ROM chip was pulled out and the expansion board attached with double-sided tape. The colored jumper wires were attached for power, etc per the Tandy-supplied instructions to the techs. Oxidation on those jury-rigged connections caused no end of grief.
Little known fact: When we had to replace or upgrade a DIP chip in the field, we were required to socket it to show it's compliance with the latest update. PITA because some were used in moist environments and the tinning on the chips would oxidize (like you see on the Z80).
Later, when the FCC cracked down on emissions, we were required to add stick-on shielding packs to any Model I, II or III that came through the shop whether is was part of the repair or not.
We had tons of fun (not!) in fixing the circuit board design errors on any early-model machines (usually the II or III models). It seems we were forever getting service bulletins to cut this trace, jumper from here to there and generally create a rats nest of circuit fixes that should have been found in the original circuit boards.
All in all, pretty sturdy machines that would get pretty warm over time and sucked power like it was free. I never liked working on the monitors much since I got knocked unconscious once after accidentally running my right forearm across the back of the cathode ray tube doing a repair. My tech buddy said it tossed me about 6 feet back from the tech bench. Don't remember that but DO remember waking up on the floor. I still cringe every time I see an open flyback transformer...
"I never liked working on the monitors much since I got knocked unconscious once after accidentally running my right forearm across the back of the cathode ray tube doing a repair."
And that is why, folks, I don't do monitor repairs.
Yes, you learn the value of an isolation transformer Very quickly! I went in forgetting to plug in the monitor into the transformer with my scope pro, flew across the Room and messed up the probe as well
You know, back in the day, sound on the TRS-80 WAS an AM radio! You turned into the noise the computer makes and some of the games were programmed to cycle the processor just right to make sound effects and music!
Right, the AM interference was a feature, not a bug.
My Dad drove me to the Radio Shack and paid $875 on his credit card for 16K Level II BASIC TRS-80 Model I after I begged him and promised to pay him back. God bless him. My poor father is dead now and I am a professor of computer science at a major state university in the United States. Thank you, Dad!
I still have my Model 1 with 16K (serial #6841). I piggy back soldered a memory chip into the system to access lower case letters (with a toggle switch to disable for some incompatible programs). I taught myself BASIC and then was allowed to teach a 9 week class in my senior year of HS in 1982. This device gave me the jump start in the computing industry and a boost to my confidence at a very crucial time in my life. Thanks for sharing and taking me back to my roots!
I used to work on these back in the 80's and i still have one that i must restore to life one day . Back in the 80's i made a load of hardware and software for them, i never marketed / sold it though :( . Audio samplers, 512k ram extension , RAM based NEWDOS/80 (no need to load overlays from floppy/HD) plus much more.
I pre ordered mine in early 1977 serial # 004. Wish I kept it, would be worth a fortune today.
+Dan Todd Wow, serial number 4!
I traded out a early one with the flat keys and kkkeybounce (no keypad) with a 35 track shugart for a newer Model I. Good idea at the time, not now though. :-)
Had to load the debounce TSR. I remember it well.... I'm old too.
Early adopter? I wish i kept my Commodore 64... still have the box
+Foxy - You could sell that box on EBay to someone who has the computer.
It was actually possible to get a TRS-80 Model I without the numeric keypad throughout most of its production run -- not just the very early ones -- if you bought the low-end 4K version with Level I BASIC. The 16K Level II version came with the keypad as standard. It was also possible to upgrade the RAM and the BASIC without adding the keypad, so once in a while you'll come across a Model I with 16K and Level II but no keypad.
I first learned computing on TRS-80s back in the early '80s.
That was a great computer.
Dave, that was awesome, and beautifully filmed too (love those macro shots). It was 4 years ago I found your channel when you did a teardown of your old Tandy 1000 (EEVblog #32)... and I just found my old comment on that video! I had no idea back then that this would be my favourite channel on RUclips. Good on ya Dave.
Thanks. Wow, yes, the Tandy 1000 video, that was a long time ago in a galaxy far far away...
Started my engineering career working bench for Tandy in 75 through 82 and designed the serial to para I/O board that was used when they replaced the Cassette with a Shugard 5 1/4" floppy drive...
Paul Mays Hey I have a trs-80 model 3 and I really want it get it up and running so I was wondering if you could help me?
