Reviving A Legend: Mamiya RB67 Repair

April 6, 2023 by 26 Comments
The damaged parts in the camera are circled in red. Original graphic is from the Mamiya service manual.

When it comes to professional medium format analog cameras, the Mamiya RB67 is among the most well-known and loved, ever since its introduction in 1970. Featuring not only support for 120 and 220 film options, but also a folding and ‘chimney’ style view finder and a highly modular body, these are just some reasons that have made it into a popular – if costly – reflex system camera even today. This is one reason why [Anthony Kouttron] chose to purchase and attempt to repair a broken camera, in the hopes of not only saving a lot of money, but also to save one of those amazing cameras from the scrap heap. Continue reading “Reviving A Legend: Mamiya RB67 Repair” →

Even Amstrad Spectrums Need Their Bugs Fixing

April 6, 2023 by 2 Comments

The history of the Sinclair ZX Spectrum is one that mirrors the fortunes of the British home computer industry, one of an early 8-bit boom followed by a sharp decline as manufacturers failed to capitalise on the next generation of 16-bit machines. The grey ZX Spectrum on [Keri Szafir]’s bench is one that encapsulates that decline perfectly, being one of the first models produced under the ownership of Amstrad after Sir Clive’s company foundered. Amstrad made many improvements to the Spectrum, but as she demonstrates, there are still some fixes needed.

The machine came her way because of a hum from the tape deck circuitry. The read amplifier was picking up electrical noise, and she fixed it without mods to the circuit but with the simple expedient of powering the analogue circuit from the tape motor switch so it only works when needed.

Beyond that, this machine demonstrates another ’80s innovation, the SCART/Peritel AV connector. These first appeared on early-80s French TV sets, but by the later half of the decade had made it to the UK where Amstrad included support for an adapter cable from the DIN socket on the back of their Spectrum.  Even then they didn’t get it quite right, and she modifies some links on the board to better support it.

Sinclair were famous for on-board bodges, and even in new ownership continued. There’s a reversed transistor and at least one bodged-on component, but of course, it wouldn’t be a Spectrum without bugs, would it!

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Retrotechtacular: Voice Controlled Typewriter Science Project In 1958

April 6, 2023 by 17 Comments

Hackaday readers might know [Victor Scheinman] as the pioneer who built some of the first practical robot arms. But what was a kid like that doing in high school? Thanks to a film about the 1958 New York City Science Fair, we know he was building a voice-activated typewriter. Don’t believe it? Watch it yourself below, thanks to [David Hoffman].

Ok, we know. Voice typing is no big deal today, and, frankly, [Victor’s] attempt isn’t going to amaze anyone today. But think about it. It was 1958! All those boat anchor ham radios behind him aren’t antiques. That’s what radios looked like in 1958. Plus, the kid is 16 years old. We’d say he did pretty darn good!

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Rock, paper, scissors game that uses servos to choose one at random for the computer.

Forget ChatGPT And Play Rock-Paper-Scissors With Yourself Instead

April 6, 2023 by 3 Comments

This isn’t like the cool AI everyone’s getting caught up with these days, but we’re sure it will make a fun party gimmick nonetheless.

The premise of [CrazyScience]’s game is really simple, with three servos connected to labels that display rock, paper, and scissors, respectively. The game code is written to pick a label to display at random. Furthermore, an ultrasonic distance sensor detects when the player has moved their hand close to the game, indicating the player has chosen a hand and is challenging the game. The result of the game is decided by the player, so we imagine you could pretend you never lost and no one would know.

It would be cool to see the game support multiple players, keep score, or make sure you can never win. And you’ll probably want to add the randomSeed function in the code too. But that seems like a version two problem.

The only thing left to do is add some AI since that’s all we’re doing nowadays. But maybe you’re the type to enjoy the simple 8-bit pleasures instead. If you ask us though, we’d rather play with friends.

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If They Fire The Nukes, Will They Even Work?

April 6, 2023 by 146 Comments

2022 was a harrowing year in a long line of harrowing years. A brutal war in Europe raised the prospect of nuclear war as the leaders behind the invasion rattled sabers and made thinly veiled threats to use weapons of mass destruction. And all this as we’re still working our way through the fallout of a global pandemic.

Those hot-headed threats raise an interesting question, however. Decades have passed since either Russia or the United States ran a live nuclear weapons test. Given that, would the nukes even work if they were fired in anger?

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Finding Paths With Water Is A-Mazing

April 6, 2023 by 18 Comments

We aren’t sure if it qualifies as fluidic logic, but [Steve Mould] was inspired by a simulation of water flowing through a maze and decided to build some actual mazes and watch water flowing through them. It turns out there are several physical effects in play, and you can see [Steve] discuss them in the video below.

The maze, of course, has to be oriented so that water flows into the top and flows out of the bottom. Without much thought, you’d think that the water just goes to the bottom and then fills up. Eventually, the part that is open at the bottom will have water coming out, right? Turns out it isn’t that simple.

A combination of air pressure and surface tension conspire to make the water do better than expected. Not that it perfectly solves it, but it doesn’t just fill up the entire maze, either. Even more interesting is that once the water has found the bottom, changing the water color will clearly show the path through the maze since nearly all of the new colored water will follow the flow path.

Practical? We can’t think of why. But it is a great think piece on how water flows and what sort of forces can affect it.

[Steve] is no stranger to making water work out algorithms, something called fluidic logic.

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Printing Antennas On Circuit Boards

April 6, 2023 by 19 Comments

Yagi-Uda antennas, or simply “Yagis”, are directional antennas that focus radio waves to increase gain, meaning that the radio waves can travel further in that direction for a given transmitter power. Anyone might recognize an old TV antenna on a roof that uses this type of antenna, but they can be used to increase the gain of an antenna at any frequency. This one is designed to operate within the frequencies allotted to WiFi and as a result is so small that the entire antenna can be printed directly on a PCB.

The antenna consists of what is effectively a dipole antenna, sandwiched in between a reflector and three directors. The reflector and directors are passive elements in that they interact with the radio wave to focus it in a specific direction, but the only thing actually powered is the dipole in the middle. It looks almost like a short circuit at first but thanks to the high frequencies involved in this band, will still function like any other dipole antenna would. [IMSAI Guy], who created the video linked above which goes over these details also analyzed the performance of this antenna and found it to be fairly impressive as a WiFi antenna, but he did make a few changes to the board for some other minor improvements in performance.

The creator of these antennas, [WA5VJB] aka [Kent Britain] is an antenna builder based in Texas who has developed a few unique styles of antennas produced in non-traditional ways. Besides this small Yagi, there are other microwave antennas available for direction-finding, some wide-band antennas, and log-periodic antennas that look similar to Yagi antennas but are fundamentally different designs. But if you’re looking to simply extend your home’s WiFi range you might not need any of these, as Yagi antennas for home routers can be a lot simpler than you ever imagined.

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