This is something we’ve been waiting a very long time for. The Church of Scientology uses devices called E-Meters to measure Thetans in the body. We’re not going to discuss this further, because we don’t want to be murdered. In reality, the E-Meter is simply a device that costs five thousand dollars and only measures the resistance of the human body. It does this by having the subject hold two copper cylinders and a simple Wheatstone bridge. Why does the E-Meter cost five thousand dollars? As [Play With Junk] found out, it’s an exquisitely engineered piece of hardware.
[Play With Junk] acquired this E-Meter from eBay for something around $100, and from a system-level analysis, it’s really not anything special. There’s a fancy analog meter, yes, but most of this wouldn’t be out of place in any 90s-era piece of test equipment. There’s an 8051 microcontroller reading what are probably some fancy ADCs, and there’s an LCD driver on board. Slap it in a fancy injection-molded case, and you have an E-Meter.
What’s most impressive is the quality of the components that go into a machine that effectively only measures the resistance of the human body. The ‘trim’ pot is a Vishay wire-wound precision potentiometer that costs somewhere between $20 and $60. The power switch is an over-specced switch that probably costs $5. The control pots look and feel great, and the wiring is wrapped around chokes.
This is an exceptionally well-engineered device, and it shows. There’s an incredible amount of work that went into the electronics, and a massive amount of money that went into the fancy injection molded enclosure. If you’re looking for an example of a well-engineered tool, price be damned, you need only look at an E-Meter.
As the package with its extremely heavy contents is first inspected, he reminds us just what a bomb hoist does, it is clipped to an aircraft by ground crew and serves as a small but extremely powerful crane to lift up to a 6000-pound piece of ordnance onto the wing pylon of an aircraft. This particular example dates from the 1960s, and features a 28-volt DC motor coupled to a bulky gearbox assembly on a swivel mount for attachment.
His teardown is extremely detailed, but such is the engineering and complexity of the device you’ll want to read every part of it. The motor is a fairly traditional separately-excited brushed DC design such as you’d expect from that era, but with unusual features such as brushes on pivots rather than a slide. The multiple sets of gears are packed in aged and phenolic-smelling grease, and have unusual features such as stub-form teeth for high torque at low durations. There is even an entirely separate gear train for the hex drive provided so that crews could keep the bombers rolling even when the power was out.
He leaves us with the tantalising information that there is a project awaiting this device, but doesn’t tell us what that might be. We hope we’ll get to see it, whatever it is. Meanwhile it’s great to see that this kind of item can still be found from military surplus suppliers, where this is being written they have degenerated into little more than stockists of camouflage-printed camping gear. Our colleague [Brandon Dunson] lamented in 2015 on the slow decline of the electronic surplus business in his location.
Big companies spend small fortunes on making sure their computers stay running and that they can be repaired quickly in an emergency. You wouldn’t expect an emergency repair on an Amiga 2000, though. [RETR-O-MAT] bought an Amiga 2000 that did boot, but was known to have a leaky battery on the motherboard. He wanted to rush to replace the battery before the leakage caused serious damage. You can see all this in the video below.
The computer looked lightly used over its 32-year lifespan, even when the case came off. The battery corrosion was evident, though. Even the bolt holding down the motherboard was clearly corroded from the leaking battery, causing it to be very difficult to remove.
The battery leakage also made unsoldering the battery a challenge. Several chips and sockets — including the CPU — were affected, so they had to come out. You can see a nice demonstration of the “old screwdriver trick” which might be eye-opening if you’ve only worked with SMD chips.
Even if you don’t care much about the Amiga 2000, it is interesting to see inside an old computer like this and note the differences — and similarities — to modern designs. The video is as much a tear down as it is a repair story. It also might be useful if you ever face having to tear out a leaky battery on any piece of gear. Continue reading “Amiga 2000 Emergency Repair”→
[Syonyk] has been acquiring some large load banks to test power supplies and battery packs. These devices consist of a big current sink, a measurement device, and a fan. He picked up two similar-looking boards from the usual Chinese sources, both rated for 150W, both for about $30. Upon closer examination, though, he found that one was really a bargain and the other was likely to blow up.
The loads are rated for 60V and as you can see from the photos, appear virtually identical at a glance. They offer a configurable cut-off voltage and even use 4-wire measurement to avoid problems with voltage drop through the power cables.
I immediately felt uncomfortable when I realized this thing is called the “Breo iPalm520 Acupressure Hand Massager”. You’re supposed to stick your hand into it, and through unknown machinations it performs some kind of pressure massage complete with heating action. It’s like one of those pain boxes from Dune. It’s all the more disturbing when you realize the red button on the thing is an emergency release. That’s right, once your hand is in this contraption you can’t take it out until the thing has had its way with you or you tap out.
At least once a week I try to get to the local thrift store to look for interesting things. I’d like to be more specific than “interesting things”, but truth be told, I never really know what I’m looking for until I see it. Sure there’s the normal consumer electronics kind of stuff, but I’ve also found some very nice laboratory equipment, computer parts, software, technical books, etc. You just have to go regularly and keep an eye out for the occasional needle amongst the hay.
I want you to know, Dear Readers, that I did briefly summon the courage to put my hand into this thing and turn it on. Now I am not what one might call an overly brave man, and perhaps that might explain my personal experience. But when it started to hum and heat up, constricting around my hand to the point I couldn’t move my fingers, I screamed like a child and mashed the emergency button as if I was a pilot trying to eject from a mortally wounded aircraft. As far as Frank Herbert is concerned, I’m no human at all.
In an effort to better understand this torture device, lets open it up and see what lurks beneath that futuristic exterior.
[IMSAI Guy] tore apart a device with a wireless network card and decided to investigate what was under the metal can. You can see the video of his examination below. Overall, it was fairly unremarkable, but one thing that was interesting was its use of an antenna on the PCB that uses a fractal design.
You probably know fractals are “self-similar” in that they are patterns made of smaller identical patterns. The old joke is that the B. in Benoit B. Mandelbrot (the guy who coined the term fractal) stands for Benoit B. Mandelbrot. You can think of it as akin to recursion in software. Antennas made with fractal patterns have some unusual and useful properties.