Anything with a laser has undeniable hacker appeal, even if the laser’s task is as pedestrian as sending data over a fiber optic cable. [Shahriar] from [The Signal Path] must agree, and you can watch as he tears down and investigates a fiber optic link made from old HP equipment in the video below.
He starts with an investigation of the block diagram of the transmitter. In the transmitter, the indium gallium arsenide phosphide laser diode emits light with a 1310-nanometer wavelength. Thermal characteristics in the transmitter are important, so there is thermal control circuitry. He notes that this system only works using amplitude modulation; phase modulation would require more expensive parts. Then it’s time to look at the receiver’s block diagram. Some optics direct the light signal to a PIN diode, which receives the signal and interfaces with biasing and amplifying circuitry.
The eccentric shaft and rotor of the Mazda 12A rotary engine. (Credit: Baked Beans Garage, YouTube)
In theory, Wankel-style rotary internal combustion engines have many advantages: they ditch the cumbersome crankcase and piston design, replacing it with a simple, single-chamber design and a thick, plectrum-shaped chunk of metal that spins around inside that chamber to create virtual combustion chambers. This saves weight and maximizes performance-to-weight. Unfortunately, these types of engines are also known for burning a lot of oil and endless seal troubles, especially with early rotary Mazda engines that easily died.
Yet even 1980 versions were not without issues, a case in point is the Mazda 1st gen RX7 with a 12A rotary engine that the [Baked Beans Garage] over at YouTube got their paws on. Starting with unsuccessful attempts to make the car start, the next step was to roll the car into the morgue garage for a full teardown of the clearly deceased engine.
About 35 minutes into the video, we get to the teardown of the engine, with its parts contrasted with those of a newer revision rotary engines alongside illustrations of their functioning, making it as much an autopsy as a detailed introduction to these rotary engines. Technically, they also aren’t the original DKM-style Wankel engines, but a KKM-style engine, as designed by [Hanns-Dieter Paschke]. [Wankel] didn’t like the eccentric KKM design, as he thought it’d put too much stress on the apex seals, but ultimately the more economical KKM design was further developed.
During the autopsy of the 12A revision Mazda engine, it becomes clear that it was likely overheating that killed the engine over the course of years of abuse, along with ‘chatter’ marks of the apex seals destroying the inner chrome coating. This would have compromised compression and with it any chance of the engine running, not unlike a piston engine with badly scored cylinder walls after ingesting some metal chunks.
While the Mazda 12B and subsequent designs addressed many of the issues with the early rotary engines, its use was limited to some sports models, ending in 2012 with the RX-8. The currently produced Mazda MX-30 does use a rotary engine again in its plug-in hybrid version, but it’s only as a range extender engine that drives a generator. Looking at the internals of those Mazda rotary engines, it’s easy to see how complex they are to keep running, but you cannot help but feel a little bit of sadness that these small-but-powerful engines didn’t make much more of a splash.
[JohnAudioTech] noticed there was no bass on the TV at his parents’ house. That led to the discovery of a blown fuse and a corresponding repair. When he opened it up, he could smell that something had gone on in the amplifier. You can follow the repair in the video below.
His first theory was that some glue became conductive and shorted the power rails. We were skeptical, to be honest. When he fed power to it through a current limiter, he could hear a sizzling noise and even see a little glowing from the hot component.
Disassembly ensued. Removing the suspect components showed some seriously burned components and some charring under a switching transistor. The capacitors looked much worse for wear, and the PCB needed some wires to jumper burned conductors.
At the end, there was thumping, so it seems the surgery was a success. However, testing blew a fuse again, which made us nervous. Still, seems to work if you don’t drive it too hard.
We always enjoy watching a teardown, and if there’s a repair too, that’s even better.
The geometric waveguide glass of the Meta Ray-Ban Display glasses. (Credit iFixit)
Recently the avid teardown folk over at iFixit got their paws on Meta’s Ray-Ban Display glasses, for a literal in-depth look at these smart glasses. Along the way they came across the fascinating geometric waveguide technology that makes the floating display feature work so well. There’s also an accompanying video of the entire teardown, for those who enjoy watching a metal box cutter get jammed into plastic.
Overall, these smart glasses can be considered to be somewhat repairable, as you can pry the arms open with a bit of heat. Inside you’ll find the 960 mWh battery and a handful of PCBs, but finding spare parts for anything beyond perhaps the battery will be a challenge. The front part of the glasses contain the antennae and the special lens on the right side that works with the liquid crystal on silicon (LCoS) projector to reflect the image back to your eye.
