A Camera Viewfinder Makes A Great TV

May 31, 2026 by No comments

When we think of CRT camera viewfinders, most of us probably imagine the tiny CRTs you’d find in a 1980s camcorder. They’re super cute and a load of fun to play with, but they’re very much a consumer device. Professional cameras of the type you’d find in a studio had their own viewfinders, which were a lot closer to a small TV. They’re about as high quality as it gets for a monochrome CRT, and [Evan Monsma] has done the conversion to a general-purpose monitor.

On one side, this is a very straightforward hack, simply a case of tracing wires to identify the power and video pins. Given a tool battery, the monitor fires up and gives a super-sharp picture. What we like about this is the wooden base he’s made for the thing, at the same time rough-and-ready, and professional-looking from the outside. It has a routed space for the cables, and once mounted flush with the monitor base and given a bit of wood stain, it looks almost as though it was manufactured that way.

It’s likely most of us won’t find a broadcast viewfinder in the trash, instead settling at best for a little Chinese portable TV. But it’s still interesting to see these unusual devices. Perhaps it might make a good cyberdeck.

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4-bit Relay Logic Counter Begs To Have Its Buttons Pushed

May 31, 2026 by No comments

What’s one to do with some nice little relays of questionable pinout, and prototyping board? How about a quietly clicky 4-bit counter using relay logic with tons of buttons?

The register with LEDs and buttons is on the top board, the incrementer on the bottom board.

[Agatha Mallett] made the counter after finding herself in possession of a quantity of relays burdened by terrible documentation (the datasheet shockingly lacks a pinout, and doesn’t even mention the coil being unidirectional). But since the relays are also small and of decent quality, they were a good candidate for a small relay logic-based project.

The key to the build is implementing D-type flip-flops using relays. This is done by holding the coil voltage of each relay between its set and release voltage levels. A small voltage bump will energize the coil, closing the relay and leaving it closed. Conversely, a small negative spike releases the coil, leaving it open. This forms the basis of the counter, and [Agatha] has a separate write-up all about the details of using relays in this way.

Implementing this was rather less straightforward than it may sound because it relies on balancing the coils of many relays on a figurative knife-edge of voltage, but not every component is perfectly identical. A tweaked resistor or capacitor here and there was needed before things settled into reliability.

The end product has indicator LEDs, buttons to increment or clear the current count, and it even has buttons to set or clear individual bits. This is a project that begs to be interacted with, and there’s a short video on the project page so you can watch it go through its paces.

Thanks to [Jess] for the tip!

Loading Sega Genesis Games Off A Vinyl Record

May 31, 2026 by 6 Comments

Recently [Throaty Mumbo] took a poke at another daft idea, in the form of loading Sega Genesis games off vinyl records. Although a whacky idea, it’s made possible through the use of a Mega Everdrive Pro and its ability to load games via its USB port, a feature mostly intended for on-the-fly game development without swapping SD cards.

For a few decades in home computing, the loading of software from cassette tapes and similar media was very common. This was due to the low-cost nature of this ubiquitous technology compared to alternatives like cartridges and floppy disks. Even if it was famously unreliable and slow, this accessibility made it a very popular choice. This is where home game consoles were different, as they generally used very fast cartridges, but what if you merge these two worlds?

As demonstrated, a Pico 2 board with its RP2350 MCU is used to convert the audio signal containing the binary data into data for transmission via USB to the Everdrive cartridge. After confirming that it works with a tape drive, he drags in a plastic-y PO-80 5″ record cutter and player, where the mono audio limitation is not a problem.

Unfortunately, this PO-80 turns out to be exactly the kind of toy it looks like, with [Throaty Mumbo] unable to cut and play back a record that gets a clean enough signal to the Pico 2 board, though with a better player and likely record cutter it should work fine. After all, some magazines back in the day came with plastic ‘vinyl’ records that contained programs you could load from your record player.

Although technically a failure, it does demonstrate that if you are very patient, you can totally load Sega Genesis ROMs off a tape or record at a blistering couple of kB/s, tops.

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Ebike Display Uses Reflective LCD

May 31, 2026 by 9 Comments

Although LCD displays have been used in almost every type of consumer electronics display over the last two decades, many of these screens have a few downsides that limit their usefulness in certain situations. As any owner of an early digital watch, an early laptop, or an early digital camera will testify, these displays often completely fail in direct sunlight. And, a currently new technology often using inexpensive displays in full sunlight conditions is ebikes, so [Volos Projects] decided to use a unique LCD display to solve this issue.