Shepjepp
I doubt it since I haven't even seen one in 35 years and I'm old and hardly remember what I had for dinner yesterday...
Nvm great news I dint know the power switch was under the computer! I was taking it apart to see what was wrong and while I was unscrewing from the bottom I saw a switch, flipped it and it turned on xD some of the keys don't work though any ideas?
Shepjepp
is there a pattern to the ones that don't work or is it random... If it's a pattern like E,F,B,Y,J, in diaginal rows it means that a line to the mother board or on the Key Board is not passing the data.. This could be due to the Key Board connector having a bad contact... If its random like R, K and X don't work then it's proly corrosion on the individual key switch... Under each key on the Key Board there is a little metal cap that is flexed down making contact.. if corroded contacts under these little caps you don't get contact... I remember that you can disassemble the board and using a exacto knife lift the metal cap and clean the bottom of the cap and the two copper traces on the board where the cap makes contact and then you will have to set the cap back just right in the exact same spot and seal it down around the edges...
I spent a good portion of my childhood hacking on one of these. A couple of relevant points:
The machine ran at 1.77 MHz out of the box, but almost everyone who actually owned one and was at all into electronics ended up doing a fairly simple hack to double the clock speed, so an awful lot of these actually ran at about 3.56 MHz instead. That was actually _much_ faster and more capable than most of the competition at the time, which I think was part of why they were so popular. There was also a very common (I think almost ubiquitous) hack to add an extra RAM chip necessary to do lowercase (the character generator actually included lowercase characters already, though some of the earlier ones looked really ugly (they didn't do descenders properly), so that was often replaced as well). Radio Shack even offered a DIY "lowercase mod kit", if I remember correctly.
I'm pretty sure that the monitor was actually sold with the computer as a set, not separately. I've certainly never encountered any TRS-80 model 1 that wasn't bought with both the keyboard and monitor together. It was true that you could technically hook it up to any composite NTSC display (so you could display it on a TV if you really wanted to) but that required hacking up a custom cable that as far as I know Radio Shack never sold.
The tape deck may have been sold separately (I don't remember), but it actually worked with any common audiocassette player (it wasn't a special computer accessory or anything), which lots of people already had, and if you didn't they didn't actually cost that much.
The expansion interface (which was a box which sat under the monitor) didn't actually contain the disk drives. It just contained a drive _controller,_ which could then be plugged into external disk drives (which sat in their own separate box(es)) via a ribbon cable. (It also contained more RAM, printer and serial ports, and a few other extra bits, as I remember). You could actually connect up up to four external disk drives by daisy-chaining them.
The "Trash-80" name was originally coined by Apple fans, I believe, but a lot of folks in the TRS-80 community sorta turned it around on them, adopted it, and made it their own, and it became something of a moniker of pride in some groups.
The 64x16 character display was not driven by price (as far as I know). It was because that made the video memory space a nice round 1K in size, which was architecturally convenient for several reasons. It also made the character aspect ratio much closer to printed text, which made text applications nicer. Also, keep in mind that the 64 character display was at a time when other computers really only had 40 characters across, so the TRS-80 was actually much more capable for text applications like word processing than its competitors (which was the other part of why it was so popular, I think). The 64x16 screen was _not a compromise,_ it was actually arguably a much better character arrangement than what most other home computers had at the time this was released.
Regarding audio, you could, at the time, actually buy a little external speaker box which you could plug into the cassette port which the computer could use to play sounds. It only offered simple bit-banged (on-off) audio output controlled by writing 0 or 1 to a port, no fancy synthesized audio or anything, but there were actually some programs at the time that still made surprising use of this through PWM techniques, etc. There were lots of games and such that did include full audio effects using this method, and even a "music composition" program that featured multiple voices, and an editable graphical depiction of a musical score sheet, etc. These computers were certainly not "mute" by any stretch of the imagination.
It's also not really fair to say it had "no graphics to speak of". There were actually a _lot_ of games, paint programs, etc for the TRS-80 that made use of its pixel-graphics capabilities. Sure, it was only black-and-white, and you could only draw in blocky, non-square pixels, but you could still do a surprising amount with that if you put your mind to it, and many people actually did to good effect.
Oh, and it wouldn't actually hurt anything if you plugged the wrong cable into the wrong port, it just wouldn't actually work (obviously). They were at least bright enough to take that into account with the design.