While LCoS has been used for many years already, including Google Glass, it’s the glass that provides the biggest technological advancement. Instead of the typical diffractive waveguide it uses a geometric reflective waveguide made by Schott, with the technology developed by Lumus for use in augmented reality (AR) applications. This is supposed to offer better optical efficiency, as well as less light leakage into or out of the waveguide.
Although definitely impressive technology, the overall repairability score of these smart glasses is pretty low, and you have to contest with both looking incredibly dorky and some people considering you to be a bit of a glasshole.
It takes quite a bit of effort to get a 0 out of 10 repairability score from iFixit, but in-ears like Apple’s AirPods are well on course for a clean streak there, with the AirPod Pro 3 making an abysmal showing in their vitriolic teardown video alongside their summary article. The conclusion is that while they are really well-engineered devices with a good feature set, the moment the battery wears out it is effectively e-waste. The inability to open them without causing at least some level of cosmetic damage is bad, and that’s before trying to glue the device back together. Never mind effecting any repairs beyond this.
Worse is that this glued-together nightmare continues with the charging case. Although you’d expect to be able to disassemble this case for a battery swap, it too is glued shut to the point where a non-destructive entry is basically impossible. As iFixit rightfully points out, there are plenty of examples of how to do it better, like the Fairbuds in-ears. We have seen other in-ears in the past that can have some maintenance performed without having to resort to violence, which makes Apple’s decisions here seem to be on purpose.
Although in the comments to the video there seem to be plenty of happy AirPod users for whom the expected 2-3 year lifespan is no objection, it’s clear that the AirPods are still getting zero love from the iFixit folk.
The counter wheel and white worm gear inside the counter. (Credit: Anthony Francis-Jones, YouTube)
Recently [Anthony Francis-Jones] decided to take a closer look at the inhaler that his son got prescribed for some mild breathing issues, specifically to teardown the mechanical counter on it. Commonly used with COPD conditions as well as asthma, these inhalers are designed to provide the person using it with an exact dose of medication that helps to relax the muscles of the airways. Considering the somewhat crucial nature of this in the case of extreme forms of COPD, the mechanical counter that existed on older versions of these inhalers is very helpful to know how many doses you have left.
Disassembling the inhaler is very easy, with the counter section easily extracted and further disassembled. The mechanism is both ingenious and simple, featuring the counter wheel that’s driven by a worm gear, itself engaged by a ratcheting mechanism that’s progressed every time the cylinder with the medication is pushed down against a metal spring.
After the counter wheel hits the 0 mark, a plastic tab prevents it from spinning any further, so that you know for certain that the medication has run out. In the video [Anthony] speculates that the newer, counter-less inhalers that they got with the latest prescription can perhaps be harvested for their medication cylinder to refill the old inhaler, followed by resetting the mechanical counter. Of course, this should absolutely not be taken as medical advice.
The 600W is not the output rating, despite all appearances. (Credit: Denki Otaku, YouTube)
We have seen many scam USB chargers appear over the years, with a number of them being enthusiastically ripped apart and analyzed by fairly tame electrical engineers. Often these are obvious scams with clear fire risks, massively overstated claims and/or electrocution hazards. This is where the “600W” multi-port USB charger from AliExpress that [Denki Otaku] looked at is so fascinating, as despite only outputting 170 Watt before cutting out, it’s technically not lying in its marketing and generally well-engineered.
The trick being that the “600W” is effectively just the model name, even if you could mistake it for the summed up output power as listed on the ports. The claimed GaN components are also there, with all three claimed parts counted and present in the main power conversion stages, along with the expected efficiency gains.
While testing USB-PD voltages and current on the USB-C ports, the supported USB-PD EPR wattage and voltages significantly reduce when you start using ports, indicating that they’re clearly being shared, but this is all listed on the product page.
The main PCB of the unit generates the 28 VDC that’s also the maximum voltage that the USB-C ports can output, with lower voltages generated as needed. On the PCB with the USB ports we find the step-down converters for this, as well as the USB-PD and other USB charging control chips. With only a limited number of these to go around, the controller will change the current per port dynamically as the load increases, as you would expect.
Considering that this particular charger can be bought for around $30, is up-front about the limitations and uses GaN, while a genuine 300 Watt charger from a brand like Anker goes for $140+, it leads one to question the expectations of the buyer more than anything. While not an outright scam like those outrageous $20 ‘2 TB’ SSDs, it does seem to prey on people who have little technical understanding of what crazy amounts of cash you’d have to spend for a genuine 600 Watt GaN multi-port USB charger, never mind how big such a unit would be.
