How any string instrument sounds depends on hundreds of factors; even the tiniest details matter. Seemingly inconsequential things like whether the tree that the wood came from grew on the north slope or south slope of a particular valley make a difference, at least to the trained ear. Add electronics into the mix, as with electric guitars, and that’s a whole other level of choices that directly influence the sound.

To experiment with that, [Mark Gutierrez] tried rolling some home-brew capacitors for his electric guitar. The cap in question is part of the guitar’s tone circuit, which along with a potentiometer forms a variable low-pass filter. A rich folklore has developed over the years around these circuits and the best way to implement them, and there are any number of commercially available capacitors with the appropriate mojo you can use, for a price.

[Mark]’s take on the tone cap is made with two narrow strips of regular aluminum foil separated by two wider strips of tissue paper, the kind that finds its way into shirt boxes at Christmas. Each of the foil strips gets wrapped around and crimped to a wire lead before the paper is sandwiched between. The whole thing is rolled up into a loose cylinder and soaked in mineral oil, which serves as a dielectric.

To hold the oily jelly roll together, [Mark] tried both and outer skin of heat-shrink tubing with the ends sealed by hot glue, and a 3D printed cylinder. He also experimented with a wax coating to keep the oily bits contained. The video below shows the build process as well as tests of the homebrew cap against a $28 commercial equivalent. There’s a clear difference in tone compared to switching the cap out of the circuit, as well as an audible difference in tone between the two caps. We’ll leave the discussion of which sounds better to those with more qualified ears; fools rush in, after all.

Whatever you think of the sound, it’s pretty cool that you can make working capacitors so easily. Just remember to mark the outer foil lead, lest you spoil everything.

Thanks to [Eric] for the tip.

Although much diminished now, the public switched telephone network was one of the largest machines ever constructed. To make good on its promise of instant communication across town or around the world, the network had to reach into every home and business, snake along poles to thousands of central offices, and hum through the ether on microwave links. In its heyday it was almost unfathomably complex, with calls potentially passing through thousands of electronic components, any of which failing could present anything from a minor annoyance to a matter of life or death.

The brief but very interesting film below deals with “The Tyranny of Large Numbers.” Produced sometime in the 1960s by Western Electric, the manufacturing arm of the Bell System, it takes a detailed look at the problems caused by scaling up systems. As an example, it focuses on the humble carbon film resistor, a component used by the millions in various pieces of telco gear. Getting the manufacturing of these simple but critical components right apparently took a lot of effort. Initially made by hand, a tedious and error-prone process briefly covered in the film, Western Electric looked for ways to scale up production significantly while simultaneously increasing quality.

While the equipment used by the Western engineers to automate the production of resistors, especially the Librascope LGP-30 computer that’s running the show, may look quaint, there’s a lot about the process that’s still used to this day. Vibratory bowl feeders for the ceramic cores, carbon deposition by hot methane, and an early version of a SCARA arm to sputter gold terminals on the core could all be used to produce precision resistors today. Even cutting the helical groove to trim the resistance is similar, although today it’s done with a laser instead of a grinding wheel. There are differences, of course; we doubt current resistor manufacturers look for leaks in the outer coating by submerging them in water and watching for bubbles, but that’s how they did it in the 60s.

The productivity results were impressive. Just replacing the silver paint used for terminal cups with sputtered gold terminals cut 16 hours of curing time out of the process. The overall throughput increased to 1,200 pieces per hour, an impressive number for such high-reliability precision components, some of which we’d wager were still in service well into the early 2000s. Most of them are likely long gone, but the shadows cast by these automated manufacturing processes stretch into our time, and probably far beyond.

Disappointing news this week for those longing for same-hour Amazon delivery as the retail giant tapped the brakes on its Prime Air drone deliveries. The pause is partially blamed on a December incident at the company’s Pendleton, Oregon test facility, where two MK30 delivery drones collided in midair during light rain conditions. A Bloomberg report states that the crash, which resulted in one of the drones catching fire on the ground, was due to a software error related to the weather. As a result, they decided to ground their entire fleet, which provides 60-minute delivery to test markets in Arizona and Texas, until a software update can be issued.