Super fun hacker computer for back in the day... you could get books on how to hack it... including a full disassembly of the L2 Basic. I took mine and put 48KRAM, L2 Basic (used 64K EEPROMs in the original sockets, no extender board needed). It's very simple to add lower-case characters, they're in the generator, you only have to add one wire IIRC. My first real tech job happened because I was a Model1 hacker... all their industrial computers were based on it, Z80 stuff. Made things that connected to the parallel interface... EEPROM burner, etc. Still have that thing somewhere in my junk... you haven't lived until you've used cassette assembler (EDTASM).
@Scowell - I did the lower case hack to mine as well (using wire wrap wire, which was pretty common at the time). You just had to cut one trace from the character generator ROM and run it to the one RAM chip - (data bit 6, I believe) - which wasn't hooked to the CG ROM originally. I remember being thrilled to have lower case, but disappointed that the CG didn't have true descenters (so lower case G's, J's, P's, Q's, and Y's always looked funny, as they sat slightly above where they ought to have been in the line of text).
Wow the new desk for tear downs is absolutely perfect--looks great!
Yeah, I'm liking it a lot, it's going to get a lot of use for all sorts of stuff. The goal is to keep it entirely clean!
EEVblog
good luck :)
I used a Trash 80 while in the Navy with scriptset as the word processing program to write Nuclear Plant repair procedures.
"Mem Size" was an input where you could reserve memory at the top of address space by lowering the space the ROM owned. Then you could stuff your reserved space with whatever you wanted, including machine code routines.
on SDLTRS it asks for the memory size but any number must be in the thousands.
for CASS IDK
I still have my Trs 80 model 1 level 2 in a box somewhere. It was my first computer. Bought it in 1980, a big 16k ! Really enjoyed basic programming on it. They had magazines with games you had to type in which I did and always had a mistake when I ran it.. I had to recheck the 100s lines of coding... argh! but it was fun.
Sadly I don't know what I did with mine. Would enter programs from 80 Micro and other computer magazines.
One of my first computers, handed down from my Dad. We had a hardware hack that put in some extra logic and a toggle switch to toggle capital/lower case letters for use with the Electric Pencil Word processor... And I actually used it up until High School for Word processing..
Also had the Level II basic expansion.
Nice!
The "Level 2 BASIC upgrade also added the bigger character set ROM to get you lower case characters. Oh, and I believe that the two asterisks, with the right one blinking to show you progress while a program was loading from cassette? That moved from the top left to the top right with the upgrade.
I think the upgrade was $99 and you had to send it to Radio Shack (and they sent it away to be upgraded).
I installed 16K of RAM myself. It was 8 individual chips in a blister pack all pressed into an anti-static pad. Also cost me $99. Crazy.
In the US market, for $599 you had a complete bundle (and large box) with the 4K computer, the modified RCA 12" set, the power supply brick and the cassette recorder. It's so hard to imagine that the joke of a company Radio Shack is now would have had such a product! Ditto for their audio product line, which in the US was quite good actually. I worked there back then, and that was an era when you weren't ashamed to admit it.
Love it, the Tandy catalogue was the thing of dreams when I was a kid, and I'd have loved a TRS-80, but they were too pricey. Of course, the home microcomputer boom solved the price problem thanks to the Z80 processor, and Sir Clive Sinclair, and Acorn Computers using the 6502. Happy days, writing BASIC programs, and waiting 20minutes for a game to load from cassette on my Acorn Electron.
My first job was selling computers for Woolworths as a Saturday lad, 32 years later I still work in IT. These machines shaped the modern world, and our lives.
Oh man!
This is the one that started it for so many folks...including me!
THANKS DAVE!!
A loverly trip down memory lane dave. I remember my friend asking me to drop by his place to check out his new personal computer back in 77, that is where i started programming computers in BASIC and later bought an Energy Control Apple ][ + clone.
That extra key near the EI connector is a reset button. They used to have a cover which would flip down and protect the connector. Most people discarded these as they got in the way of the reset button. Also, the monitors did come with a grommet. :-)
I used to be a software dev at Microsoft, and I personally saw and heard BillG say that the Model 100 had his last _significant_ amounts of new shipping code. He said it during the Q&A section of a company meeting, circa... 1994 or something like that. Not necessarily the _very_ last code he shipped, but the last meaningful amount of new code.
