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Hackaday Links: July 13, 2025

There’s interesting news out of Wyoming, where a coal mine was opened this week. But the fact that it’s the first new coal mine in 50 years isn’t the big news — it’s the mine’s abundance of rare earth elements that’s grabbing the headlines. As we’ve pointed out before, rare earth elements aren’t actually all that rare, they’re just widely distributed through the Earth’s crust, making them difficult to recover. But there are places where the concentration of rare earth metals like neodymium, dysprosium, scandium, and terbium is slightly higher than normal, making recovery a little less of a challenge. The Brook Mine outside of Sheridan, Wyoming is one such place, at least according to a Preliminary Economic Assessment performed by Ramaco Resources, the mining company that’s developing the deposit.

The PEA states that up to 1,200 tons of rare earth oxides will be produced a year, mainly from the “carbonaceous claystones and shales located above and below the coal seams.” That sounds like good news to us for a couple of reasons. First, clays and shales are relatively soft rocks, making it less energy- and time-intensive to recover massive amounts of raw material than it would be for harder rock types. But the fact that the rare earth elements aren’t locked inside the coal is what’s really exciting. If the REEs were in the coal itself, that would present something similar to the “gasoline problem” we’ve discussed before. Crude oil is a mixture of different hydrocarbons, so if you need one fraction, like diesel, but not another, like gasoline, perhaps because you’ve switched to electric vehicles, tough luck — the refining process still produces as much gasoline as the crude contains. In this case, it seems like the coal trapped between the REE-bearing layers is the primary economic driver for the mine, but if in the future the coal isn’t needed, the REEs could perhaps be harvested and the coal simply left behind to be buried in the ground whence it came.

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Remembering Heathkit

While most hams and hackers have at least heard of Heathkit, most people don’t know the strange origin story of the legendary company. [Ham Radio Gizmos] takes us all through the story.

In case you don’t remember, Heathkit produced everything from shortwave radios to color TVs to test equipment and even computers. But, for the most part, when you bought something from them, you didn’t get a finished product. You got a bag full of parts and truly amazing instructions about how to put them together. Why? Well, if you are reading Hackaday, you probably know why. But some people did it to learn more about electronics. Others were attracted by the lower prices you paid for some things if you built them yourself. Others just liked the challenge.

But Heathkit’s original kit wasn’t electronic at all. It was an airplane kit. Not a model airplane, it was an actual airplane. Edward Heath sold airplane kits at the affordable price around $1,000. In 1926, that was quite a bit of money, but apparently still less than a commercial airplane.

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A Magic Eye Tube Does All The Work In This Kit

We’re used to low cost parts and a diversity of electronic functions to choose from in our projects, to the extent that our antecedents would be green with envy. Back when tubes were king, electronics was a much more expensive pursuit with new parts, so designers had to be much more clever in their work. [Thomas Scherrer OZ2CPU] has just such a design on his bench, it’s a Heathkit Capaci-Tester designed in 1959, and we love it for the clever tricks it uses.

It’s typical of Heathkits of this era, with a sturdy chassis and components mounted on tag strips. As the name suggests, it’s a capacitor tester, and it uses a magic eye tube as its display. It’s looking for short circuits, open circuits, and low equivalent resistance, and it achieves this by looking at the loading the device under test places on a 19 MHz oscillator. But here comes that economy of parts; there’s no rectifier so the circuit runs on an AC HT voltage from a transformer, and that magic eye tube performs the task of oscillator as well as display.

He finds it to be in good condition in the video below the break, though he removes a capacitor placed from one of the mains input lines to chassis. It runs, and confirms his test capacitor is still good. It can’t measure the capacitance, but we’re guessing the resourceful engineer would also have constructed a bridge for that.

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Repairing An Old Heathkit ‘Scope

With so many cheap oscilloscopes out there, the market for old units isn’t what it used to be. But if you have a really old scope, like the Heathkit O-10 that [Ken] found in his basement, there is vintage cred to having one. [Ken’s] didn’t work, so a repair session ensued. You can see the results in the video below.

You can tell this is in an old scope — probably from the mid 1950s — because of its round tube with no graticle. Like many period scopes, the test probe input was just 5-way binding posts. The O-10 was the first Heathkit “O-series” scope that used printed circuit boards.

The device looked pretty good inside, except for a few dents. Of course, the box has tubes in it, so every power up test involves waiting for the tubes to warm up. [Ken] was very excited when he finally got a single green dot on the screen. That did, however, require a new CRT.