While we’ve always been skeptical about the practicality of drone delivery, it sure seems like Amazon is taking it seriously and making progress. There’s plenty of money to be made catering to the impatience of consumers and the general need for instant gratification, and where there’s potential for profit, technology is never far behind. So chances are good that someone will get this right, and with an infinite bucket of money and the ability to attract top talent, this is Amazon’s contest to lose. It is a bit alarming, though, that a little rain knocked these drones out of the air. We’d love to find out exactly what happened and how they plan to fix it.

Also in drone news, NATO has decided to deploy “drone boats” to help protect undersea cables and pipelines. A total of 20 uncrewed surface vehicles (USVs) will be deployed as part of Operation Baltic Sentry, which will include twelve crewed vessels and an unspecified number of patrol aircraft. The idea is to get eyes and ears on the infrastructure assets under the Baltic Sea, where a number of incidents have occurred over the last year or so, resulting in pipelines and undersea cables being damaged. That’s an understandable goal, but we’re keen on the USV itself. There’s not much information about them, and it’s not even clear which navy in the NATO bloc has these things. It’s also a little hard to tell how big they are, although our guess would be somewhere between a large patrol boat and a small cutter. We’d also like to know if these are remotely operated vessels or autonomous; again, our guess would be a mix of the two.

We got a tip this week about a post over on the Arduino forum with detailed instructions on making your own Dupont jumpers. There’s a link to a PDF with the pictorial guide, which shows exactly how to make these handy tools. Some people commented on this being a waste of time when you can buy jumpers on the cheap. But we’ve heard enough horror stories about those that rolling your own seems prudent. Plus we really liked the tips on crimping two leads into a single connector.

A few decades ago, there was a better-than-average chance that any band’s keyboardist was on mushrooms. Things have flipped, though, and now we’ve got shrooms on the keyboards. It comes to us from “Bionics and the Wire,” a Manchester, UK group that makes music with plants and mushrooms. There’s no detail on the equipment they use, but the business end of the instrument is a set of four solenoid-operated arms positioned over a keyboard. Electrodes are clipped to the caps of a couple of Wood Ear mushrooms, and whatever electrical signals they pick up are presumably passed to some amplifiers that figure out which notes to play. They claim the signals come from natural bioelectric activity in the fungi, but we suppose some of the signals may be coming from random electrical noise picked up by the mushrooms. Either way, the tune is pretty cool.

And finally, a while back we did a piece on electrical substations that took a look at all the cool stuff found in and around the big transformers that keep the grid running. One piece of gear that we read about but couldn’t find enough information on to include in the article was the Bucholz relay, a piece of protective gear that monitors the flow of dielectric oil inside these big transformers. Thankfully, the YouTube algorithm detected our frustration and suggested this cool video on how the Bucholz relay works. It’s remarkably simple, which is pretty much what you want for something that protects millions of dollars of irreplaceable infrastructure. The video also has a lot of nice details on the other bits and pieces inside a transformer. Enjoy!

Siphons are one of those physics phenomena that, like gyroscopes, non-Newtonian fluids, and electricity, seem almost magical. Thanks to atmospheric pressure, simply filling a tube with liquid and placing the end of the tube below the liquid level of a container allows it to flow against gravity, over a barrier, and down into another container without any extra energy inputs once the siphon is started. They’re not just tricks, though; siphons have practical applications as well, such as in siphon-powered hydroelectric turbine.

This is an iteration of [Beyond the Print]’s efforts to draw useful energy from a local dam with an uneconomic amount of water pressure and/or volume for a typical hydroelectric power station. One of his earlier attempts involved a water wheel but this siphon-based device uses a more efficient impeller design instead, and it also keeps the generator dry as well. Using 3″ PVC piping to channel the siphon, as well as a short length of thinner pipe to attach a shop vac for priming the siphon, water is drawn from the reservoir, up the pipe, and then down through the impeller which spins a small DC generator.

