Restoring A Vintage Computer And Its Plotter

September 22, 2025 by Bryan Cockfield 17 Comments

Repairing vintage computers is bread-and-butter for many of us around here. The machines themselves tend to be fairly fixable, assuming spare parts are available and there hasn’t been too much physical damage. Peripherals can be another matter, though. Since they interface with the real world they can have more esoteric problems that aren’t always solvable. [joekutz] was handed just such a device in the form of a CE-150 docking station for a Sharp PC1500 Pocket Computer, which has a plotter built in. Here’s his “tip” for getting plotters like these working again.

The first step here is to disassemble the original, dried out pens to scavenge a few of the parts. The outer case needs to be kept so that it can be put back into the plotter, and a small O-ring is saved as well. To replace the dried-out tips [joekutz] discards the original tips and replaces them with tips from a common ink pen, using shrink wrap tubing to help fit the pen’s tip into the original plotter cylinder. He also takes the ink from the pen to fill the plotter’s cartridge, completing the surgery on the multi-colored plotter and bringing it back to life.

Of course this build goes well beyond the plotter, including bringing the PC1500 back to life as well. There are a few other videos about this project covering that original restoration as well as demonstrating some of the quirks of how this computer is meant to be programmed. But we mostly focused on the plotter here since that is a little bit out of the ordinary, and we’re also sure that refilling ink cartridges of any sort gets under the skin of everyone at HP.

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Exploring The TRS-80’s Color BASIC’s Random Number Function

August 8, 2025 by Maya Posch 6 Comments

Although these days we get to tap into many sources of entropy to give a pretty good illusion of randomness, home computers back in the 1980s weren’t so lucky. Despite this, their random number generators were good enough for games and such, as demonstrated by the [CoCo Town] YouTube channel.

The CoCo is the nickname for the TRS-80 Color Computer, which despite its name, shares absolutely nothing with the TRS-80. Its BASIC version is called Color BASIC, which like many others was based on Microsoft BASIC, so the video’s description should be valid for many other BASIC versions as well. In the video we’re first taken through a basic summary of what the floating point format is all about, before running through an example of the algorithm used by Color BASIC for its RND function, using a test program written in Color BASIC.

As described in the video, the used algorithm appears to be the linear congruential generator, which is a pseudo-random generator that requires minimal resources from the hardware it runs on. Of course, its main disadvantage is that it will fairly rapidly begin to repeat itself, especially with a limited number of output bits. This makes it a decent choice even today for something like simple game logic where you just want to get some variation without aiming for cryptographically secure levels of randomness.

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A History Of The Tandy Computers

July 15, 2025 by Al Williams 22 Comments

Radio Shack, despite being gone for a number of years, is still in our cultural consciousness. But do you know Tandy? And did you ever wonder how a leather company that started in 1919 became, briefly, a computer giant? Or even an electronics retailer? [Abort Retry Fail] has the story in three parts, framed with their computers. Well, three parts so far. They are only up to the Tandy 1000.

At first, the company made parts for shoes. But after World War II, they found that catering to leather crafting hobbyists was lucrative. Within a few years, they’d opened stores across the country, making sure that the store managers owned 25% of their stores, even if it meant they had to borrow money from the home office to do so. Meanwhile, Radio Shack was in Boston selling to radio amateurs. By 1935, Radio Shack was a corporation. In 1954, they started selling “Realist” brand equipment, that we would come to know as Realistic.

In 1961, Tandy decided to branch out into other hobby markets, including radio hobbyists. But Radio Shack, dabbling in consumer credit, was sunk with $800,000 of uncollectable consumer credit.

In 1963, Tandy purchased the struggling Radio Shack for $300,000, which was a substantial amount of money in those days. Tandy immediately set about making Radio Shack profitable. Tandy would eventually split into three companies, spinning off its original leather and craft businesses.

Then came computers. If you are at all interested in the history of early computers, the TRS-80, or any of the other Radio Shack computers, you’ll enjoy the story. It wasn’t all smooth sailing. We can’t wait to read part four, although sadly, we know how the story ends.

We don’t just miss the Radio Shack computers. We loved P-Box kits. Yeah, we know someone bought the brand. But if you visit the site, you’ll see it just isn’t the same.

Behind RadioShack’s Cheapest Computer

June 30, 2025 by Bryan Cockfield 30 Comments

In the 1980s, there was a truly staggering amount of choice for a consumer looking to purchase a home computer. On the high end, something like an Apple Lisa, a business-class IBM PC, or a workstation from Sun Microsystems could easily range from $6,000 to $20,000 (not adjusted for inflation). For the time, these mind-blowing prices might have been worth the cost, but for those not willing to mortgage their homes for their computing needs, there were also some entry-level options. One of these was the Sinclair ZX-80, which was priced at an astounding $100, which caused RadioShack to have a bit of a panic and release this version of the TRS-80 computer to compete with it.

As [David] explains in his deep dive into this somewhat obscure machine, the TRS-80 MC-10 was a commercial failure, although not for want of features. It had a color display, a chicklet keyboard, and 4K of RAM, which were all things that the ZX-80 lacked.

Unfortunately, it also had a number of drawbacks compared to some of its other contemporaries that made consumers turn away. Other offerings by Commodore, Atari, Texas Instruments, and even RadioShack themselves were only marginally more expensive and had many more features, including larger memory and better storage and peripheral options, so most people chose these options instead.

