If you are a connoisseur of analogue audio, it’s probable you might have a turntable and a stack of records at home somewhere. If you are of a certain age you may even have a cassette deck, though you’re more likely to have abandoned that format some time in the 1990s. If you are old enough to have been around in the 1960s or 1970s though, you may have owned another analogue audio format. One of several that you might have found in a well-equipped home of that period was the 8-track stereo cartridge, a self-contained tape cassette format that fit four stereo tracks onto a single quarter-inch tape loop as eight parallel tracks, four each of left and right. A triumph of marketing, really, it should more accurately have been called 4-track stereo.
8-track cartridges were developed from earlier tape cartridge formats, largely to satisfy the demands of the automotive industry for interchangeable in-car entertainment. Thus if you owned an 8-track player it was most likely to have been found in your car, but it was not uncommon to find them also incorporated into home hi-fi systems. Thus we come to our subject today. Our retrotechtacular series usually highlights a video showing a bygone technology, but today we’re going to get a little more hands-on.
Some time in the early 1990s, I acquired an 8-track player, a BSR McDonald unit manufactured in the UK and dating from the early 1970s. BSR were much more well-known for their turntables, so this is something of an oddity. Where I found it has disappeared into the mists of time, but it was probably at a radio rally or junk sale. I certainly didn’t buy it because I wanted it to play 8-track tapes, instead I wanted a talking point for my hi-fi, something quirky to set it apart from everyone else’s. So every incarnation of listening enjoyment chez List for the last quarter century has had an 8-track player nestling within it, even if it has never played a tape while in my ownership. Thus we have a unique opportunity for this retro teardown.
Transformerless power supplies are showing up a lot here on Hackaday, especially in inexpensive products where the cost of a transformer would add significantly to the BOM. But transformerless power supplies are a double-edged sword. That title? Not clickbait. Poking around in a transformerless-powered device can turn your oscilloscope into a smoking pile or get you electrocuted if you don’t understand them and take proper safety precautions.
But this isn’t a scare piece. Transformerless designs are great in their proper place, and you’re probably going to encounter one someday because they’re in everything from LED lightbulbs to IoT WiFi switches. We’re going to look at how they work, and how to design and work on them safely, because you never know when you might want to hack on one.
Here’s the punchline: transformerless power supplies are safely useable only in situations where the entire device can be enclosed and nobody can accidentally come in contact with any part of it. That means no physical electrical connections in or out — RF and IR are fair game. And when you work with one, you have to know that any part of the circuit can be at mains voltage. Now read on to see why!
We’ve seen a bunch of replacements for nixie tubes using LEDs and edge-lit acrylic for the numbers. But one of the earliest digital voltmeters used edge-lit Lucite plates for the numbers and a lot of incandescent lamps to light them up.
[stevenjohnson] has a Non-Linear Systems Model 481 digital voltmeter and he’s done a teardown of it so we can get a glimpse of the insides. Again, anyone who’s seen the modern versions of edge-lit numeric displays knows what they are: A series of clear plastic plates with numbers (or characters) etched into them, each with a light source beneath them. You turn one light on to light one plate, another to light another, and so on. The interesting bit here is the use of incandescent bulbs and the use of sequential relays to cycle through the lights. The relays make a lot of racket, especially with the case open.
[stevenjohnson] also notes that he might have made a mistake opening up the part of the machine where the plates are stored as it took him a bit to get the plates back in place and back in the unit. We’d imagine it was pretty loud if you were taking a lot of measurements with this machine, although it looks great inside and, obviously, the idea is a pretty good one. Check out this edge-lit nixie tube display or these edge-lit numeric modules.
The audio cassette is an audio format that presented a variety of engineering challenges during its tenure. One of the biggest at the time was that listeners had to physically remove the cassette and flip it over to listen to the full recording. Over the years, manufacturers developed a variety of “auto-reverse” systems that allowed a cassette deck to play a full tape without user intervention. This video covers how Akai did it – the hard way.
Towards the end of the cassette era, most manufacturers had decided on a relatively simple system of having the head assembly rotate while reversing the motor direction. Many years prior to this, however, Akai’s system involved a shuttle which carried the tape up to a rotating arm that flipped the cassette, before shuttling it back down and reinserting it into the deck.
