If you’ve ever seen the cockpit of an airplane, you’ve probably noticed the round ball that shows your attitude, and if you are like us, you’ve wondered exactly how the Attitude Direction Indicator (ADI) works. Well, [msylvain59] is tearing one apart in the video below, so you can satisfy your curiosity in less than 30 minutes.
Like most things on an airplane, it is built solidly and compactly. With the lid open, it reminded us of a tiny CRT oscilloscope, except the CRT is really the ball display. It also has gears, which is something we don’t expect to see in a scope.
[Thomas Scherrer] likes to tear down old test equipment, and often, we remember the devices he opens up or — at least — we’ve heard of them. However, this time, he’s got a Hung Chang HC-F100 multifunction counter, which is a vintage 1986 instrument that can reach 100 MHz.
Inside, the product is clearly a child of its time period. There’s a transformer for the linear supply, through-hole components, and an Intersil frequency counter on a chip. Everything is easy to get to and large enough to see.
If you ever encounter a British engineer of a certain age, the chances are that even if they use a modern DMM they’ll have a big boxy multimeter in their possession. This is the famous Avo 8, in its day the analogue multimeter to have. Of course it wasn’t the only AVO product, and [Thomas Scherrer OZ2CPU] is here with another black box sporting an AVO logo. This one’s an AC bridge, one of a series of models manufactured from the 1930s through to the late 1940s, and he treats us to a teardown and restoration of it.
Most readers will probably be familiar with the operation of a DC Wheatstone Bridge in which two resistances can be compared, and an AC bridge is the same idea but using an AC source. A component under test is attached to one set of terminals while one with a known value is put on the other, and the device can then be adjusted for a minimum reading on its meter to achieve a state of balance. The amount by which it is adjusted can then be used as a measure of the difference between the two parts, and thus the value of an unknown part can be deduced.
In the case of this AVO the AC is the 50Hz (remembering that this is a British instrument) mains frequency, and the reading from the bridge is taken via a single tube amplifier to a rectifier circuit and the meter. Inside it’s a treasure trove of vintage parts with an electrolytic capacitor that looks as though it might not be original, with a selenium rectifier and a copper oxide signal diode in particular catching our eye. This last part is responsible for some reading anomalies, but after cleaning and lubricating all the switches and bringing up the voltage gently, he’s rewarded with a working bridge. You can see the whole story in the video below the break.
[Poking Technology] doesn’t think much of his new smartwatch. It is, by his admission, the cheapest possible smartwatch, coming in at about $3. It has very few useful features but he has figured out how to port MicroPython to it, so for a wrist-mounted development board with BLE, it might be useful. You can check it out in the video below.
The first step is a teardown, which reveals surprisingly little on the inside. There’s a tiny battery, a few connections, a display, and a tiny CPU board. There are, luckily, a few test pads that let you get into the CPU. What do you get? A 24 MHz Telink CPU with 512k of flash and 16k of RAM, along with all the other hardware.
For old-timers, CRTs — cathode ray tubes — were fixtures as kids sat in front of TVs watching everything from Howdy Doody to Star Trek. But there’s at least one generation that thinks TVs and computer monitors are flat. If that describes you, you might enjoy [The 8-Bit Guy’s] coverage of how CRTs work in the video below.
CRTs were heavy, took high voltage, and had a dangerous vacuum inside, so we really don’t miss them. The phosphor on the screen had a tendency to “burn in” if you showed the same image over and over. We don’t miss that either.
[Thomas] found an interesting probable millivoltmeter with some Beckman displays. Like many instruments from that time period, this one had a lot of tobacco smoke residue inside. The display unit inside had a sticker that not only showed the company that made it, but also had their Telex number on it, another sign of the times. You can see the device in the video below.
The unit looked like a one-off made by a hobbyist or a technician but the case looked suspiciously like old Bang and Olfusen equipment. Someone in the video comments mentions it was built for the service department.
The Surface Arc is a designed-for-travel mouse that carries flat, but curves into shape for use. It even turns on when it’s bent and shuts itself off when it’s flat. The device isn’t particularly new, but [Mr Teardown] was a bit surprised at the lack of details about what’s inside so tears it down in a video to reveal just how the mechanism works.
The mechanism somewhat resembles a beaver’s tail, and locks into place thanks to a magnetic connector at the base that holds the device’s shape.
The snap-action of the bending is accomplished with the help of a magnetic connection near the bottom end of the mouse’s “tail”, locking it into place when flexed. Interestingly, the on and off functionality does not involve magnets at all. Power control is accomplished by a little tab that physically actuates a microswitch.
There are a few interesting design bits that we weren’t expecting. For example, there is no mechanical scroll wheel. The mouse delivers similar functionality with touch sensors and a haptic feedback motor to simulate the feel and operation of a mechanical scroll wheel.
[Mr Teardown] finds the design elegant and effective, but we can’t help but notice it also seems perhaps not as optimized as it could be. There are over 70 components in all, including 23 screws (eight different kinds!), and it took [Mr Teardown] the better part of 45 minutes to re-assemble it. You can watch the entire teardown in the video embedded just under the page break; it’s a neat piece of hardware for sure.
If you’re in the mood for another mouse teardown, we have a treat for you: an ancient optical mouse from the 80s that required a special surface to work.
