TRS-80 Resurrection Part 2: Tackling the CRT and floppy controller circuits
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- čas přidán 12. 03. 2023
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Part 1: • Trash to Treasure? I r...
De-soldering alloy: amzn.to/3UcWwuD
Continuing the resurrection of the #1 RadioShack TRS-80 Model III system. Tackling the CRT and floppy circuits
As someone (cough) of a certain age who lived in the era when all of these systems I see on your channel were actually "current hardware", I'm glad to see someone in your generation who finds them interesting and cares to learn about them. Glad I stumbled across your channel!
It's quite refreshing to witness some "old school" troubleshooting at the component level.
your channel and narration is so peaceful its great for me to drift off to sleep to with techie dreams
Very careful and meticulous, and a soothing voice to drift off to if your sleepy. I am almost 46 so I have lived through all of the computers presented here on this guys channel.
I was born in '85 and started working on PCs in the mid-to-late 90s. My brother used to talk about the pain of working on TRS-80, and a few other 80's PCs. The lack of standardization even within "the same" models really stands out here as a reminder of why things like ATX are so important today. Thanks for making these videos - it's cured me of any future curiosity to dive into working on these! 🤣
Thanks! This is the deepest I’ve been into 8-bit hardware. Coming from an x86 background, it’s been quite an adventure!
@@miketech1024For sure it's a whole other level of skillset needed to really understand these things at a deeper level. Your board-level repairs in some of these videos are pretty damn impressive man - it's a skillset I wish I had developed more growing up. Thanks for taking the time to shoot and produce all this - I know what a pain it can be to setup a camera just right or perform otherwise simple tasks with one hand, etc.
Out of curiosity what were some of your influences/mentors as a kid growing up? Do you come from a tinkerer kind of family? I had my older brother who did vo-tech for Solid State Electronics so I learned almost everything from him starting out. I think you could probably talk about this stuff more in videos and people would find it compelling. Most of us tech nerds really seem to appreciate the lineage of "how we came up" as time goes on, and I think you could probably incorporate a little story time into demo'ing some of these systems.
Thanks for saving these old guys. The trs-80 1 was the machine I cut my teeth on, and I still have a real affection for them.
Randomly was recommended your channel and I am here to stay! Really enjoy the content, keep it up!
Thanks so much!!
I like these kind of series. I hope you continue it, I am curious to see if any of them can be fully restored.
Your floppy controller situation is like how my family always seemed to end up with things that were rare. Rare tube radio. Rare turntable. Rare Ford station wagon. All difficult to find manuals of.
Not sure if this has been answered yet, I scrolled down but didn't really see anything.
Ok, ONE: The RPM of all low density 5.25" floppy disk drives is 300 RPMs. High density 1.2mb drives are the only ones that spins at 360. So yeah, change that back to 300RPMs.
Two: Your drive select is wrong. If the motor spins, but the light does not come on, it's usually a drive select issue. You may need to change the drive select jumper near the back of the drive. The first drive should be selected as drive 0 and the second as drive 1.
Three: The last drive on the cable must have the terminator resister IC installed, If you're using a single drive, then that drive must have the terminator on it. If you have two drives, then the last drive on the cable gets the terminator IC.
On some TRS-80's the cable is keyed so that Drive O will only work in the drive O position. So keep that in mind. You can replace the cable with a straight through cable, but then you will need to set the drive select for each drive appropriately.
You can use double sided 360k drives in place of the single sided drives. You can also use 3.5" drives but only if you can set the drive select jumper number from 1 to 0 to make it a boot drive. Most newer 3.5" drives don't make it easy to change the drive select jumper.
Hope this helps and I didn't just confuse you more. Good Luck!
Looking back through your video, neither one of your drives have a terminator IC installed. I wonder if someone took it. Or there's some other kind of termination going on in your systems. I'd check the other TRS-80's drives and see if they have one.
So nice to see you giving a TRS-80 some TLC! The first computer we had was a TRS-80 model 1. Using that, starting at 5 years old, sealed my fate as an IT nerd.
Ooh! TRS-80! My first computer was a Model III. I got as a gift when I was in junior high.
Mine had 2 360kB floppies and 48kB RAM. I first learned how to program on my Model III.
I used both TRS-DOS and L-DOS on it. I preferred L-DOS. I once used a Z-80 assembly routine to produce sound via the cassette port. Turned out that was a common technique for sound in commercial games.
