A Function Generator From The Past

October 10, 2025 by Jenny List 12 Comments

It’s always a pleasure to find a hardware hacker who you haven’t seen before, and page back through their work. [Bettina Neumryr]’s niche comes in building projects from old electronics magazines, and her latest, a function generator from the British Everyday Electronics magazine in April 1983, is a typical build.

The project uses the XR2206 function generator chip, a favourite of the time. It contains a current controlled oscillator and waveform shaper, and can easily produce square, triangle, and sine waves. It was always a puzzle back in the day why this chip existed as surely the global market for function generators can’t have been that large, however a little bit of background reading for this write-up reveals that its intended application was for producing frequency-shift-keyed sinusoidal tones.

The two PCBs on the bench, with a multimeter — Yellow-stained boards for the win!

The EE project pairs the XR2206 with an op-amp current generator to control the frequency, and another op-amp as an amplifier and signal conditioner. The power supply is typical of the time too, a mains transformer, rectifier, and linear regulators. There are a pair of very period PCBs supplied as print-outs in the magazine for home etching. This she duly does, though with toner transfer which would have been unheard of in 1983. After a few issues with faulty pots and a miswired switch, she has a working function generator which she puts in a very period project box.

It’s interesting to look at this and muse on what’s changed in electronic construction at our level in the last four decades. The PCB is single sided and has that characteristic yellow of ferric chloride etching, it takes up several times the space achievable with the same parts on the professionally-made dual-sided board designed using a modern PCB CAD package we’d use today. A modern take on the same project would probably use a microcontroller and a DAC, and a small switch-mode supply for less money than that transformer would provide the power. But we like the 1983 approach, and we commend [Bettina] for taking it on. The full video is below the break.

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Active Probe Reaches 3 GHz

September 26, 2025 by Al Williams 6 Comments

When you think of a scope probe, you usually think of what is basically a wire with a spring hook and an attenuator. Those are passive probes. [Kerry Wong] shows off a pre-release active probe that sidesteps some problems with those ordinary passive probes.

The trick is that passive probes have input capacitance that interferes with very high-frequency signals. They also tend to have less noise. Although the probe isn’t on the market yet, it is set to debut at a price lower than competitive probes. Still, be warned. The reason you don’t see them more often is that $1,000 is relatively inexpensive for an active probe.

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Tube Furnace Is The Real Hotness

September 25, 2025 by Al Williams 11 Comments

We aren’t sure what [theglassman] is working on, but based on his recent projects, we think it is probably something interesting. He’s been decapping ICs, growing oxide on silicon substrates, and has built a tube furnace capable of reaching 1200 °C.

What would you do with something that can melt cast iron? We aren’t sure, but maybe you’ll tell us in the comments. We do have a fair idea of what [theglassman] is doing, though.

The core of the oven is a quartz tube. Insulation is via refractory cement and alumina ceramic wool. The heating itself is classic Nichrome wire and a tiny thermocouple. The real key, though, is to the proper controller. [theglassman] suggests a ramp/soak controller. These allow you to program sequences that heat up and then stop, which, if done properly, can prevent your fragile quartz tube from cracking.

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Mandrel Magic: Small Box Assembly With 3D Printing

September 21, 2025 by Matt Varian 2 Comments

Often, we face tedious tasks with no way around them. Sometimes, you just have to grit your teeth and push through. But small tweaks can make the onerous task a bit easier to handle. [James Bowman] sent in his latest quick project that helps him fold small boxes more efficiently.

To fulfill orders on his previously covered TermDriver2, [James Bowman] is faced with folding thousands of small boxes. To aid in this daunting task, he had the idea of making a tool to streamline the process — every second saved adds up when you’re repeating a task thousands of times. He designed a 3D printed mandrel that pops the flat box blank open as it’s slid over the tapered top, shaping it into a perfect rectangle for easy folding of the top flaps.

The nice thing about 3D printng is how easy it is to iterate on a design. Once James had the first version printed and verified it worked as hoped, he had ideas to improve it, such as adding a second mandrel to twist the box from both the inside and outside and adding a guide on one side to enhance rigidity.

While we often think of 3D printers producing ready-to-use parts, but printed tooling holds great potential for repetitive tasks, and is a huge cost saver compared to traditional methods.

Two pieces of metal are sitting next to each other on a brick, with one edge touching. The copper end of a torch is directing a flame against the metal, and the metal is glowing brightly around the point where the flame contacts it.