Even a regular cassette player has an astounding level of complexity using simple electromechanical components — the humble cassette precedes the widespread introduction of integrated circuits, so things were done with motors, cams, levers, and switches instead. This device takes it to another level, and [Techmoan] does a great job of showing it in close-up detail. This is certainly a formidable design from an era that’s beginning to fade into history.
The video (found after the break) also does a great job of showing glimpses of other creative auto-reverse solutions — including one from Phillips that appears to rely on bouncing tapes through something vaguely resembling a playground slide. We’d love to see that one in action, too.
We’ve heard a lot about the Tesla Model S over the last few years, it’s a vehicle with a habit of being newsworthy. And as a fast luxury electric saloon car with a range of over 300 miles per charge depending on the model, its publicity is deserved, and that’s before we’ve even mentioned autonomous driving driver-assist. Even the best of the competing mass-produced electric cars of the moment look inferior beside it.
Tesla famously build their battery packs from standard 18650 lithium-ion cells, but it’s safe to say that the pack in the Model S has little in common with your laptop battery. Fortunately for those of a curious nature, [Jehu Garcia] has posted a video showing the folks at EV West tearing down a Model S pack from a scrap car, so we can follow them through its construction.
The most obvious thing about this pack is its sheer size, this is a large item that takes up most of the space under the car. We’re shown a previous generation Tesla pack for comparison, that is much smaller. Eye-watering performance and range come at a price, and we’re seeing it here in front of us.
The standard of construction appears to be very high indeed, which makes sense as this is not merely a performance part but a safety critical one. Owners of mobile phones beset by fires will testify to this, and the Tesla’s capacity for conflagration or electrical hazard is proportionately larger. The chassis and outer cover are held together by a huge array of bolts and Torx screws, and as they comment, each one is marked as having been tightened to a particular torque setting.
Under the cover is a second cover that is glued down, this needs to be carefully pried off to reveal the modules and their cells. The coolant is drained, and the modules disconnected. This last task is particularly hazardous, as the pack delivers hundreds of volts DC at a very low impedance. Then each of the sixteen packs can be carefully removed. The packs each contain 444 cells, the pack voltage is 24 V, and the energy stored is 5.3 kWh.
The video is below the break. We can’t help noticing some of the rather tasty automotive objects of desire in their lot.
There used to be a time, before running shoes had blinking LEDs and required placing on an inductive charger overnight, when we weren’t worried about whether or not we could dump the firmware running underneath our heels. Those are not the times that we’re living in. Nike came out with a shoe that solves the age-old problem of lacing: the HyperAdapt. And [Telind Bench] has torn them apart.
Honestly, we’re kinda “meh” about what’s inside. The “laces” are actually tubes with a small Kevlar-like cable running inside, and the whole thing torques up using a small, geared DC motor. That’s kinda cool. (We have real doubts about [Telind]’s guess of 36,000 RPM for the motor speed.) But in an age when Amazon gives away small WiFi-enabled devices for a few bucks as a loss-leader to get you to order a particular brand of laundry detergent, we’re not so dazzled by the technology here, especially not at the price of $720 for a pair of freaking shoes.
The only really interesting bit is the microcontroller, which is over-powered for the job of turning a wheel when a keyboard-style sensor is pressed by your heel. What is Nike thinking? We want to see the firmware, and we’d like it reverse engineered. What other chips are on board? Surely, they’ve got an accelerometer and are measuring your steps, probably tying in with an exercise app or something. Does anyone have more (technical) detail about these things? Want to make a name for yourself with a little stunt hacking?
It’s widely known that a smoke detector is a good ionizing radiation source, as they contain a small amount of americium-241, a side product of nuclear reactors. But what about other sources? [Carl Willis] got hold of an old Soviet era smoke detector and decided to tear it down and see what was inside. This, as he found out, isn’t something you should do lightly, as the one he used ended up containing an interesting mix of radioactive materials, including small amounts of plutonium-239, uranium-237, neptunium-237 and a selection of others. In true hacker fashion, he detected these with a gamma ray spectroscope he has in his spare bedroom, shielded from other sources with lead bricks and copper and tin sheets. Continue reading “Soviet Era Smoke Detector Torn Down, Revealing Plutonium”→