Teardown

436 Articles

Life Imitates ART (ART-13, That Is)

November 23, 2023 by 4 Comments

[Mr. Carlson] has been restoring vintage military radios, and as part of his quest, he received an ART-13 transmitter. Before he opened the shipping box, he turned on the camera, and we get to watch from the very start in the video below. These transmitters were originally made by Collins for the Navy with an Army Air Corps variant made by Stewart-Warner. Even the Russians made a copy, presumably by studying salvaged units from crashed B-29s.

The transmitter puts out 100 watts at frequencies up to 18.1 MHz. The tubes needed a plate supply, and so, like many radios of the era, this one used a dynamotor. Think of it as a motor running at one voltage and turning a generator that produces a (usually) higher voltage. If you ever used a radio with one, you know you didn’t need an “on the air” sign — the whine of the thing spinning would let everyone know you had the key or microphone button pushed down. It’s an interesting piece of bygone tech that we’ve looked into previously.

The transmitter wasn’t in perfect shape, but we’ve seen worse. When the lid comes off, you can practically smell the old radio odor. There are tubes, coils, and even a vacuum relay, presumably for transmit/receive switching of the antenna. [Carlson] also tears open the dynamotor which is something you don’t see every day.

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Computer Gear With — Um — Gears

November 21, 2023 by 10 Comments

Analog computers have been around in some form for a very long time. One very obvious place they were used was in military vehicles. While submarine fire computers and the Norden bombsight get all the press, [msylvain59] has a lesser-known example: an M13A1 ballistic computer from an M48 tank that he tears down for us in the video below.

The M48, known as a Patton, saw service from 1952 to 1987. Just looking at the mechanical linkage to the tank’s systems is impressive. But inside, it is clear this is a genuinely analog computer. The thing is built — quite literally — like a tank. What was the last computer you opened that needed a hammer? And inside, you’ll find gears, bearings, and a chain!

We don’t pretend to understand all the workings. These devices often used gears and synchros (or selsyns, if you prefer) to track the position of some external thing. But we are guessing there was a lot more to it than that. It’s probably an exciting process to see something like that designed from scratch.

We did think of the Norden when we saw this. Hard to imagine, but there were “general purpose” analog computers.

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A Classic Shortwave Radio Restored

November 12, 2023 by 20 Comments

Before the Internet, if you wanted to hear news from around the world, you probably bought a shortwave receiver. In the golden age of world band radio, there was a great deal of high-quality programming on the shortwave bands and a large variety of consumer radios with shortwave bands. For example, the Sony CRF-160 that [M Caldeira] is restoring dates from the late 1960s or early 1970s and would have been a cool radio in its day. It retailed for about $250 in 1972, which sounds reasonable, but — don’t forget — in 1972 that would have been a 10% downpayment on a new car or enough to buy a Big Mac every day for a year with change left over.

As you can see in the video below, the radio seemed to work well right out of the gate, but the radio needed some rust removal and other sprucing up. However, it is an excellent teardown, with some tips about general restoration.

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The Height Of 1960s Dental Electronic Technology

November 9, 2023 by 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.

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Just How Dodgy Are Cheap USB Chargers Anyway?

November 3, 2023 by 48 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 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.

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An Explosive Look At Detonators

October 20, 2023 by 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.

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