It wasn’t long after that he was able to put a waveform in and the scope did a good job of reproducing it. The unit would look good in an old movie, but might not be the most practical bench instrument these days.

These Heathkit scopes and their cousins were very popular in their day. The $70 price tag sounds cheap, but in the mid-1950s, that was about a month’s rent in a four-room house. While primitive by today’s standards, scopes had come a long way in 9 or 10 years.

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Classic Heathkit OL-1 Scope Gets Some TLC

These days, not only are oscilloscopes very common, but even a cheap instrument today would have been the envy of the world’s greatest labs not that long ago. But back in the day, the home experimenter basically had two choices: buy a surplus scope that a big company was getting rid of or build a Heathkit. [Radiotvphononut] bought an old Heathkit OL-1 scope at an estate sale and set about putting it back in service.

If you are used to a modern scope, you’ll be amazed at how simple a scope like this can be. A handful of tubes and a CRT is the bulk of it. Of course, the OL-1 is an analog scope with a 400 kHz bandwidth. It did, however, have two channels, which was a rarity at the time.

The OL-1 was sold for a few years up to 1956 and cost about $30 as a kit. There was a version with a larger screen (five whole inches) that cost an extra $40, so you can bet there were more OL-1s sold since $40 was a big ask in 1956. While they don’t seem like much today, you were probably the envy of the ham club in 1956 when you lugged this in for show and tell.

This is a long video, but it pays off at the end. Overall, this was a more capable scope than the $66 scope from 10 years earlier we looked at. Did you ever wonder how people visualized signals before the CRT? Funny, we did too.

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Heathkit Signal Generator Gets An Update

[DTSS_Smudge] correctly intuits that if you are interested in an old Heathkit signal generator, you probably already know how to solder. So, in a recent video, he focused on the components he decided to update for safety and other reasons. Meanwhile, we get treated to a nice teardown of this iconic piece of test gear.

If you didn’t grow up in the 1960s, it seems strange that the device has a polarized line cord with one end connected to the chassis. But that used to be quite common, just like kids didn’t wear helmets on bikes in those days.

A lot of TVs were “hot chassis” back then, too. We were always taught to touch the chassis with the back of your hand first. That way, if you get a shock, the associated muscle contraction will pull your hand away from the electricity. Touching it normally will make you grip the offending chassis hard, and you probably won’t be able to let go until someone kindly pulls the plug or a fuse blows.

These signal generators were very common back in the day. A lot of Heathkit gear was very serviceable and more affordable than the commercial alternatives. In 1970, these cost about $32 as a kit or $60 already built. While $32 doesn’t sound like much, it is equivalent to $260 today, so not an impulse buy.

Some of the parts are simply irreplaceable. The variable capacitor would be tough to source since it is a special type. The coils would also be tough to find replacements, although you might have luck rewinding them if it were necessary.

We are spoiled today with so many cheap quality instruments available. However, there was something satisfying about building your own gear and it certainly helped if you ever had to fix it.

There was so much Heathkit gear around that even though they’ve been gone for years, you still see quite a few units in use. Not all of their gear had tubes, but some of our favorite ones did.

Steel Reinforcement Toughens Cracked Vintage Knobs

Nothing can ruin a restoration project faster than broken knobs. Sure, that old “boat anchor” ham rig will work just fine with some modern knobs, but few and far between are the vintage electronics buffs that will settle for such aesthetic affrontery. But with new old stock knobs commanding dear prices, what’s the budget-conscious restorationist to do? Why, fix the cracked knobs yourself, of course.

At least that’s what [Level UP EE Lab] tried with his vintage Heahkit DX60 ham transmitter, with pretty impressive results. The knobs on this early-60s radio had all cracked thanks to years of over-tightening the set screws. To strengthen the knobs, he found some shaft collars with a 1/4″ inside diameter and an appropriate set screw. The backside of the knob was milled out to make room for the insert, which was then glued firmly in place with everyone’s go-to adhesive, JB Weld. [Level UP] chose the “Plastibonder” product, which turns out not to be an epoxy but rather a two-part urethane resin, which despite some initial difficulties flowed nicely around the shaft collar and filled the milled-out space inside the knob. The resin also flowed into the channels milled into the outside diameter of the shaft collars, which are intended to grip the hardened resin better and prevent future knob spinning.

It’s a pretty straightforward repair if a bit fussy, but the result is knobs that perfectly match the radio and still have the patina of 60-plus years of use. We’ll keep this technique in mind for our next restoration, or even just an everyday repair. Of course, for less demanding applications, there are always 3D printed knobs.

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