The Height Of 1960s Dental Electronic Technology

November 9, 2023 by Jenny List 9 Comments

If you’ve ever been to the dental surgery and found yourself requiring some gum surgery, the chances are you’ll have found your dentist wielding an electronic probe to cauterise the flesh. It’s evidently some form of RF device because you are usually required to hold one of the electrodes while it’s being used, but annoyingly, for an engineer, it’s hardly the time or place to ask how it works. For the curious, then, [Keri Szafir] has the box of tricks behind the probe and is subjecting it to a teardown.

The box on her bench isn’t the one you’ll find in your dentist’s toolkit today, but its distant ancestor from the 1960s that integrates multiple functions into a single box. It’s a very period enclosure with typically 1960s-style vacuum tubes and point-to-point wiring. There’s an HF oscillator using a pair of EL81 power pentodes for that electrode you always wished you could ask your dentist about, and unexpectedly, a thyratron, a type of gas-filled switching tube not dissimilar to a thyristor, in a separate circuit for dental pulp testing. We’re not dental experts here at Hackaday, but [Keri] has done the research and explains the device in the video below the break. At one point, she observes that it’s quite a scary machine to be connected to a living person, and we can concur with that.

Her bench has provided a few projects here in the past, including one of her amplifiers. While it might be fun to tear down a more modern version, you are better off asking for old dental burrs.

Continue reading “The Height Of 1960s Dental Electronic Technology” →

Just How Dodgy Are Cheap USB Chargers Anyway?

November 3, 2023 by Dan Maloney 49 Comments

Aside from apparently having both the ability to reproduce on their own and simultaneously never being around when you need one, USB chargers seem innocuous enough. The specs are simple: convert mains voltage to 5 volts, and don’t kill anyone while doing it. Both specs are typically met by most designs, but judging by [DiodeGoneWild]’s latest USB charger teardown, the latter only just barely, and with a whole lot of luck.

The sad state of plug-in USB power supplies is one of [DiodeGoneWild]’s pet gripes, and deservedly so. Most USB chargers cram a lot of electronics into a mighty small volume, and are built to a price point, meaning that something has to give in the design. In the case of the two units he tears apart in the video below, it’s pretty clear where the compromises are. Neither unit met the specs on the label in terms of current supplied and voltage regulation, even the apparently more capable quick charger, which is the first to go under the knife. The PCB within holds some alarming surprises, like the minimal physical isolation between the mains part of the circuit and the low-voltage section, but the real treat is the Schottky diode that gets up to 170°C under full load. Safety tip: when you smell plastic burning, throw the thing out.

The second charger didn’t fare any better; although it didn’t overheat, that’s mainly because it shut itself off before it could deliver a fraction of its rated 1 amp output. The PCB construction was shoddy in the extreme, with a squiggly trace standing in for a proper fuse and a fraction of a millimeter separation between primary and secondary traces. The flyback transformer was a treat, too; who doesn’t want to rely on a whisper-thin layer of cheap lacquer to keep mains voltage out of your phone?

All in all, these designs are horrible, and we have to thank [DiodeGoneWild] for the nightmares we’ll have whenever we plug into one of these things from now on. On the other hand, this was a great introduction to switch-mode power supply designs, and what not to do with our own builds. Continue reading “Just How Dodgy Are Cheap USB Chargers Anyway?” →

Pocket Calculator Isn’t A Brain Or Magic

October 20, 2023 by Al Williams 18 Comments

If you predate the pocket calculator, you may remember slide rules. But slide rules take a a little skill to use. There was a market for other devices that were simpler or, in some cases, cheaper. One common one was the “magic brain” or Addiator which was a little metal box with some slots that could add numbers. However, using clever tricks it could also subtract and — in a fashion — multiply. [Our Own Devices] has a teardown of the device you can see in the video below. It is deceptively simple, and the description of how it works is at least as interesting as the peek inside.

We remember these on the market and, honestly, always thought they were simple tally mechanisms. It turns out they are both less and more than that. Internally, the device is a few serrated sheet metal strips in a plastic channel. The subtraction uses a complement addition similar to how you do binary subtraction using 2’s complement math. Multiplication is just repetitive addition, which is fine for simple problems.

Continue reading “Pocket Calculator Isn’t A Brain Or Magic” →

An Explosive Look At Detonators

October 20, 2023 by Al Williams 17 Comments

If you’ve ever watched a cartoon where something blows up, you’ve probably seen a detonator — the device with a plunger that, when you push it, some dynamite blows up a bridge or a building or whatever. Detonators may be common in cartoons, but they are very real, and [Our Own Device] talks about some vintage detonators and, along the way, gives a brief history of explosive compounds.

For many years, black powder — a low explosive — was the only game in town. But a flurry of scientific advances brought a new class of high explosives far more powerful than gunpowder. The story of antique explosive factory safety measures, and lack thereof, is also an interesting side detour.

