Reviewing A Very Dodgy BSK-602 Adjustable Power Supply

There’s no shortage of cheap & cheerful power supplies which you can obtain from a range of online retailers, but with no listed certification worth anything on them calling them ‘dodgy’ is more of a compliment. On the [DiodeGoneWild] YouTube channel an adjustable power supply by the model name BSK-602 is tested and torn down to see exactly what less than $5 off sites like Alibaba will get you.

Perhaps unsurprisingly, voltage regulation is very unstable with massive drifting when left to heat up for a few hours, even though it does hit the 3 V to 24 V DC and 3 A output that it’s optimistically rated for. After popping open the adapter, a very basic switching mode power supply is revealed with an abysmal component selection and zero regard for safety or primary and secondary side isolation. With the case open, the thermal camera reveals that the secondary side heats up to well over 150 °C, explaining why the case was deforming and the sticker peeling off after a few hours of testing.

The circuit itself is based around a (possibly legit) UC3843RN 500 kHz current mode PWM controller, with the full schematic explained in the video. Highlights include the lack of inrush protection, no EMI filtering, a terrible & temperature-dependent voltage reference, not to mention poor component selection and implementation. Basically it’s an excellent SMPS if you want to blast EMI, fry connected electronics and conceivably burn down your home.

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Repairing An Old Heathkit ‘Scope

With so many cheap oscilloscopes out there, the market for old units isn’t what it used to be. But if you have a really old scope, like the Heathkit O-10 that [Ken] found in his basement, there is vintage cred to having one. [Ken’s] didn’t work, so a repair session ensued. You can see the results in the video below.

You can tell this is in an old scope — probably from the mid 1950s — because of its round tube with no graticle. Like many period scopes, the test probe input was just 5-way binding posts. The O-10 was the first Heathkit “O-series” scope that used printed circuit boards.

The device looked pretty good inside, except for a few dents. Of course, the box has tubes in it, so every power up test involves waiting for the tubes to warm up. [Ken] was very excited when he finally got a single green dot on the screen. That did, however, require a new CRT.

It wasn’t long after that he was able to put a waveform in and the scope did a good job of reproducing it. The unit would look good in an old movie, but might not be the most practical bench instrument these days.

These Heathkit scopes and their cousins were very popular in their day. The $70 price tag sounds cheap, but in the mid-1950s, that was about a month’s rent in a four-room house. While primitive by today’s standards, scopes had come a long way in 9 or 10 years.

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Understanding The T12 Style Soldering Iron Tip

Soldering irons and their tips come in a wide range of formats and styles, with the (originally Hakko) T12 being one of the more interesting offerings. This is because of how it integrates not only the tip and heating element, but also a thermocouple and everything else in a self-contained package. In a recent video [Big Clive] decided to not only poke at one of these T12 tips, but also do a teardown.

These elements have three bands, corresponding to the power supply along with a contact for the built-in thermocouple. After a quick trip to the Vise of Knowledge, [Clive] allows us a glimpse at the mangled remnants of a T12, which provides a pretty good overview of how these tips are put together.

Perhaps unsurprisingly, most of the length is a hollow tube through which the wires from the three contacts run. These power the ceramic heating element, as well as provide the soldering iron handle access to the thermocouple that’s placed near the actual tip.

With a simple diagram [Clive] explains how these T12 elements are then used to regulate the temperature, which isn’t too distinct from the average soldering iron with ceramic heating element, but it’s still nice to have it all integrated rather than having to try to carefully not damage the ceramic heater while swapping tips with the average soldering iron.

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Stepper Motor Operating Principle And Microstepping Explained

The [Denki Otaku] YouTube channel took a look recently at some stepper motors, or ‘stepping motors’ as they’re called in Japanese. Using a 2-phase stepper motor as an example, the stepper motor is taken apart and its components explained. Next a primer on the types and the ways of driving stepper motors is given, providing a decent overview of the basics at the hand of practical examples.

