Digital Paint Mixing Has Been Greatly Improved With 1930s Math

January 30, 2025 by 41 Comments

You might not have noticed if you’re not a digital artist, but most painting and image apps still get color mixing wrong. As we all learned in kindergarten, blue paint and yellow paint makes green paint. Try doing that in Photoshop, and you’ll get something altogether different—a vague, uninspiring brownish-grey. It’s the same story in just about every graphics package out there.

As it turns out, there’s a good reason the big art apps haven’t tackled this—because it’s really hard! However, a team of researchers at Czech Technical University has finally cracked this long-standing problem. The result of their hard work is Mixbox, a digital model for pigment-based color mixing. Once again, creative application of mathematics has netted aesthetically beautiful results!

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A 1962 Test Gear Teardown

January 30, 2025 by 11 Comments

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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Forgotten Internet: Giving (or Getting) The Finger

January 30, 2025 by 27 Comments

Hey, you know that guy in accounting, Marco? If you want to find out more about him, you’d probably go surf LinkedIn or maybe a social media site. Inside a company, you might look on instant messaging for a profile and even find out if he is at his desk or away. But back in the 1970s, those weren’t options. But if Marco was on the computer system, maybe you could finger him. While that sounds strange to say today, Finger was a common service provided by computer services at the time. It was like a LinkedIn profile page for the 1970s.

Based on RFC 742, Finger was the brainchild for [Les Earnest]. From a user’s point of view, you put a few files in your home directory (usually .project and .plan; both hidden files), and when someone “fingered” you, they’d see some human-friendly output about your account like your name and office location, if you were logged in or not, and the contents of your project and plan files.

Modern versions may also show your public PGP key and other data. You could usually put a file in your home directory called .nofinger if you wanted to stop people from fingering you.

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RGB LED Display Simply Solves The Ping-Pong Ball Problem

January 30, 2025 by 19 Comments

A few years ago [Brian McCafferty] created a nice big RGB LED panel in a poster frame that aimed to be easy to move, program, and display. We’d like to draw particular attention to one of his construction methods. On the software end of things there are multiple ways to get images onto a DIY RGB panel, but his assembly technique is worth keeping in mind.

The diameter of ping pong balls is a mismatch for the spacing of LEDs on a strip. The solution? A bit of force.

The technique we want to highlight is not the fact that he used table tennis balls as the diffusers, but rather the particular manner in which he used them. As diffusers, ping-pong balls are economical and they’re effective. But you know what else they are? An inconvenient size!

An LED strip with 30 LEDs per meter puts individual LEDs about 33 mm apart. A regulation ping-pong ball is 40 mm in diameter, making them just a wee bit too big to fit nicely. We’ve seen projects avoid this problem with modular frames that optimize spacing and layout. But [Brian]’s solution was simply to use force.

Observing that ping-pong balls don’t put up much of a fight and the size mismatch was relatively small, he just shoved those (slightly squashy) 40 mm globes into 33 mm spacing. It actually looks… perfectly fine!

We suspect that this method doesn’t scale indefinitely. Probably large displays like this 1200 pixel wall are not the right place to force a square peg into a round hole, but it sure seemed to hit the spot for his poster-sized display. Watch it in action in the video below, or see additional details on the project’s GitHub repository.

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Lessons Learned, When Restoring An Amiga 1000

January 30, 2025 by 9 Comments

In the mid 1980s, there was a rash of 16-bit computers entering the market. One of them stood head and shoulders above the rest: Commodore’s Amiga 1000. It had everything that could reasonably be stuffed into a machine of the period, and multimedia capabilities the rest wouldn’t catch up on for years. [Celso Martinho] has managed to secure one of those first machines, and has shared his tale of bringing it back to life.

The post is as much a love letter to the Amiga and review of A1000 peripherals as it is a restoration, which makes it a good read for retrocomputing enthusiasts.  He recapped it and it wouldn’t boot, the solution of which turned out to be a reminder for the rest of us.

The machine had a RAM upgrade in the form of a daughterboard under the processor, its pins had weakened the leaves of the processor socket so it wouldn’t make contact. So don’t forget to replace sockets as well as capacitors.

The resulting machine is much faster thanks to a modern upgrade with a much quicker processor, memory, and an SD card for storage. He goes into some of the other upgrades available today, all of which would have had early-1990s-us salivating. It’s fair to say that in 2025 an A1000 is more 40-year-old curio than useful modern computer, but we can’t fail to admit to a bit of envy. The Amiga holds a special affection, here.

Inside Vacuum Fluorescent Displays

January 29, 2025 by 2 Comments

VFDs — vacuum fluorescent displays — have a distinctive look, and [Anthony Francis-Jones] is generally fascinated with retro displays. So, it makes sense that he’d build a VFD project as an excuse to explain how they work. You can see the video below.

VFDs are almost miniature CRTs. They are very flexible in what they display and can even use color in a limited way. The project [Anthony] uses as an example is an indicator to show the video number he’s currently making.

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The Guanella 1:1 balun. (Credit: Steve Arar)

Using Guanella Baluns As Impedance Transformers

January 29, 2025 by 2 Comments
Guanella Impedance Transformer. (Credit: FesZ Electronics)
Guanella Impedance Transformer. (Credit: FesZ Electronics)

Even before entering the mystical realms of UHF design, radio frequency (RF) circuits come with a whole range of fun design aspects as well. A case in point can be found in transmission line transformers, which are commonly used in RF power amplifiers, with the Guanella transformer (balun) being one example. Allowing balanced and unbalanced  (hence ‘balun’) systems to interface without issues, they’re both very simple and very complex. This type of transformer and its various uses is explained in a video by [FesZ Electronics], and also the subject of an article by [Dr. Steve Arar] as part of a larger series, the latter of which is recommended to start with you’re not familiar with RF circuitry.

Transmission line transformers are similar to regular transformers, except that the former relies on transmission line action to transfer energy rather than magnetic flux and provides no DC isolation. The Guanella balun transformer was originally described by Gustav Guanella in 1944. Beyond the 1:1 balun other configurations are also possible, which [Dr. Arar] describes in a follow-up article, and which are also covered in the [FesZ] video, alongside the explanation of another use of Guanella transformers: as an impedance transformer. This shows just how flexible transformers are once you can wrap your mind around the theory.

We have previously covered RF amplifier builds as well as some rather interesting balun hacks.

Heading image:  The Guanella 1:1 balun. (Credit: Steve Arar)

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