We enjoyed the trip down memory lane. However, if you want to skip the history lesson, jump about 17 minutes in to get a better look at the hardware. The teardown follows soon thereafter. These boxes are built solidly and have many safety features to prevent accidental detonations. One is a dynamo device with some clever mechanisms to ensure that the unit produces enough voltage, the other uses a charged capacitor.

Our usual interest in pyrotechnics is usually aimed more at fireworks. You think of explosives as having an imprecise effect, but that isn’t necessarily the case.

Continue reading “An Explosive Look At Detonators” →

Vector Network Analyzer Demo And Teardown

October 18, 2023 by Donald Papp 10 Comments

[Kerry Wong], ever interested in trying out and tearing down electrical devices, demonstrates and examines the SV 6301a Handheld Vector Network Analyzer. He puts the machine through its paces, noting that the 7 inch touchscreen is a pretty nice feature for those whose eyesight isn’t quite what it used to be.

The internals are similar to the nanoVNA-F V3, but not identical.

What’s a Vector Network Analyzer (VNA)? It’s not for testing Ethernet or WiFi. It’s aimed at a more classical type of “network”. The VNA tests and evaluates characteristics of electrical networks, especially as related to RF and microwave.

It provides detailed information about properties across a specified frequency range, making it an indispensable tool for advanced work. Tektronix has a resource page that goes into detail about exactly what kinds of things a VNA is good for.

[Kerry] shows off a few different features and sample tests before pulling the unit apart. In the end, he’s satisfied with the features and performance of the device, especially the large screen and sensible user interface.

After all, not every piece of test equipment does a great job at fulfilling its primary function, like the cheap oscilloscope that was a perhaps a little too cheap.

Continue reading “Vector Network Analyzer Demo And Teardown” →

Ready For The Rapture: This Wind-Up Cassette Player Can Play Anywhere

October 17, 2023 by Maya Posch 35 Comments

As useful as electronics are, the need to have some source of power for them can be a bit of an issue, especially for small, portable devices. One of the most low-tech but universally applicable source is human mechanical power, as demonstrated by the rugged 1980s-era Messenger II tape player in a recent [TechMoan] video. Without beating around the bush, this is indeed a device created by an evangelical organization (GRN) that missionaries would take with them to wherever their mission took them. Naturally this put the availability of power from a wall outlet in question, especially in the 1980s when this tape player was produced. Continue reading “Ready For The Rapture: This Wind-Up Cassette Player Can Play Anywhere” →

A Look At A 1960s Tube-Based Magnavox Concert Grand Console Stereo

October 16, 2023 by Maya Posch 31 Comments

Back in presumably the early 1960s, [David]’s grandfather bought a console stereo featuring a record player, AM/FM radio and a rather astounding stereo speaker system that would be more than enough to cover a small concert hall. Having inherited this piece of auditory art after his grandfather’s passing, [David] has given the console stereo a prominent place in his living room, which is where we start the tour in a new video on the [Usagi Electric] YouTube channel.

Plentiful I/O on this 1960s vintage piece of Magnavox audio equipment.

Being a 1950s-vintage design that got produced into the 1960s in a variety of models, the Magnavox Concert Grand is an all-tube affair, with the only presence of semiconductors being the three transistors found in the ‘Phantom’ remote control. [David] unfortunately does not posses this remote control, although the receiver module is present in the unit. It appears to be similar to the 1960 1ST800F in possession by [electra225] over at the Classic HiFi Care forum, which can provide 50 Watt per channel, yet as noted in the forum post, the 44 tubes alone draw about 250 Watt, with [electra225] recording 377 Watt total with everything cranked up. Clearly a high power bill was a price one had to pay for having high-end audio back in that era.

After [David] takes his unit apart – made very easy due to the modular construction – he goes through the basic circuitry of the power supply, the amplifiers and even has a peek at the circuitry of the remote control which appears to use basic frequency modulation to transfer the intended action to the receiver. All of this is made quite easy as full schematics are available for the entire system, as was standard back in those days. Interesting is also the I/O module, which features an MPX section, for demodulating stereo FM which wasn’t standardized yet at the time. Finally, tape drive connectors are available, which would have been likely a reel-to-reel unit for maximum HiFi enjoyment.

With the only broken thing in [David]’s unit being the snapped wire on the tuner of the radio module (ironically caused by the disassembly), all that was changed before reassembly was a good clean, after which the console stereo was put back and tested. Reflecting an era when HiFi equipment was supposed to blend in with other furniture, it will likely continue to do service for [David] as the world’s fanciest TV soundbar for the foreseeable future.

Continue reading “A Look At A 1960s Tube-Based Magnavox Concert Grand Console Stereo” →