Teardown

531 Articles

Educational Radio, Educates

June 22, 2020 by 11 Comments

Analyzing and troubleshooting a modern AM/FM radio, digital radio, or TV can be a pretty daunting task. However, a common AM radio is easy to understand, experiment with, and repair. Learning about that will help you understand more complex circuits later. That’s the idea behind the Elenco AM radio which is built on a wide-open PCB with markings for all the important sections. [The Offset Volt] uses one of these to explain how a receiver works, especially how a diode detects the signal and how the automatic gain control works.

Between a series of diagrams and live scope demonstrations, you can see the effects of capacitance in the receiver along with other circuit effects.

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Teardown: Wonder Bible

June 22, 2020 by 91 Comments

Even the most secular among us can understand why somebody would want to have a digital version of the Bible. If you’re the sort of person who takes solace in reading from the “Good Book”, you’d probably like the ability to do so wherever and whenever possible. But as it so happens, a large number of people who would be interested in a more conveniently transportable version of the Bible may not have the technological wherewithal to operate a Kindle and download a copy.

Which is precisely the idea behind the Wonder Bible, a pocket-sized electronic device that allows the user to listen to the Bible read aloud at the press of a button. Its conservative design, high-contrast LED display, and large buttons makes it easy to operate even by users with limited eyesight or dexterity.

The commercial for the Wonder Bible shows people all of all ages using the device, but it’s not very difficult to read between the lines and see who the gadget is really aimed for. We catch a glimpse of a young businessman tucking a Wonder Bible into the center console of his expensive sports car, but in reality, the scenes of a retiree sitting pensively in her living room are far closer to the mark.

In truth, the functionality of the Wonder Bible could easily be replicated with a smartphone application. It would arguably even be an improvement by most standards. But not everyone is willing or able to go that route, which creates a market for an affordable stand-alone device. Is that market large enough to put a lot of expense and engineering time into the product? Let’s crack open one of these holy rolling personal companions and find out.

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Just How Do Aircraft Transponders Work Anyway?

June 22, 2020 by 32 Comments

Most of us will have a hazy idea of how radar works to detect aircraft by listening for reflected radio waves. And we’ll probably also know that while radar can detect aircraft, it’s not the most efficient or useful tool in the hands of an air traffic controller. Aircraft carry transponders so that those on the ground can have a clearer picture of the skies, as each one reports its identity, altitude, and position. [Yeo Kheng Meng] was lucky enough to secure a non-functioning aircraft transponder and do a teardown, and his write-up makes for interesting reading as he explains their operation before diving into the hardware.

The 1978 and 1979 date codes on the various integrated circuits and transistors identify it as having been made in 1979, so not having a CPU is not entirely unsurprising given its age. Instead this is a straightforward device that responds to pulse lengths of different timings with sequential bursts of data.

[Yeo Kheng] is mystified by the RF strip and associated components, which look to us like a typical crystal oscillator and frequency multiplier strip from that era, along with some screened boxes that probably contain cavity filters and given that there is also a high voltage power supply present, a tube RF power amplifier. GHz-capable semiconductors were quite exotic in the 1970s, while high-frequency tubes had by then a long history.

It’s evident that the tech behind aircraft transponders has moved on since this unit was built, but one thing’s certain. Hackers in 1978 would have had to go to a lot of work to listen to them and interpret the results, while here in the 21st century it’s something we do routinely.

Repairing A Workhorse Bench Meter

June 18, 2020 by 23 Comments

In today’s market, and expensive high-precision bench meter will have a host of features: graphs, alarms, averaging, and more. It will probably even use an operating system. However, old meters can still get the job done at a price that you can actually afford. A case in point is the Fluke 8842A, solid meters with 5.5 digits of resolution and the ability to do two or four wire resistance measurements.  They are built like tanks and are surprisingly affordable, especially if you consider what they went for when new. [Illya Tsemenko] recently updated a log about repairing such a meter, and there is a lot of good information about them if you own one or are thinking about one.

The biggest problem with repairing these meters is that there are several custom parts including the display that are essentially unavailable. For that reason, [Illya] took a meter with a broken display and used it to source parts for another meter.

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Teardown: The Writer Word Processor

June 9, 2020 by 61 Comments

For modern students, the spiral notebook has given way to the laptop and the pocket calculator has been supplanted by the smart phone. We’re not just talking about high school and college, either. Today, the education of even grade school children is intrinsically linked with technology. While some might question the wisdom of moving away from the pencil and pad at such a young age, there’s little question that all the kids stuck at home right now due to COVID-19 would have had a much harder time transitioning to remote learning otherwise.

But that certainly wasn’t the case when Advanced Keyboard Technologies released the Writer in 2003. Back then, five years before the first netbooks hit the market, you’d be hard pressed to find a laptop cheap enough to give to a grade school student. In comparison, these small electronic word processors could be purchased for as little as $150. Not only was the initial price low, but the maintenance costs were almost negligible. They ran for hundreds of hours on a standard AA batteries, and didn’t require schools to have any IT staff to manage them. Sure they couldn’t get on the Internet or even run any software, but they would give students a chance to hone their keyboarding skills. Continue reading “Teardown: The Writer Word Processor” →

Fighter Jet’s Gyro Stays Upright Before It Self-Destructs

June 3, 2020 by 18 Comments

Aviation instruments are highly interesting pieces of engineering, and it is quite satisfying to watch the often over-engineered mechanisms behind them. If you are into that sort of thing it is worthwhile to check out [Erik Baigar]’s video where he explains the working principle of the attitude indicator from a Tornado jet.

The attitude indicator or artificial horizon of an airplane is one of the most important instruments, especially during poor sight. The ADI42-124 used in the Tornado jet is completely standalone and only needs a DC power supply which is why [Erik Baigar] can show it off while standing on his balcony. At the heart of this instrument is a gyroscope which consists of a spinning disc attached to a gimbal mount. Due to the conservation of angular momentum, the spin axis will always keep its orientation when the instrument is rotated. However, mechanical gyroscopes tend to drift over time and therefore include a mechanism to keep the spin axis upright with respect to the direction of gravity. The ADI42-124 uses an entirely mechanical mechanism for this based on free swiveling weights. Forget everything we said earlier about overengineering as [Erik Baigar] also uncovers a fatal design flaw which leads to the instrument’s self-destruction as shown in the picture here. Unfortunately, this will render most of the units you can buy on eBay useless.

Be sure to check out [Erik Baigar]’s webpage which is nerd paradise for vintage computer and avionics fans or watch another gyroscope teardown.

Video after the break.

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Teardown: Nabaztag

May 26, 2020 by 27 Comments

In 2020 there is nothing novel or exciting about an online device. Even the most capable models are designed to be unobrusive pucks and smart speakers; their function lies in what they do rather than in how they look. In 2005, an Internet connected device was a rare curiosity, a daring symbol of a new age: the “Internet of Things”!

Our fridges were going to suggest recipes based upon their contents, and very few people had yet thought of the implications of an always-on connected appliance harvesting your data on behalf of a global corporation. Into this arena stepped the Nabaztag (from the Armenian for “rabbit”), an information appliance in the form of a stylised French plastic rabbit that could deliver voice alerts, and indicate status alerts by flashing lights and moving its ears.

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