Author: Al Williams

4292 Articles

This Reactor Is On Fire! Literally…

October 29, 2025 by 51 Comments

If I mention nuclear reactor accidents, you’d probably think of Three Mile Island, Fukushima, or maybe Chernobyl (or, now, Chornobyl). But there have been others that, for whatever reason, aren’t as well publicized. Did you know there is an International Nuclear Event Scale? Like the Richter scale, but for nuclear events. A zero on the scale is a little oopsie. A seven is like Chernobyl or Fukushima, the only two such events at that scale so far. Three Mile Island and the event you’ll read about in this post were both level five events. That other level five event? The Windscale fire incident in October of 1957.

If you imagine this might have something to do with the Cold War, you are correct. It all started back in the 1940s. The British decided they needed a nuclear bomb project and started their version of the Manhattan Project called “Tube Alloys.” But in 1943, they decided to merge the project with the American program.

The British, rightfully so, saw themselves as co-creators of the first two atomic bombs. However, in post-World War paranoia, the United States shut down all cooperation on atomic secrets with the 1946 McMahon Act.

We Are Not Amused

The British were not amused and knew that to secure a future seat at the world table, it would need to develop its own nuclear capability, so it resurrected Tube Alloys. If you want a detour about the history of Britan’s bomb program, the BBC has a video for you that you can see below.

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Expert Systems: The Dawn Of AI

October 29, 2025 by 18 Comments

We’ll be honest. If you had told us a few decades ago we’d teach computers to do what we want, it would work some of the time, and you wouldn’t really be able to explain or predict exactly what it was going to do, we’d have thought you were crazy. Why not just get a person? But the dream of AI goes back to the earliest days of computers or even further, if you count Samuel Butler’s letter from 1863 musing on machines evolving into life, a theme he would revisit in the 1872 book Erewhon.

Of course, early real-life AI was nothing like you wanted. Eliza seemed pretty conversational, but you could quickly confuse the program. Hexapawn learned how to play an extremely simplified version of chess, but you could just as easily teach it to lose.

But the real AI work that looked promising was the field of expert systems. Unlike our current AI friends, expert systems were highly predictable. Of course, like any computer program, they could be wrong, but if they were, you could figure out why.

Experts?

As the name implies, expert systems drew from human experts. In theory, a specialized person known as a “knowledge engineer” would work with a human expert to distill his or her knowledge down to an essential form that the computer could handle.

This could range from the simple to the fiendishly complex, and if you think it was hard to do well, you aren’t wrong. Before getting into details, an example will help you follow how it works.

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Remembering Better Mono Graphics

October 27, 2025 by 11 Comments

No matter what kind of computer or phone you are reading this on, it probably has a graphics system that would have been a powerful computer on its own back in the 1980s. When the IBM PC came out, you had two choices: the CGA card if you wanted color graphics, or the MDA if you wanted text. Today, you might think: no contest, we want color. But the MDA was cheaper and had significantly higher resolution, which was easier to read. But as free markets do, companies see gaps and they fill them. That’s how we got the Hercules card, which supported high-resolution monochrome text but also provided a graphics mode. [The 8-bit Guy] has a look at these old cards and how they were different from their peers.

Actually, the original MDA card could do eight colors, but no one knew because there weren’t any monitors it could work with, and it was a secret. The CGA resolution was a whopping 640×200, while the MDA was slightly better at 720×350. If you did the Hercules card, you got the same 720×350 MDA resolution, but also a 720×348 graphics mode. Besides that, you could keep your monitor (don’t forget that, in those days, monitors typically required a specific input and were costly).

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Magazine Transistor Tester Lives Again

October 27, 2025 by 9 Comments

One of the lost pleasures of our modern world is the experience of going shopping at a grocery store, a mall, or a drugstore, and finding this month’s electronics magazine festooned with projects that you might like to build. Sure, you can find anything on the Internet, but there’s something to be said about the element of surprise. Can any of those old projects still be of interest?

[Bettina Neumryr] thinks so. She has a hobby of finding old magazine projects and building them. Her most recent installment is a transistor tester from the June 1983 issue of Everyday Electronics.