Welding With Natural Gas And Oxygen

September 21, 2025 by Aaron Beckendorf 15 Comments

By virtue of its triple bond, acetylene burns hotter than any other common hydrocarbon when mixed with oxygen, but it isn’t the only flame hot enough for welding. With the assistance of a homemade oxygen concentrator, [Hyperspace Pirate] was able to make a natural gas torch that melts steel, even if welding with the torch remains difficult.

[Hyperspace Pirate] built his oxygen concentrator around a pressure-swing adsorption system, which uses two tanks of a molecular sieve to selectively adsorb and purge nitrogen, leaving behind mostly oxygen. [Hyperspace Pirate] used reverse-osmosis membrane casings as the tanks, solenoid valves to control gas flow, and an Arduino with some MOSFETs to control the timing. For fuel, he used a convenient source of natural gas, already installed in his garage: the water heater’s gas supply. Since the house’s meter regulates the gas down to a fairly low pressure, and the oxygen concentrator doesn’t produce high pressures, the torch didn’t need any inline regulators.

Inline check valves, on the other hand, were very much necessary, a mixture of oxygen and natural gas propagating back along the lines being undesirable for obvious reasons, and flashback arrestors would have been a good addition. [Hyperspace Pirate] built the torch itself out of copper tubing and needle valves, with a 0.9 mm MIG welder tip as the nozzle. Adjusting the gas mixture was mostly a matter of trial and error. With an oxygen-rich flame, it could cut thin metal decently well, but it tended to melt thick pieces more than it cut. On the other hand, even with a neutral flame, the water vapor in the exhaust oxidized steel, which made welding quite difficult, but not impossible.

The oxygen supply by itself was an entertaining tool, turning smoldering pieces of charcoal or steel wool violently incandescent. With the assistance of some steel wool, [Hyperspace Pirate] set a steel tube on fire. With a bit more oxygen, it would probably make an effective thermic lance. If you still want to do your welding with acetylene, he’s also made that before.

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Test Pattern Generator For SCART And RGB TVs

September 19, 2025 by Tyler August 4 Comments

CRTs don’t last forever, and neither do the electronics that drive them. When you have a screen starting to go wonky, then you need a way to troubleshoot which is at fault. A great tool for that is a pattern generator, but they’re not the easiest to come by these days. [baritonomarchetto] needed a pattern generator to help repair his favourite arcade machine, and decided to make his own DIY Portable RGB CRT Test Pattern Generator.

One of the test patterns available from the device. This TV appears to be in good working order.

While he does cite [Nicholas Murray]’s RP2040 test pattern generator as a starting point (which itself builds on the PicoVGA library once featured here), he couldn’t just build one. That worthy project only outputs VGA and because [baritonomarchetto] is in Europe, he needed a SCART connector. Since he’s working on arcade machines, he needed non-SCART RGB signals, too. The arcade signals need to be at higher voltages (TLL level) than the RGB signal you’d find in SCART and VGA.

The upshot is while he’s using [Nicholas]’s code for the RP2040, he’s rolled his own PCB, including a different resistor ladders to provide the correct voltages depending on if he’s dealing with a home TV or arcade CRT. To make life easier, the whole thing runs off a 9V battery.

If you’re wondering what the point of these test patterns is, check out this 1981-vintage pattern generator for some context from the era. If a digital replica doesn’t float your boat, it is possible to recreate the original analog circuitry that generated these patterns back when the CRT was king.

Dirty Pots, Meet Power Tools!

September 19, 2025 by Tyler August 26 Comments

Let’s face it, nobody likes scrubbing, but what option do you have? You can’t exactly break out the grinder to clean off the remains of last nights dinner… right? Well, maybe not a grinder, but thanks to this hack by [Markus Opitz], you can use an oscillating tool.

It’s a simple enough hack: [Markus] modeled the attachment for his Bosch oscillating tool in Tinkercad, and created a bracket to hold a large metal binder clip. The clip attaches with a screw, and can hold whatever scrubbing pad your carpel-tunnel afflicted hands can’t bear to hold on to. He’s using a self-cleaning stainless-steel sponge.

One nice touch is a pair of protective lips on the jaws of the metal clip, to keep it from accidentally scratching the delicate surface under care. Of course if you have a drill or a Dremel handy you can buy attachments for polishing disks of various grits, but what’s the fun in that? Doing the dishes with a hacked-together oscillating tool just somehow seems more fun. Plus this way you can’t accidentally produce an engine-turning pattern.

We don’t seem to have featured many hacks for these fun, buzzing, multi-purpose tools, so if you’ve got one send us a tip. We did feature an oscillating cutter for CNC once, but that was fully DIY.