The MEMORY SIZE? was indeed shortened in later versions to MEM SIZE?, the rest of the initial message was also shortened to R/S L2 BASIC to create more space for the revised ROM.
If you press Enter, you got all of the available RAM for BASIC programs. Entering a number there reserved some of the memory for use with machine code instead, reducing the available memory for BASIC programs.
The other switch on the back was fitted as standard and is a hardware reset. Not of much use in the base unit other than to recover if a load from cassette failed, but it had various uses if the expansion interface was connected.
There should be a plastic cover over that switch and the edge connector, made of the same plastic as the rest of the case.
All spot on. I lost the plastic cover many years ago as I always had either an expansion unit or (later) a printer interface plugged in. The reset was useful if any external IO device locked up including tape, printer, serial, fdd, or anything on the bus.
I recall mine saying "MS L2 BASIC", some years passing before I realized it had been MicroSoft. Purchased mine in 1980 so it must have been one of the latter ones.
OMG, I remember it like it was yesterday. I paid like 3 months worth of rent and bought a Trash 80 back in 1979 when I was only 19 and wasn't sure what I wanted to do with my life.
I drove back home like a mad man, with my first computer on board. Got home, and the first thing I did, was what normal people don't do.
I opened it up to see what's inside. Was fascinated by it, and how tidy and beautiful it looked inside.
Spent about a day and wrote my first program. An analog clock. Jump with joy when it worked at 6:00 am the next day.
This shit of a computer, decided my fate. I enrolled in the EE program at North Texas university and it's history from there.
From that date on, I bought every computer that ever came out (including the TR-100). That was until I started building my own custom computers with PC clones and I've never bought another off-the-shelf computer.
Thanks for the nostalgic recall :)
Man... Talk about a trip down memory lane. I remember playing on these at Radio Shack. It's the machine that I started to learn to program on.
I love these teardowns. I recently moved and found my first PC stuffed in a crate that I had forgotten about. It was so much fun opening it up and powering it up again. It was HUGE! Six inches tall, 24 inches wide and 18 deep. It had the very first generation Intel 386. And it was the first PC that came with 1 meg of RAM. It operates at 20Mhz and has a 20 meg harddrive. And, it had two 5 1/4" floppy drives! DOS 5.0 The hard drive was corrupt so it would not boot, but I cannot bring myself to get rid of it.
Great to see this computer again. Brings back some great memories. Thanks.
The Model One was my first computer. I bought the floppy drive expansion box and the original Radio Shack branded Centronix dot matrix printer. Learned how to program in Basic on the Model One. Upgraded to the Model Three as soon as I could. After the Model Three came the Apple Mac-Plus and I am still a Mac user.
I spent many an hour programming in BASIC on my TRS-80. I loved it. Thanks for the memories !
I had one - received as a Christmas gift from my dad in 1977. It was great.
We had a TRS-80 Colour Computer 3! So excited for this!!!
We actually owned a Video Genie II with the numeric keypad (TRS-80 clone).
Upgraded with 2 floppy drives, 300 baud modem and graphical upgrade.
We completely took it apart and mounted it in a desktop case with separate keyboard case.
Best computer years I ever had!
Notice the holes in the front of the monitor case for the channel selector knobs? They are covered up by the gigantic label.
It really was a retrofitted B/W TV!
My grandfather gave me a TRS-80 CoCo2 as a kid, I just hooked it up to our TV and bought a cheap tape deck for saving data. Worked great.
I still have mine. Still works.
This video was a trip down memory lane for me as this was my first real computer after building a single board MK14. I wrote and sold some programs to run on it and spent many happy hours in the local Tandy shop on Saturday mornings swapping ideas and programs.
Unlike mine though the "silver" coating on the front of the keyboard seems not to have worn away.
Happy days
my first computer as well... mine was the level one with the ROM upgrade board that converted it to a level 2, and added the keypad, after you cut a hole for it!! BTW, the little switch next to the expansion port was a hard reset, that you needed sometime when doing asm programing!
