A Stereo Tube Amp For Less Than $5

July 30, 2018 by Ben James 21 Comments

Many of us have aspirations of owning a tube amp. Regardless of the debate on whether or not tube audio is nicer to listen to, or even if you can hear the difference at all, they’re gorgeous to look at. However, the price of buying one to find out if it floats your boat is often too high to justify a purchase.

[The Post Apocalyptic Inventor] has built a stereo tube amplifier in the style of the Fallout video games. The idea came when he realised that the TK 125 tape recorder manufactured by Grundig was still using tube audio in the late 60s. What’s more, they frequently sell on eBay for 1-10€ in Germany. [TPAI] was able to salvage the main power amplifier from one of these models, and restore it so that it could be re-purposed and see use once more.

The teardown of the original cassette recorder yields some interesting parts. Firstly, an integrated motor transformer — an induction motor whose stator acts as the magnetic core of the transformer responsible for the tube electronics. There’s also an integrated capacitor which contains three separate electrolytics. The video after the break is well worth a watch (we always find [TPAI]’s videos entertaining).

A new chassis is created out of a steel base plate and aluminium angle, and some neat frames for the motor transformers are made from scrap copper wire bent and soldered together. It looks great, though there’s always the option to use a cake tin instead.

If you’re interested in the design of tube amps, we’ve covered heaps of cool builds: from this low-voltage design to this tiny guitar amp, or even ones using tubes which are flat.

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Milspec Teardown: C-1282 Chaff Controller

July 24, 2018 by Tom Nardi 37 Comments

A B-52 bomber is approaching its primary target: rail yards in the Beloostrov district of Leningrad. Intel reports the area is likely defended by S-25 Berkut and S-75 Dvinia surface to air missiles (SAMs), but this close to the target the gigantic bomber can’t afford to make the evasive maneuvers, known as combat turns, which would help shake off enemy air defenses. From his position behind the co-pilot, the electronic warfare officer (EWO) reaches over and sets the C-1282 for continuous chaff ejection. Hundreds of thin metallic strips are jettisoned from the B-52, confusing tracking radar and allowing the bomber and her crew to slip through the Soviet air defenses and drop 50,000 lbs of ordnance directly onto the target.

Luckily for all of us, this event never actually occurred. But it was a possibility that the United States and Soviet Union had prepared for extensively. Both sides developed ever more capable weapons, and for each new weapon, a new countermeasure was invariably created. The C-1282 is a component of one such countermeasure, a device that allowed the B-52’s EWO to configure and monitor the bomber’s automatic chaff dispenser. With the C-1282 handling the anti-radar countermeasures, the bomber’s crew could focus their attention on completing their mission.

Of course, as is the case with technology (military or otherwise), the C-1282 was eventually phased out for something new. These old units, now largely worthless, were destroyed or sentenced to a lifetime collecting dust on a storeroom shelf. But through the magic of the Internet, one of these devices is now ready to be laid bare for your viewing pleasure. Dust off your Joseph McCarthy Junior Detective badge and come along as we take a look at a state of the art piece of Anti-Ruskie technology, circa 1960.

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What’s Inside A Scientology E-Meter?

July 19, 2018 by Brian Benchoff 146 Comments

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.

Check out the video below of the entire teardown.

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Bomb Hoist Teardown Shows Cold-War-Era Big Iron

July 17, 2018 by Jenny List 10 Comments

Buying surplus equipment lends a frisson of excitement as you eagerly await the package or crate containing your purchase. Did you buy a hidden treasure, or has some shyster succeeded in unloading a pile of garbage onto you, their mark? [Professor Churls] shelled out $49.99 for a military surplus bomb hoist which definitely falls into the former category. His teardown reveals it to be a beautifully over-engineered piece of Cold-War-era American hardware.

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.

Teardown Of Sonos And Amazon Smart Speakers Reveals Interesting Engineering Details

July 12, 2018 by Richard Baguley 24 Comments

Taking things apart is always fun, and this What Cracking Open a Sonos One Tells Us About the Sonos IPO”>excellent writeup of a teardown of a Sonos and Amazon smart speaker by [Ben Einstein] shows what you can learn. [Ben] is a Venture Capitalist and engineer, so much of his write up focuses on what the devices say about how the company spends money. There are plenty of things to learn for hackers, though: he details how the Sonos One uses a PCI daughterboard for wireless communications, while the Amazon Echo has a programmable radio on the main board.

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Amiga 2000 Emergency Repair

July 8, 2018 by Al Williams 20 Comments

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” →

Load Bank Teardowns Show Danger

July 2, 2018 by Al Williams 16 Comments

[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.

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