The display is called a reflective LCD (RLCD) and is actually a fairly old but overlooked piece of technology. Displays like these have a reflective layer that bounces ambient light back to the user, increasing contrast and readability in high light, especially when compared to more common transmissive displays. This build is based on a board from Waveshare, which includes the screen and its driver components, and [Volos Projects] integrated this into a test stand that mimics an ebike’s speed sensor and other hardware like turn signals. The display shows the bike’s speed and a few other indicators, and thanks to the screen, this information can be easily seen in full sun.

Although he doesn’t have it on an actual e-bike yet, he hopes it will be useful for those who want to try out something like this with their substandard e-bike displays. The code he’s used is available on a GitHub page for anyone interested. We’d imagine that a low-cost display like this would pair well with an open-source ebike like this one.

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Modern Graphics Via DisplayLink For Your ISA-Era PC

May 31, 2026 by 7 Comments

The monitors used on older computers are now becoming difficult to find, as we doubt anything for MDA, CGA, Hercules, or EGA has been manufactured in decades. Even VGA, though there are plenty of surplus flat panels to be found, is not as ubiquitous as it once was. Where does that leave the retrocomputing enthusiast with an ISA PC and no screen? Perhaps [Ian Hanschen] has the answer with the PicoGraph, an ISA-to-USB-to-Displaylink adapter.

In hardware terms, it’s using a PicoMEM, a more general-purpose ISA card for emulating cards with a Pi Pico. The Pico hosts a USB DisplayLink adapter, which can connect to the screen of your choice. The software on the PicoMEM does the heavy lifting and provides MDA, Herc, EGA, and VGA support, as well as support for one of the 1990s Cirrus Logic SVGA chipsets. And yes, it appears to work with DOOM.

The practice of using 2020s microcontrollers to lend functionality to retrocomputers has revolutionised the art. We’ve seen many, with one of the more recent being a minimap add-on for an 8-bit Sinclair Spectrum.

A 3D printer hotend with four filament leads in positioned on an arm above a hole in a glass plate. Wires lead from a carbon fiber frame under the glass to four stepper motors with pulleys.

The Final Steps To A Sub-Minute Benchy

May 30, 2026 by 13 Comments

In 2024, [Jan Roetz] decided to see whether he could 3D print a Benchy – the boat-shaped benchmarking tool used in 3D printer calibration – in less than one minute. Two years later, after experiments with air bearing print beds, dry ice cooling, multi-filament hotends, and more, he’s finally broken the one-minute mark.

There are three primary factors limiting the speed of the printer: the extrusion flow rate, the cooling rate for extruded plastic, and the motion system itself. The printer’s hotend combines four strands of filament in one hotend and can extrude about 400 cubic millimeters of plastic per second. For cooling, an air duct around the nozzle could deliver about 400 liters of air per minute, which left the motion system as the only bottleneck.

The original print bed was on top of an air bearing on a granite base, and its motion could be controlled by cords connected to stepper motors. This whole system had very low friction, but its inertia was too high. [Jan] therefore replaced the build plate with a lighter carbon-fiber frame. This had no air bearing, but it slid between the base granite slab and a glass plate above it, which had an opening above the portion used as a build plate. Even the metal pulleys used on the stepper motors had too much inertia, so [Jan] replaced them with smaller, semi-circular plastic pulleys.

The first test was a sub-60-second dry run to make sure nothing would break. This revealed the need for cable guides to keep them from whipping around (not surprising when they were pulling the bed at an acceleration of 225 G). Finally, [Jan] was able to successfully print several successive 59-second Benchies. The prints weren’t photogenic, but they were mechanically sound and dimensionally correct. [Jan] could have gone even faster, but this degraded the print quality too much.

It’s quite an accomplishment, and an impressive conclusion to a major project; we covered the beginning of the project back when [Jan] was going for parallelization rather than speed. The final print didn’t use it, but he also experimented with dynamic temperature control.

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Poking Around With JTAG On A Guitar Amp

May 30, 2026 by 5 Comments

You would think a guitar amplifier would be a straightforward piece of analog electronics. But, of course, these days, everything has firmware, including [mforney]’s Yamaha THR10c. The service manual showed both a UART and JTAG header on the schematic, so as many of us would, he took that as a challenge.

Of course, the production board doesn’t have headers for these ports, but that’s not a real problem. The serial port seemed quiet, but the JTAG port was more productive. This revealed two binary images: a bootloader and the main firmware. Once you have the code, it is a straightforward, if not laborious, process to reverse engineer what the code does.

The next step is to figure out how to load new firmware. You can see in the post that this was done, and custom features sprang into life with custom-patched firmware.

We never get tired of seeing people dig into consumer devices like this. Things like JTAG and the wide availability of JTAG tools have made it easier but no less fun. Of course, there are even more features [mforney] has in mind, but now that’s just a matter of coding.