I made clone of that model I with my friends as a hobby project in beginning of -80's, pcb and everything. It worked when we figured out that due different TTL's it tried to boot to disk unit proms, but when some resistors where added to extension bus it booted without it. I still have it, it is not exactly same because keyboard was different, but 99% same. Keyboard was made from old IBM machine (white and blue keys... :) and monitor was tv with video input :) . We where kind of professionals at that time working with 8080 based boards, so we know what was going on.
Very cool project at that time :)
A 16K Level II BASIC TRS-80 Model 1 was my first computer, back when I was 12. I used the snot out of it. Things I remember:
- The keyboard felt good, but had an awful keybounce problem (i.e. repeated letters). There were a *lot* of third-party debounce programs you could get and it was pretty much a requirement to load one every time you started it up.
- I remember taking the trim panel off the monitor and seeing the holes where the tuner knobs would have been in its original design as a TV.
- I played most of the Scott Adams (different guy from the one who draws Dilbert) Adventure games - lots of fun.
- There was a third-party peripheral called the Orchestra-80 which you could hook up to the slot where the expansion interface would connect to and which would allow you to play 4-voice music.
- My favorite game was SubLogic's Flight Simulator 1. 3 frames per second at 128x48 resolution, but still, I was flying!
- Assembly language programming went like this: 1) Load the assembler (from tape). 2) Load the source code (from tape). 3) Edit the source code. 4) Save the source code (to tape). 5) Assemble the code (to tape). 6) Load the assembled code and run it. 7) If there's a bug, return to step 1).
We used Model 3s and 4s when I was in school We had someone demonstrate the coolest thing I ever saw one of these do. Actually that should be heard, not saw. The screen didn't do anything. He placed an AM radio next to the computer and tuned to a free frequency. The program he loaded started playing a digital noise version of Michelle by the Beatles!
The first computer I ever used. Our 7th grade computer lab in 1978 had about 30 of these PCs. I vaguely recall the storage device on a cassette tape player and the computer seemed very, very slow. Ah, the memories...
It only started being refereed to as the "Model I" when they made the Model II. Technically, it was just called TRS-80 Micro Computer System..
yup. just like world wars. :]
I was a Commodore 64/128 user. I remember those Radio Shack computers.
Dave, Jumper detected: North of R48 on right hand side of the board(3~cm to the top-left of the Z80).
Also, no mention of the brand of the caps being Nichicon?, still working after 37 years, that's what you get with a top brand!
No, don't ruin it for me!
EEVblog come on, surely you can forgive ONE very little jumper on what looks to be a cap footprint! :D (maybe an RC filter in which they removed the cap?).
(BTW, i like the new bench, gives much more room, how long until it's filled with random stuff? :D)
Guillermo Lovato
In that case, ok, I can live with that.
The goal is to keep the new bench completely crap-free!
The caps are still good because of low "on time". My guess is this particular unit was not used or rather powered up for long periods of time. I pull these things (Nichicon) out of gear all day.
Joel Gette Nope. Was used at home and work for 6-7 years then spent 3 years driving a series of printers to print manufacturing labels. Fastest way to get it ready to load a new program was to flick it off and on.
good that he noticed the different size screws. The spacers are equally important. Radio Shack repair shop once sent one back to me with all the spacers missing and wrong length screws in some of the holes.
Sending me down memory lane here! Although for me it was the TRS-80 Color version that a friend lent me during the 80s, back when I tinkered with BASIC programming, some of it coming from Compute! magazine....
ohhhh ... My first computer :))
Mine had dual 5.25" floppies. Probally the model II.
In college they dumped a big pile of junk and in there I found a TRS-80 monitor. The model number is KTR 122S, manufactured in December 1977. It has a gromet in the video lead, and the chassis is different. I don't know why the flyback lead has no insulation cup, there was some corona discharge producing ozone in mine, so I installed one from an old TV.
It appears it feeds on a composite signal isolated by an optocoupler.
I used one of these in high school in 1979. The "monitor" is actually an RCA b&w TV. I had one at home in the mid 70s.
I remember learning BASIC on a machine very similar to this one. Wow, brings back memories.
I've really gotten into retrocomputing over the last year, so I especially enjoyed this teardown. Thanks, Dave!
Awesome! My first computer that I got in 1988 was a Commador 64. I was 8. It was bought in a garage sale. But I did learn a lot from it.
