This Relay Computer Has Magnetic Tape Storage

June 11, 2025 by Jenny List 8 Comments

Magnetic tape storage is something many of us will associate with 8-bit microcomputers or 1960s mainframe computers, but it still has a place in the modern data center for long-term backups. It’s likely not to be the first storage tech that would spring to mind when considering a relay computer, but that’s just what [DiPDoT] has done by giving his machine tape storage.

We like this hack, in particular because it’s synchronous. Where the cassette storage of old just had the data stream, this one uses both channels of a stereo cassette deck, one for clock and the other data. It’s encoded as a sequence of tones, which are amplified at playback (by a tube amp, of course) to drive a rectifier which fires the relay.

On the record side the tones are made by an Arduino, something which we fully understand but at the same time can’t help wondering whether something electromechanical could be used instead. Either way, it works well enough to fill a relay shift register with each byte, which can then be transferred to the memory. It’s detailed in a series of videos, the first of which we’ve paced below the break.

If you want more cassette tape goodness, while this may be the slowest, someone else is making a much faster cassette interface. Continue reading “This Relay Computer Has Magnetic Tape Storage” →

In Film, What’s Old May Still Be New Again

June 6, 2025 by Jenny List 15 Comments

We recently published an affectionate look at a Polaroid Land camera, whose peel-apart instant film is long out of production except for a very few single exposure packs form a boutique manufacturer. All that was left was a discussion of modifying it for conventional roll film, or perhaps hacking a modern back-to-front Polaroid sheet into it.

Never say never though, because along come the Chinese company Light Lens Lab with a short announcement at the end of a post talking about grain structures and anti-halation layer materials for their black and white film.

Lastly, with our future development plan, we are currently developing and researching instant peel-apart film, with plans on producing and making available black and white peel-apart film by 2025 in various format. We aim to have an update on our packaging and test shot for the next development/research progress installment. We are also researching, developing and producing colour reversal films that consist of a dye-incorporating development process, commonly known as K-14, for 135 and 120 formats in 2026.

So there you go, no sooner has Hackaday declared a format unavailable, than it shows every sign of reappearing. At this point we’d like to take the opportunity to report that McDonalds Szechuan Chicken McNugget sauce will never ever be available again. Continue reading “In Film, What’s Old May Still Be New Again” →

A Steady Vacuum For The Fastest Cassette Tape Drive Ever

June 5, 2025 by Jenny List 39 Comments

If you think of a 1960s mainframe computer, it’s likely that your mental image includes alongside the cabinets with the blinkenlights, a row of reel-to-reel tape drives. These refrigerator-sized units had a superficial resemblance to an audio tape deck, but with the tape hanging down in a loop either side of the head assembly. This loop was held by a vacuum to allow faster random access speeds at the head, and this fascinates [Thorbjörn Jemander]. He’s trying to create a cassette tape drive that can load 64 kilobytes in ten seconds, so he’s starting by replicating the vacuum columns of old.

The video below is the first of a series on this project, and aside from explaining the tape drive’s operation, it’s really an in-depth exploration of centrifugal fan design. He discovers that it’s speed rather than special impeller design that matters, and in particular a closed impeller delivers the required vacuum. We like his home-made manometer in particular.

What he comes up with is a 3D printed contraption with a big 12 volt motor on the back, and a slot for a cassette on the front. It achieves the right pressure, and pulls the tape neatly down into a pair of loops. We’d be curious to know whether a faster motor such as you might find in a drone would deliver more for less drama, but we can see the genesis of a fascinating project here. Definitely a series to watch.

Meanwhile, if your interest extends to those early machine rooms, have a wallow in the past.

Continue reading “A Steady Vacuum For The Fastest Cassette Tape Drive Ever” →

A Vintage ‘Scope Comes Back To Life

June 4, 2025 by Jenny List 3 Comments

We’re suckers for a vintage electronic teardown here at Hackaday, and thus it’s pleasing to see [Thomas Scherrer OZ2CPU] with a 1962 AEG oscilloscope on his bench. It’s definitely seen better days, and is a single-trace 10 MHz unit of the type you might have seen in a typical general purpose electronics lab back in the day.

Pulling the cover off, and as expected there’s a row of tubes each side of the centrally mounted CRT. No printed circuits in sight, and no transistors either, though the rectifiers are selenium parts. After a clean-up it’s time to look at the tubes, and they show the metallic deposits characteristic of long operation. We’re more used to that from older televisions than test equipment,

Gently bringing the power up it looks promising, but there’s a purple glow from one of the PCL82 triode-pentodes. Replacing that and a double-triode results in a ‘scope that surprisingly, is working. It was evidently a high quality device in the first place, with components capable of lasting for over six decades.