As great as theoretical explanations are, there’s a lot of value in watching the internals of a stepper motor move when its coils are activated in order. Also demonstrated are PWM-controlled stepper motor drivers before diving into the peculiarities of microstepping, whereby the driving of the coils is done such that the stator moves in the smallest possible increments, often through flux levels in these coils. This allows for significantly finer positioning of the output shaft than with wave stepping and similar methods that are highly dependent on the number of phases and coils.

As demonstrated in the video, another major benefit of microstepping is that it creates much smoother movement while moving, but also noted is that servo motors are often what you want instead. This is a topic which we addressed in our recent article on the workings of stepper motors, with particular focus on the 4-phase 28BYJ-48 stepper motor and the disadvantages of steppers versus servos.

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Inside A Vintage Oven Controlled Crystal Oscillator

Crystal oscillators are incredibly useful components, but they come with one little snag: their oscillation is temperature-dependent. For many applications the relatively small deviation is not a problem, but especially for precision instruments this is a deal breaker. Enter the oven controlled crystal oscillator, or OCXO. These do basically what it says on the tin, but what’s inside them? [Kerry Wong] took apart a vintage Toyocom TCO-627VC 10 MHz OCXO, revealing a lot more complexity than one might assume.

Inside the insulated enclosure there is of course the crystal oscillator itself, which has a heating coil wrapped around it. Of note is that other OCXOs that [Kerry] took apart had more insulation, as well as other ways of providing the thermal energy. In this particular unit a thermistor is attached to the crystal’s metal case to measure its temperature and provide feedback to the heating circuit. The ICs on the PCB are hard to identify due to the conformal coating, but at least one appears to be a 74LS00, alongside a 78L05 voltage regulator which reduces the 12V input voltage.

As an older OCXO it probably is a lot chunkier than newer units, but the basic principle remains the same, with a heating loop that ensures that the crystal inside the unit remains at the same temperature.

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A 1962 Test Gear Teardown

Although it sounds like some Star Trek McGuffin, a Q-Meter is a piece of test gear that measures the Q factor of a tuned circuit. [Thomas] got a Boonton meter from 1962 that wasn’t in very good shape, but it was a fun teardown, as you can see in the video below. The meter had signs of a prior modification or repair, but still a nice peek into some vintage gear.

The meter could measure up to 260 MHz (or megacycles in 1962 parlance) and had some unusual features, including an oddly wired AC transformer and a “voltage stabilizer” to ensure a constant AC voltage at the input. We have to admit, we miss the days when our test equipment had gears inside. Then again, we don’t miss the tubes and the high-voltage stuff. Because of the high frequency, the unit even has an oddball acorn tube that you rarely see.

You may notice the meter has a mirror in a strip on the face. This is a common feature of high-precision analog meter movements. The idea is that you move your head until the needle hides its own reflection in the mirror to avoid parallax errors in your reading.

This isn’t the first Q meter we’ve seen; in fact, one was pretty similar but a bit older. While you can get a lot of new gear cheap these days, there’s still something to be said for vintage test equipment.

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A dismantled drill on a cluttered workbench

Going Brushless: Salvaging A Dead Drill

Let’s face it—seeing a good tool go to waste is heartbreaking. So when his cordless drill’s motor gave up after some unfortunate exposure to the elements, [Chaz] wasn’t about to bin it. Instead, he embarked on a brave journey to breathe new life into the machine by swapping its dying brushed motor for a sleek brushless upgrade.

Things got real as [Chaz] dismantled the drill, comparing its guts to a salvaged portable bandsaw motor. What looked like an easy swap soon became a true hacker’s challenge: incompatible gear systems, dodgy windings, and warped laminations. Not discouraged by that, he dreamed up a hybrid solution: 3D-printing a custom adapter to make the brushless motor fit snugly into the existing housing.

The trickiest part was designing a speed control mechanism for the brushless motor—an impressively solved puzzle. After some serious elbow grease and ingenuity, the franken-drill emerged better than ever. We’ve seen some brushless hacks before, and this is worth adding to the list. A great tool hack and successful way to save an old beloved drill. Go ahead and check out the video below!

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