I used to program at school with an Apple II Europlus, but since I could not afford one of these at home I used to play around with one of these in the local Tandy store. Probably with the TRS-80 Model III or IV. In 1982 I bought a TRS-80 Color Computer and loved to program on this for many years. It's in my garage somewhere and I want to pull it out someday :-)
Nice video. I thought you might give a shout out to the Dick Smith Electronics compatible computer that was also sold in Australia.
The expansion module didn't have a floppy drive within it. Instead it allowed multiple devices - printer and floppy drives - to be connected. The box was bigger than the computer but most of the space to allow the external power supplies for the computer and the drive to be included within it. The problem in Australia was the 240V supplies were too big to fit.
My brother and I grew up playing the various games on one of these, so much so that we wore through to the second layer of plastic of the case just under the keypad. (Our father used VisiCalc and word processing). Sold mine at a flea market for next to nothing. I hope the buyer got value from it.
Ours also had a third party patch which allowed hanging characters in the word processor. I still remember going with my dad, back to the computer store opposite Nunawading Station in Melbourne, to get it installed.
A very fine looking specimen of a classic computer, if ever I saw one.
Your tear downs are so insightful and packed full of knowledge!! Very interesting stuff!! Please keep up the great work!!??
10:37 - TANDY! Was the best store in the world. Used to love going in there and sniffing the packs of 1/4W carbon resistors. Mmmm, electronics smell!
I learned to program BASIC on one of these. :-)
I had one of these in 1978!! I learned all about BASIC language, and used it a lot and had a lot of fun doing it!! --- John A Bellas I think my unit had the 16 K upgrade and tape drive (CASSETTE) .
I had the original model (have) that I bought when I was a paperboy! Speaking of loud RF coming from it, there was a music program for it that used the effect very well. You had to tune a radio to a certain frequency and set it next to the computer to hear the music! The song that came preloaded in the program was the flight of the bumblebees! Ah, those were the days!
Have one in my attic, along with a few Model IIIs. Had some of those RCA TVs in the family too. A 19" in my parent's living room and the 12" in my grandparents kitchen. The rotary tuners were in the area covered by the label panel on the Model I monitor. The volume control in the hole the cable is coming through.
TRS-80 Model I, my Father's first computer when he was a littler younger than I.
The Expansion Interface didn't have room for floppy drives. it was a plastic platform that had room for a single largish PCB and a cubby for a daughter card (extra $$) if you wanted an RS-232 interface. There were cut-outs around the periphery to expose connector edges on that PCB or various things, including a port you could use for external floppy drives. Originally single-sided, 83K floppies.
To save money, we used to use a paper punch to cut out a symmetric notch so we could flip them over and write on both sides. :)
I never had a look into the TRS80. Thank you for this insight, Dave!
Layout of PCB has certainly come a long way since that was built, can remember using black tape to make traces for a PCB shop in the 80's then shortly getting to use a Computer Vision that took up a whole room. I have respect for the person that layed that board out by hand back in the day.
redlored100 Indeed. Was quite a skill to lay out boards back in the day. I remember ripping up tape!
At the beginning, I zoned out, and thought I was watching the antiques roadshow. Dave is just so great at these things :D
Picked one up a while back on Craigslist. Love it. Found cassette files in mp3 format online. Really cool way to load up programs. Takes forever though.
I had the Hong Kong rip off of the TRS80 called the Video Genie II and loved it. It even had a build in tape deck with volume control. 16K memory and learned how to program in Assembler. Those were the days. :-)
I have a video genie but case has been damaged badly in posting and seems to have had a mod on the pcb, not yet got it working.. :-(
built in cassette deck.. pretty swanky
I'm in my early 50s... in eighth grade my school got one of these. And we did the print name thing. And some programs. I remember seeing it in the RS catalog before that just dreaming about having a computer.... a COMPUTER in my house! I knew computers back then as something in sci fi / adventure shows. The TRS 80 would've ben like having a spaceship in a real way.
Thanks for the memories!
CJ, Let's go back to 1977 for a moment. Disco playing on th eradio......uh, maybe not Fleetwood Mac....better. OK.
Now we're back in good ol' 1977. You said "a COMPUTER in my house!" In 1977, could you have imagined carrying a friggin computer in your pocket???????
Great retro teardown! Lots of fun to watch! Nice job.