That computer was loads of fun. More fun than my PCjr!
Nice! These are actually my first TRS-80s. I’m pretty new to the platform, which has kind of hindered my efforts to get them working. However, I refuse to give up because I really, really want to play with them!
@@miketech1024 Adrian Black may have some pointers on his videos. He has some videos on the Model III.
The RIFA caps used on many 8-bit computers’ power supplies are notorious for failing (sometimes very spectacularly!). They are ticking time bombs.
I don’t recall having power supply issues on my Model III.
I do recall the cassette port being finicky. Then again, thankfully I never had to use it for saving/loading software.
I think on a few TRS-80s, you have to press and hold Break while hitting reset to bypass the disk drive to get into cassette basic. I don’t remember that being the case with my system.
@@DerekWitt Oh yeah I absolutely love Adrian’s channel! I used the diagnostic ROM he co-authored to debug the DRAM communication issues. That got me from a garbled screen to the Cass prompt. Unfortunately, I can’t seem to get the system to realize that it has a floppy controller. The controller card that’s in there is different than the one specified in the service manual, which another viewer mentioned might be due to it being from an aftermarket upgrade kit. This machine has certainly been a puzzle…
@@miketech1024 Hmm... that is puzzling indeed. Yeah, it being a third-party kit is certainly possible. Radio Shack was quite good with their service manuals. If your controller card has a part number etched on the PCB, it could be a Radio Shack one. Who knows!
I ran into your channel just today. Great content thus far. :)
Really enjoy your vids. Thanks!
Loving your channel, Mike! I got to ask, how did you become so incredibly knowledgeable about all this stuff?!? It's amazing and it's been so fun to learn from you in these videos. You're channel is going to explode, I know it!! Keep up the amazing work!!
Thank you so much! It’s just been my labor of love for a very long time. I’ve been interested in all things tech since early childhood, starting when I was about 5 years old. It was the Apple II in kindergarten that captivated my imagination. Then I started watching a show called The Computer Chronicles where they’d often discuss technical details of systems. I just soaked it up like a sponge. My dad was a radioman in the Navy and a highly skilled electronics engineer. He was also getting into computers around the time I became aware of them, so I learned a LOT from watching him. Feels like tech is in my DNA. Then I discovered the world of open source (thanks to Linux) at around 12 years old and my future was made. Today I work as a Senior Systems Engineer (specifically in DevOps and cloud infrastructure) for an amazing Fortune 500 company. Feels like what I was born to do. 🙂
@@miketech1024
Any advice for someone just about to launch their career? I graduate next year, I want to work in firmware, or something related to embedded systems. I tried to build up a portfolio of projects to show off, but I'm still afraid it won't be enough.
One thing that annoys me about myself, I'm really good at understanding how things work on paper, but when it comes to practical design I'm a failure lol I want to overcome that feeling.
Anyway, love your content, been nice discovering your channel.
@@dtraindaimyo3377 Thanks so much! It’s hard for me to say since I kinda took a non-traditional path. I went straight to a sysadmin role using all the stuff I learned growing up, then into network engineering and cybersecurity, then finally to DevOps/cloud (with a few years as an IT manager in between, which was gross). Let me tell you, imposter syndrome is REAL lol. All of the best people I’ve worked with, interviewed and hired have it! I don’t have much professional experience with embedded systems, but do tinker with them here and there. You’ll definitely want to get familiar with Linux as more and more embedded systems are using it over a proprietary RTOS. Check out RTLinux, it uses a real-time kernel. There are of course more traditional ones like RIOT-OS which are free and open-source, but I have never worked with it. If you haven’t already, you should build a home lab as it will be your most powerful learning tool. Being able to build and test things in the comfort of your own home and without fear of consequence goes a LONG way. That will absolutely help you to build your practical design skills. I once made a very brief (and I mean VERY brief) inquiry into what it takes build an embedded systems lab. You probably already know about it, but there’s a lot of cool stuff and great info at www.embedded-lab.com
Though I don’t have intimate knowledge of the specific job market your targeting, tech workers in general are in really short supply (my LinkedIn inbox agrees). As long as you have some demonstrable skill, I have no doubt you’ll make it. Once you’re in, your skills will improve exponentially as you learn the most by doing, and gain access to the experience of your co-workers. Don’t worry yourself about not knowing everything up front, literally nobody does and any decent manager is fully aware of this. The best new engineers are those who know what they do not know, and always have their eyes on the docs. This remains true for senior-level engineers as well. There is no shame in googling! In fact, I encouraged the people on my teams to do so. I hope this helps a little bit.