The TRS-80 MC-10 is largely a relic of the saturated 80s home computer market. It’s drop in price to below $50, and the price competition between other PC manufacturers at the time was part of the reason for the video game crash of the 1980s, and even led to Steve Jobs getting fired from Apple. There’s not a huge retro scene for these machines either, although there is at least one game developer you can see in the video below from [Spriteworx]. If you want to experiment with some of the standard TRS-80 software, there are emulators that have everything you need.

Thanks to [Stephen] for the tip!

It’s MIDI For The TRS-80!

June 1, 2025 by Lewin Day 16 Comments

The Radio Shack TRS-80 was a much-loved machine across America. However, one thing it lacked was MIDI. That’s not so strange given the era it was released in, of course. Nevertheless, [Michael Wessel] has seen fit to correct this by creating the MIDI/80—a soundcard and MIDI interface for this old-school beast.

The core of the build is a BluePill STM32F103C8T6 microcontroller, running at a mighty 75 MHz. Plugged into the TRS-80s expansion port, the microcontroller is responsible for talking to the computer and translating incoming and outgoing MIDI signals as needed. Naturally, you can equip it with full-size classic DIN sockets for MIDI IN and MIDI OUT using an Adafruit breakout module. None of that MIDI Thru nonsense, though, that just makes people uncomfortable. The card is fully capable of reproducing General MIDI sounds, too, either via plugging in a Waveblaster sound module to the relevant header, or by hooking up a Roland Sound Canvas or similar to the MIDI/80s MIDI Out socket. Software-wise, there’s already a whole MIDI ecosystem developing around this new hardware. There’s a TRS-80 drum tracker and a synthesizer program, all with demo songs included. Compatibility wise, The MIDI/80 works with the TRS-80 Model I, III, and 4.

Does this mean the TRS-80 will become a new darling of the tracker and chiptune communities? We can only hope so! Meanwhile, if you want more background on this famous machine, we’ve looked into that, too. Video after the break.

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Hacky Shack? The TRS-80 Model I Story

May 8, 2025 by Maya Posch 44 Comments

The 1970s saw a veritable goldrush to corner the home computer market, with Tandy’s Z80-powered TRS-80 probably one of the most (in)famous entries. Designed from the ground up to be as cheap as possible, the original (Model I) TRS-80 cut all corners management could get away with. The story of the TRS-80 Model I is the subject of a recent video by the [Little Car] YouTube channel.

Having the TRS-80 sold as an assembled computer was not a given, as kits were rather common back then, especially since Tandy’s Radio Shack stores had their roots in selling radio kits and the like, not computer systems. Ultimately the system was built around the lower-end 1.78 MHz Z80 MPU with the rudimentary Level I BASIC (later updated to Level II), though with a memory layout that made running the likes of CP/M impossible. The Model II would be sold later as a dedicated business machine, with the Model III being the actual upgrade to the Model I. You could also absolutely access online services like those of Compuserve on your TRS-80.

While it was appreciated that the TRS-80 (lovingly called the ‘Trash-80’ by some) had a real keyboard instead of a cheap membrane keyboard, the rest of the Model I hardware had plenty of issues, and new FCC regulations meant that the Model III was required as the Model I produced enough EMI to drown out nearby radios. Despite this, the Model I put Tandy on the map of home computers, opened the world of computing to many children and adults, with subsequent Tandy TRS-80 computers being released until 1991 with the Model 4.

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Illustrated Kristina with an IBM Model M keyboard floating between her hands.

Keebin’ With Kristina: The One With The Hardware-Layered Keyboard

January 20, 2025 by Kristina Panos 6 Comments

You know (or maybe you didn’t), I get super excited when y’all use the links at the bottom of this round-up we call Keebin’ to communicate with your old pal Kristina about your various labors of love. So just remember that.

Case in point: I was typing up this very issue when I heard from [Jay Crutti] and [Marcel Erz]. Both are out there making replacement keyboards for TRS-80s — [Jay] for Models 3 and 4, and [Marcel] for the Model 1. Oooh, I said to myself. This is going at the top.

A TRS-80 Model 4 with a replacement keyboard. — A TRS-80 Model 4. Image by [Jay Crutti] via JayCrutti.com

Relevant tangent time: I remember in the 90s having a pile of computers in my parents’ basement of various vintages, a TRS-80 Model 2 among them. (Did I ever tell you about the time I got pulled over for speeding with a bunch of different computers in the backseat? I was like no, officer, first of all, those are old machines that no one would really want, and I swear I didn’t steal them.)

I think the TRS-80 is probably the one I miss the most. If I still had it, you can bet I would be using [Jay] and [Marcel]’s work to build my own replacement keyboard, which the 40-year-old machine would likely need at this point if the Model 4 is any indication with its failing keyboard contacts.

To create the replacements, [Jay] used Keyboard Layout Editor (KLE), Plate & Case Builder, and EasyEDA. Using the schematic from the maintenance manual, he matched the row/column wiring of the original matrix with Cherry MX footprints. Be sure to check out [Jay]’s site for a link to the project files, or to purchase parts or an assembled keyboard. On the hunt for TRS-80 parts in general? Look no further than [Marcel]’s site.
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