This was the last computer I owned where I knew the entire schematic almost by heart and understood exactly what every gate did.
In that classic ceramic package, I love it.. They are vintage stuff. :D
Very cool, that monitor was so built to a price point, and dead simple to make. It started life as an RCA as Dave mentioned, To make it into a monitor, tuner and IF section was removed the IF, video/audio demodulator was all on that circuit card standing up in the left of the TV it was then replaced with a direct video drive board and the cable run out the place where the volume control had been and a plate placed over the holes where the tuner had been. Made in Taiwan
The higher end RCA TV's of the era like the XL-100 color sets where made in Indianapolis Indiana.
OMG. I remember this well. Here is where I started. TRS-80 rocks.
I started school in September 1980, and TRS-80 Model IIIs with dual 5¼" floppy drives were the only computers there. I don't remember if they were there in 1980 or not, but they were there at least by the time I was in second grade. The only thing we ever used them for was playing a math game. It would present you with an arithmetic problem and you would type in the answer and hit enter. After a certain amount of problems, it would show your time of completion and percentage of correct answers. I wonder if that was a commercial program or a homebrew.
Sound was achieved through the cassette out connected to a small telephone amp (or whatever amp you wanted). All the games supported sound that way. The button you were pressing by the edge card connector (tucked in back) is the reset key, soft to push, hard if you hold down break while pushing it. Also, the monitor did have a grommet or some sort of strain relieve there, it was missing on that model, but google pictures and you'll clearly see it. I did a lower case mod on mine that involved soldering a ram chip onto another (piggyback), that and a replacement char gen chip, hence the reason it was socketed. I worked at radio shack and I asked the tech about getting it done and said save yourself the money, tossed me a chip, a piece of wire and the char gen and I did it myself. Also, the expansion unit didn't hold drives, it enabled drives, (contained the drive controller hardware), as well as an additional 32k of ram, an rs-232 board for data, a printer port, and a data bus since you use the one on the main cpu to connect to the expansion interface. Interesting thing about all the RF you covered. A guy (from my home town actually) wrote a program that would play music, wirelessly of course, from the computer to a nearby radio. He used machine language loops and figured out what sized loops produced what frequency and had the computer playing music through radios :)
nice. I learned how to type and program basic on those old beasts. Still so weird to think back about saving to cassette
I learned quit a lot about computers from my TRS-80 Model I, which includes writing programs in BASIC and Z-80 assembly language. The Level II BASIC was enhanced version of Microsoft BASIC for the Z80. Of all the early PCs, it was unique for having 16 lines of 64 characters as well. Several companies made clones of this as well ...
you tearing down those machines is perfect material for binging RUclips, keep up the good work!
Back in the 70's and early 80's when I worked on developing solder mask technology, getting the coating to work over tin/lead was a pig, 3 cheers for the transition to SMOBC and HASL technology.
This was my first computer when I was in high school. My grandma was going to get me a car but I wanted a computer instead. It was really like futuristic magic to be able to type in a program and have it work. I ended up having 2 or 3 later TRS-80 computers after it, but finally switched to Apple when the Mac came out.
I make it from scratch when I was à young man. In the 80'. I have a lot of pleasure with my clone of trs80, with floppy disk 8''. Now, I'm retired and have fun with arduino and raspberry. But I buy it, no make with my solder Iron, and this it's no very fun. René from France.
The level 2 rom kit is the add-on board kit located in the lower front corner of the keyboard/main unit as seen with the top cover off.
The Model 1 was my first computer. A very expensive Xmas gift for a13yo. I had 4 siblings and we were not a well off family. I think my parent saw it as an investment. After I got it I don't think I slept for three days. You couldn't do anything but program it and that is what I did -- and still do today. I added the expansion interface, a printer and two floppy drives over a few years which gave me a whopping 16k of ram. I sold it to a comp sci professor at a local college and then bought my next PC. I considered an Apple 2 but ended up with a DEC Pro 350. Maybe I missed a bet there but knowing more server side stuff has serve me pretty well.
Nice video!
I had one. Bought it with 4K RAM but Radio Shack allowed me to upgrade it to 16 K RAM without warranty issues.
Later I added another 2 rows of 16 K RAM piggybacked on top of the original ram with the Chip Select pin driven by an extra decoder.