The tester was quite a neat job for 1983, with a neat case and a PC board. It measures beta and leakage. There’s an analog meter that can measure the collector current for a fixed base current (beta or hfe). Leakage is how much current flows between emitter and collector with the base turned off.

In 1983, we’d have loved to have a laser printer to do toner transfer for the PC board, but of course, that was unheard of in hobby circles of the day. The tester seemed to work right off the bat, although there was a small adjustment necessary to calibrate the device. All that was left was to put it in a period-appropriate box with some printed labels.

We loved the old electronics and computer magazines. Usually, when we see someone working on an old magazine project, it is probably not quite a literal copy of it. But either way is cool.

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VFETs Are (Almost) Solid State Tubes

October 26, 2025 by 9 Comments

We always enjoy videos from [w2aew]. His recent entry looks at vertical or VFETs, which are, as he puts it, a JFET that thinks it is a triode. He clearly explains how the transistor works as a conductor unless you bias the gate to form a depletion zone.

The transistors have a short channel, which means they conduct quite well. The low gate resistance and capacitance mean the devices can also switch very quickly. These devices were once in vogue for audio applications. However, they’d fallen out of favor until recently. The reason is that they work quite well in switching power supplies.

How good is the on resistance? So good that his meter reported the probes were shorted instead of measuring the resistance. Pretty good. We’ve seen these VFET transistors used as switches to drive magnetic field coils many years ago and they replaced much more complex circuitry.

The curve tracer in the video is a beautiful instrument of its own. The digital displays give it a high tech yet retro look. A curve tracer, if you haven’t used one, plots stepped voltages against current flowing, and is very useful for examining semiconductor devices. While not as fancy, it is possible to make one to connect to a scope quite easily.

We are pretty sure that it is a Tektronix 576. We watched a repair of a similar unit, the 577, if you’d like to see some (probably) similar insides.

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Examining The First Mechanical Calculator

October 26, 2025 by 9 Comments

Blaise Pascal is known for a number of things, but we remember him best for the Pascaline, an early mechanical calculator. [Chris Staecker] got a chance to take a close look at one, which is quite a feat since there were only about 20 made, and today we only know where nine of them wound up.

This Pascaline was lost for many years, and turned up in an antique store, where they thought it was a music box of some kind. The recent owner passed away, and now this machine is going to go up for auction, probably for more than we can afford. While he wasn’t able to handle the antique, he has plenty of knock-offs that were made back when people actually used them, which wasn’t that long ago. One of these is transparent, so you can see the mechanism inside.

The idea is to use the wheels like an old-fashioned phone dial to add counts to an output wheel. A linkage moves the next input wheel every time the current output wheel passes nine. Of course, if you have a multi-digit carry, it might take a little more elbow grease than just flipping the dial one normal position.

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Spreadsheets Apple ][ Style

October 26, 2025 by 9 Comments

It is hard to remember a time when no one had a spreadsheet. Sure, you had big paper ledgers if you were an accountant. But most people just scribbled their math on note paper or, maybe, an engineering pad. [Christopher Drum] wanted to look at what the state of the art in 1978 spreadsheet technology could do. So he ran VisiCalc.

Surprisingly, VisiCalc got a lot of things right that we still use today. One thing we don’t see much of is the text-based menu. As [Christopher] puts it, when you press the slash key, “what first appears to be ‘the entire alphabet’ pops up at the top of the screen.” In reality, it is a menu of letters that each correspond to some command. For example, C will clear the sheet (after prompting you, of course).

Interestingly, VisiCalc of the day didn’t do a natural order of evaluation. It would process by rows or by columns, your choice. So if cell A1 depended on cell B5, you’d probably get a wrong answer since A1 would always be computed before B5. Interestingly, the old Apple didn’t have up and down keys, so you had to toggle what the right and left keys did using the space bar. Different times!

This is a great look into a very influential piece of software and its tutorials. If you have old VisiCalc files you want to drag into the 21st century, [Christopher] explains the convoluted process to get mostly there.

We’ve been known to abuse spreadsheets pretty badly, although we’ve seen worse.