This design is generating about 9 V open-circuit, and we’d assume there’s enough power available to charge a phone or power a small microcontroller device. However, there’s a ton of room for improvement here. The major problem [Beyond the Print] is currently experiencing is getting air into the system and having the siphon broken, which he’s solved temporarily by adding a bucket at the outflow. This slows down the water though, so perhaps with any air leaks mitigated the power generation capabilities will be greatly increased.

For economic reasons, not every lake with a dam can support a hydroelectric power plant. Some rivers or creeks are dammed for flood control or simply for recreation, and don’t have the flow rate or aren’t deep enough to make the investment of a grid-scale generation facility worthwhile. But for those of us with a few spare parts around and access to a small lake, sometimes it’s possible to generate a usable amount of energy with just a bit of effort.

[Beyond the Tint] is building this mostly as a proof-of-concept, starting with a 1,000W hub motor from an e-bike that’s been removed from its wheel. A 3D-printed waterwheel attachment is installed in its place, and the fixed shaft is attached to a homemade ladder-looking mechanism that allows the entire generator to be lowered into the flow of a moving body of water, in this case, a small stream. A bridge rectifier converts the AC from the hub motor (now a generator) into DC, and after a few measurements and trials, [Beyond the Tint] produced over 30W with the first prototype.

A second prototype was made with feedback from the first video he produced, this time with an enclosed paddlewheel. This didn’t appear to make much difference at first, but a more refined impeller may make a difference in future prototypes. Small-scale hydropower is a fairly popular challenge to tackle, especially in the off-grid community. With access to even a small flowing stream and enough elevation change, it’s possible to build something like this generator out of parts from an old washing machine.

There’s a Blue Bendix in Texas, and thanks to [Usagi Electric] it’s the oldest operating computer in North America.  The Bendix G-15, a vacuum tube computer originally released in 1956, is now booting, and running code from paper tape. [David, aka Usagi] received the G-15 about a year ago from The System Source museum. The goal was to get the computer running so museum patrons could interact with a real tube computer. We’ve been following along since the project began.

[Usagi’s] latest G-15 video covers the last few problems on the road to running code. The biggest hurdle was the fact that the system wasn’t responding properly to the GO button on the typewriter. [Usagi] was able to isolate the issue down to a flip flop and then to a particular signal on an AND gate — the RC signal. The gate appeared to be bad, but swapping the entire circuit card multiple times had no effect. Something else had to be going on.

After hours of troubleshooting and a bit of hair-pulling, [Usagi] changed a diode circuit card downstream of the suspect card. This miraculously fixed the problem. It turned out the diode card had a tiny solder bridge since it was built in the 1950’s. This bridge put a heavy load on a buffer, causing grid leakage. For those of us who aren’t old [TubeTimers], grid leakage is a tiny current from the grid of a tube into the drive circuitry. Leakage is present on all triodes, and tube testers would often misdiagnose good tubes as bad for this reason.

Once the bridge and a few other problems were fixed, the machine sprang to life, not with a roar, but with a solid thunk as it slammed the incredibly wide typewriter carriage into a nearby shelf.  If you do nothing else this year, watch the video from the 20-minute mark. You get to see the pure joy a hacker gets when their project starts to work.

The Bendix was executing DIAPER — Diagnostic Program for Easy Repair. DIAPER runs a series of tests on the machine and rings a bell every time a test passes. Not a little bell in the typewriter, but a big 120 V beast hiding inside the computer itself. Ding, fries are done indeed!

[Usagi] did have some help this time around — thanks to a tip from [Avery] he contacted HP Agilent Keysight to inquire about a basic scope. Apparently, they know his videos and are huge fans of the Bendix because they sent him a really nice 4-channel digital oscilloscope. It definitely helped push the Bendix over the finish line! We love seeing companies give back to the community this way — and hope to see more in the future.

Now, this isn’t the last Bendix G-15 video from [Usagi]. There are several more tapes to run a full DIAPER test. The typewriter itself needs quite a lot of work before it will accept keystrokes, and we’re sure [Usagi] has a few more surprises up his sleeves.

You can still find a few tube computer projects floating around. You can even replace your 555 with some.