We’ve seen more from his bench involving tubes, including this device using a magic-eye tube as the heavy lifter.

Continue reading “A Vintage ‘Scope Comes Back To Life” →

Spin-Casting This Telescope Mirror In Resin Didn’t Go To Plan

June 3, 2025 by Lewin Day 29 Comments

For most of us, mirrors are something we buy instead of build. However, [Unnecessary Automation] wanted to craft mirrors of his own for a custom telescope build. As it turns out, producing optically-useful mirrors is not exactly easy.

For the telescope build in question, [Unnecessary Automation] needed a concave mirror. Trying to get that sort of shape with glass can be difficult. However, there’s such a thing as a “liquid mirror” where spinning fluid forms into a parabolic-like shape. Thus came the idea to spin liquid resin during curing to try and create a mirror with the right shape.

That didn’t quite work, but it inspired a more advanced setup where a spinning bowl and dense glycerine fluid was used to craft a silicone mold with a convex shape. This could then be used to produce a resin-based mirror in a relatively stationary fashion. From there, it was just necessary to plate a shiny metal layer on to the final part to create the mirror effect. Unfortunately, the end result was too messy to use as a viable telescope mirror, but we learn a lot about what didn’t work along the way.

The video is a great journey of trial and error. Sometimes, figuring out how to do something is the fun part of a project, even if you don’t always succeed. If you’ve got ideas on how to successfully spin cast a quality mirror, drop them in the comments below. We’ve seen others explore mirror making techniques before, too.

Continue reading “Spin-Casting This Telescope Mirror In Resin Didn’t Go To Plan” →

The Keyboard Sinclair Never Made

June 2, 2025 by Heidi Ulrich 21 Comments

For those of us who’ve spent far too long hammering rubber keys into submission, a glorious solution has arrived. [Lee Smith] designed the ZX Mechtrum Deluxe, the ultimate keyboard upgrade for your beloved ZX Spectrum 48k. Thanks to [morefunmakingit], you can see this build-it-yourself mechanical mod below. It finally brings a proper spacebar and Spectrum-themed Wraith keycaps into your retro life.

The Metrum Deluxe is a full PCB redesign: no reused matrices or clunky membrane adapters here. [Lee Smith] got fed up with people (read: the community, plus one very persistent YouTuber) asking for a better typing experience, so he delivered. Wraith keycaps from AliExpress echo the original token commands and BASIC vibe, without going full collector-crazy. Best of all: the files are open. You can download the case on Printables and order the PCB through JLCPCB. Cherry on top (pun intended): you’ll finally have a spacebar your thumbs can be proud of.

So whether you’re into Frankenstein rigs or just want your Spectrum to stop feeling like an air mattress, check this video out. Build files and link to the keycaps can be found on Youtube, below the video.

Tip: if you foster a secret love for keyboards, don’t miss the Keebin’ with Kristina’s series on all sorts of keyboards.

Continue reading “The Keyboard Sinclair Never Made” →

Planetary Poetry With A Tiny Digital Core

June 2, 2025 by Heidi Ulrich 7 Comments

Some hacks just tickle the brain in a very particular way. They’re, for a change, not overly engineered; they’re just elegant, anachronistic, and full of mischief. That’s exactly what [Frans] pulls off with A Gentleman’s Orrery, a tiny, simple clockwork solar system. Composed of shiny brass and the poise of 18th-century craftsmanship, it hides a modern secret: there’s barely any clockwork inside. You can build it yourself.

Peek behind the polished face and you’ll find a mechanical sleight of hand. This isn’t your grandfather’s gear-laden planetarium. Instead of that, it operates on a pared-down system that relies on a stepper motor, driving planetary movement through a 0.8 mm axle nested inside a 1 mm brass tube. That micro-mechanical coupling, aided by a couple of bevel gears, manages to rotate the Moon just right, including its orientation. Most of the movement relies on clever design, not gear cascades. The real wizardry happens under the hood: a 3D-printed chassis cradles an ESP32-C6, a TTP223 capacitive touch module, STSPIN220 driver, and even a reed switch with magnetic charging.

You can even swap out the brass for a stone shell where the full moon acts as the touch control. It’s tactile, it’s poetic, and therefore, a nice hack for a weekend project. To build it yourself, read [Frans]’ Instructable.

Continue reading “Planetary Poetry With A Tiny Digital Core” →