I replaced the character generator with an EPROM and added some memory for lower case.
In the end, I could switch it between the normal character set and one with the special APL symbols.
And, of course, added better graphics.
I got hold of two 5 1/4 inch floppy drives and designed and build the disk interface and a real-time clock and serial port to connect to a home build 75/1200 baud modem to get on the bulletin boards.
The PCB edge connector for the expansion interface was absolute rubbish. I soldered a proper gold plated connector onto it.
I never had so much fun later on...
There was a 68000 expansion board for model II for running a xenix operating system.
The system become a dual CPU, Z80 for I/O handling and 68000, with her own RAM, for the unix OS, FANTASTIC !!
I still have my grandpa's C64, like new. Was kept in a basement under it's cover for 30 years.
If I remember well, the keyboard scanning was implemented by having some CPU address lines being shorted to some I/O port lines by the keys, so the keyboard took something like 4K of "address space", hence the 48K RAM limit...
Have the service manual to this some where !
The stick on the LOPT to the tube is a diode
Repaired a few in my time.
Nice bit of nostalgia thanks.
I use to be writing codes (Basic & Assembly) on this machine during my younger days!! This beauty is good. Very responsive.
EEVblog Re the speed of the Trash 80 vs the 6052 based machines, the Z80 has a horribly inefficient bus system compared to the 6502*, resulting in very roughly half the MIPS for the same raw clock speed. At the time, the default clock speed for a 6502 was 1MHz, & that of the Z80, 2MHz, for comparable performance levels, modulo cycle-stealing for DRAM refresh & video controller access, etc.
* Plus the 6502 had hard-wired instructions, vs microcode for the Z80, which gave the Z80 fancier instructions, but required more cycles.
Yep, the 6502 had a multi-phase clock too, which allowed it to do more with each clock cycle. It effectively operated at double the headline clock speed. It's efficiency directly inspired the ARM's architecture.
Electron Alchemy WOW! I didn't know that and I'm a commodore Whore. Thanks ! 8)
Electron Alchemy Yes, that's what I was meaning about bus efficiency.
Common misconception, but the Z80 instructions WERE hard-wired. Even back in the day (1978 when I was working for Tandy selling these things as a teen) there were people running around saying "microcode, microcode". They were wrong then, as now. In fact, the history of Zilog (and the Intel defectors that started it and completely decimated the 8080 with the brilliance of the Z80) is fascinating on its own.
Once you learned some assembly these things FLEW. It was easily possible to get 60 or more complete screen refreshes per second... if only there was enough memory to store that many interesting frames. And of course the hash on the screen from refreshes while updating... it was "new tech" to even consider waiting for the scan retrace to start writing.
The fun comes when you realize that the Z80 had a 4 bit ALU. www.righto.com/2013/09/the-z-80-has-4-bit-alu-heres-how-it.html
Very entertaining video, I remember playing with the TRS80 when I was a kid. My first computer was an Atari 800 home computer. The Atari 800 probably was the first really affordable do it all computer. I remember I had a thick book of nothing but basic programs that I typed in by hand and then executed. Those were the days, my iPhone and iPad are far more powerful and entertaining then that was but I remember spending days and days at my Atari 800 computer. Thanks for the video.
Many kids from the 70s remember the Apple II and Commodore PET because of their popularity in schools. Even if the TRS-80 outsold both in actual units, the vast majority of people didn't have any computer at home, School was the first place most of us touched a computer. (in my case it was the Apple II) I was very aware of the TRS-80 as I was a budding nerd whose yearly rite was getting the annual RadioShack catalog. I'd end up with a I and later a III. The one Radio Shack computer that Gen Xers have a fond memory of is the TRS80 Color Computer, An entirely different machine.
That is the upgraded Alps keyboard. The original had Hytek keys. That "hidden" button is the reset button. The "expansion thing" is the Level II basic ROM set.
I had a 16k Level II when I was working in the computer industry. Used mainframes by day and the TRS-80 by night. Zork and Interdictor Pilot were my favourite games. This was in the UK btw. I have no clue where it ended up sadly. Same with my Commodore 64, 64-C (yeah two very different models of the same computer) and various bits of hardware.
Here's the model 102 teardown video Dave mentions in the video. EEVblog #116 - Retro Notebook Teardown - Tandy TRS-80 Model 100