We’ve seen our share of light-up jewelry over the years, but for some reason — probably power — it’s almost always earrings or necklaces. So when we saw [ROBO HUB]’s LED ring, we had to check it out. It involves a bit of behind-the-scenes action in the form of a battery holder that you palm, but the end effect is quite cool.
Essentially, this is a 3D printed ring with SMD LEDs painstakingly soldered together in parallel along a pair of thin copper wires. The ring itself is in two parts: a base, and a cover to diffuse and protect the LEDs. A pair of wires run out from the ring and connect to a printed coin cell holder.
Apple Macintosh computers of the 1990s came with a system ROM containing an Open Firmware implementation and the Mac Toolbox required to start the operating system. In many cases this was on a SIMM-like daughter board, and it would have been a true ROM that was unable to be reprogrammed. This is not the end of the story though, and [Doug Brown] set out on the trail of a Flash-based ROM module allowing the firmware on these machines to be updated.
The trail was warm thanks to an Apple developer utility found on a secondhand Mac prototype, allowing ROM flashing. A little disassembly allowed a list of valid IDs to be made, and this info coupled with a bit of reverse engineering from online photos of a real Apple Flash ROM from the ’90s allowed a new board to be created with four Am28F020 chips. He can now flash at will, with such oddities as running ROMs from different machines with the “wrong” startup chime. It’s an interesting little piece of 1990s Mac trivia, settled.
In a world increasingly reliant on technology, a pressing question arises: can our dependence on gadgets, particularly mobile phones, be affecting our health in unexpected ways? A growing body of research is now pointing towards a startling trend – declining sperm quality in the human population – with mobile phones emerging as a potential culprit.
Recent studies have been sounding the alarm over a noticeable decline in sperm counts and quality across the globe. This decline isn’t just about quantity; it’s about the vitality, motility, and overall health of sperm cells. The implications of this trend are profound, affecting fertility rates and possibly even the long-term viability of populations. The situation is murky and complicated, but new studies suggest that cellular phones could have a role to play.
In hindsight, it seems obvious to this American: attach strings to the tops of bowling pins so they can be yanked upward into holes that settle down the action so that the pins can be reset. In fact, European bowling “houses” have used string pinsetters for decades, instead of lumbering machinery that needs regular maintenance and costs several thousand dollars a month to maintain.
Many readers will have at some time or another built their own lithium-ion battery packs, whether they are using tiny cells or the huge ones found in automotive packs. A popular choice it to salvage ubiquitous 18650 cylindrical cells, as [limpkin] has with this 48 volt pack. It’s based around an off-the-shelf kit aimed at the e-bike market, but it’s much more than a simple assembly job.
Faced with a hundred salvaged cells of unknown provenance, the first thing to do was ensure that they were all balanced and showed the same voltage. Some might do this the inefficient way by hooking each one up to a charger and a programmable load, but in this case a much more radical route was taken. A huge PCB was designed with sockets for all hundred cells, connected in parallel through individual series resistors. This allowed them to balance to a common voltage before being discharged to a safe voltage for assembly. Their individual ESRs were the measured, and the best performing examples were then spot-welded into the final 13s-6p final pack.
As a manufacturer of test equipment and more, Tektronix has long had a need for custom form factors with its CRT displays. They initially went with fully glass CRTs as this was what the booming television industry was also using, but as demand for the glass component of CRTs increased, so did the delays in getting these custom glass components made. This is where Tektronix decided to use its existing expertise with ceramic strips during the pre-PCB era to create ceramic funnels for ceramic CRTs, as described in this 1967 video.
The Tektronix ceramic CRT molds underneath Building 13.
Recently, underneath Building 13 at the Tektronix campus, a ‘catacomb’ full of the molds for these funnels was discovered, covering a wide range of CRT types, including some round ones that were presumably made for military purposes, such as radar installations. These molds consist out of an inner part (the mandrel) made from 7075-T6 aluminium, and an outer cast polyurethane boot. The ceramic (forsterite) powder is then formed under high pressure into the ceramic funnel, which is then fired in a kiln before a full inspection and assembly into a full CRT, including the phosphor-coated glass front section and rear section with the electron guns.
The advantages of ceramic funnels over glass ones are many, including the former being much harder and resilient to impact forces, while offering a lot of strength for thinner, lighter structures, all of which is desirable in (portable) lab equipment. Although LCDs would inevitably take over from CRTs here as well, these ceramic CRTs formed an integral part of Tektronix’s products, with every part of production handled in-house.
There’s a mystique among both audiophiles and musicians about vacuum technology, thus having a tube amp still carries a bit of a cachet. New ones can be bought for eye-watering prices and old ones can be had for the same price with the added frisson of unreliability. Happily it’s surprisingly straightforward to build your own, as [_electroidiot] shows us with a fairly inexpensive build.
The design is inspired by the guitar amps of the 1950s and 1960s so it’s not for audiophiles. The circuit is a pretty conventional single-ended one with a two stage double triode preamp and a single power output tube. The transformers are usually the difficult part of a build like this one, and here instead of resorting to using a mains transformer for audio they come from a defunct 1960s Phillips radio. We especially like the old-school construction technique with a folded aluminium chassis and liberal use of tag strips on which to build the circuits.
The result is something that would have been in no way out of place in the 1960s, and proves that tube circuitry isn’t beyond the constructor in 2023. If it’s whetted your appetite for more, we can help you there.