Thank you for this interesting video, I really enjoyed the repair of the CRT part!
Just a quick remark on the choke in the second disk drive: I assume it is in some kind of filter circuit, probably in line with one of the supply voltages and something behind it is shorted, causing over current and smoke ^^
Keep up your excellent work!
Thanks! Fortunately that disk drive’s schematic is covered in the service manual so I’m optimistic about its resurrection. The other drive seems to be a later revision with a slightly different circuit (probably explains the cheapened latch assembly).
Looking forward to part 3
Your videos are cool, i love retro computers, subbed :)
I've used vaseline on CDRW rails and it does a great job.
These videos are amazing. Keep them coming!
Thank You for this video!
love the channel bro
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G'day Mike, from memory SD & DD drives run at 300 rpm and only High Density drives run at 360 rpm. Your FDC doesn't match anything in my service manuals so maybe an aftermarket brd. Possibly an upgrade from a cassette only computer to floppy.
Oh wow so the spindle RPM was indeed set correctly! The FDC being from an upgrade kit does make a lot of sense, seeing as the drive revisions are mis-matched. Do you know of any telltale signs that would indicate if this machine was a cassette-only system originally? Thanks for the info!
@@miketech1024 Hi Mike, I've tried numerous times to post links and info on these comps and the FDC but the AHs @ YT keep deleting my reply. Maybe your filter settings?
@@gazza8234 Hmm, not sure. Maybe you could use a URL shortener like bit.ly If all else fails, could you send it to my business inquiry email in the channel about page? I really appreciate it!
@@miketech1024 Gave up on YT so info sent to your email
Could you post basic programs that access the floppy as shown here?
I only ever knew one person who had one of these , i'm pretty sure it only had a tape loader not a floppy disk . I bet it got thrown out when they shifted .
Hi Mike, wondering if any custom PCBs might be required for any repairing work? If so, would love to supply some freely and reach any cooperation together if possible. (PCBWay zoey)
Thanks for reaching out! I certainly will be needing custom PCBs for many things. I’m thinking about designing a modern floppy controller for the TRS-80s, among other things. Could you send me your contact info? I can be reached via the business inquiry email address in the channel about page. Thanks again!
If one drive is not responding isn't it then that it is configured as the other drive?
Tried both drive addresses, but no success. What’s strange is I can toggle the spindle motor on either drive, but I can only trigger head movement on the 3.5” drive. Pretty sure there’s something basic I’m missing. Judging by how far out-of-spec the spindle RPM adjustment was, I think the floppy controller board is similarly out-of-whack.
@@miketech1024 Back then drives could have four addresses, if I am not mistaken. And if I remember correctly, some disk controllers would not like work with some diskdrives, are both drives from the same era? I think TRS-80 is very interesting, the designers did a lot of stings they shouldn't do, like incompatibility between "Model 1" and Model II etc.
@@vanhetgoor The model II was intended as a completely different system aimed at the business market.
Model 1, III and IV are all very compatible. While the model II, 12, 16 and 6000 were all pretty compatible with each other. The model 16 and 6000 were to a large extent modell II and 12 with a 68K card added (giving a dual processor. Z80 handling I/O and video and the 68K doing the heavy lifting)
@@Agnemons Tandy Radio Shack made a mistake by making a special computer aimed at the business market. If they would have made one expandable system they could have served both the consumers and the businessmen. One keyboard and one power supply would fit all computer users. Adding drive to the computer would make it capable of doing serious work but still being able to read and write to and from cassette would still make it possible to play games with it.
Now in 2023 the Z80 is still being produced and it is still being used in professional equipment, Tandy Radio Shack could still have been a part of the computer industry if the consumers would not have dropped TRS-80.
If you owned a TRS-80 and you wanted to do a little more work on it, you needed a complete new computer system, this made the consumer lose faith in the TRS-80, so the "business model" was in fact the end of Tandy.
well as a means to vent your frustrations take the boards and the drives out to the range an just shoot the living daylights out of them. or just step out your back door and throw them as far as you can. lol.....
I could never hurt an innocent floppy drive like that! 🤣
aww, even the most humble Model 3 deserves wuv.. ;)
This may have been caught in the next video but the faulty controller seems to be missing an IC, unless I am way off base.
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