A Pi Pico Makes A Spectrum Laptop

December 23, 2024 by Jenny List 9 Comments

There are many retrocomputer emulation projects out there, and given the relative fragility of the original machines as they enter their fifth decade, emulation seems to be the most common way to play 8-bit games. It’s easy enough to load one on your modern computer, but there are plenty of hardware options, too. “The computer we’d have done anything for back in 1983” seems to be a phrase many of them bring to mind, but it’s so appropriate because they keep getting better. Take [Stormbytes1970]’s Pi Pico-powered Sinclair ZX Spectrum mini laptop (Spanish language, Google Translate link), for example. It’s a slightly chunky netbook that’s a ZX Spectrum, and it has a far better keyboard than the original.

On the PCB is the Pico, the power supply circuitry, an SD card, and a speaker. But it’s when the board is flipped over that the interesting stuff starts. In place of the squidgy rubber keyboard of yore, it has a proper keyboard,. We’re not entirely sure which switch it uses, but it appears to be a decent one, nevertheless. The enclosure is a slick 3D-printed sub-netbook for retro gaming on the go. Sadly, it won’t edit Hackaday, so we won’t be slipping one in the pack next time we go on the road, but we like it a lot.

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Fixing 1986 Sinclair Spectrum+2 With A High-Score Of Issues

December 19, 2024 by Maya Posch 6 Comments

The Sinclair ZX Spectrum+2 was the first home computer released by Amstrad after buying up Sinclair. It’s basically a Sinclair ZX Spectrum 128, but with a proper keyboard and a built-in tape drive. The one that [Mark] of the Mend it Mark YouTube channel got in for repair is however very much dead. Upon first inspection of the PCB, it was obvious that someone had been in there before, replacing the 7805 voltage regulator and some work on other parts as well, which was promising. After what seemed like an easy fix with a broken joint on the 9 VDC input jack, the video output was however garbled, leading to the real fault analysis.

Fortunately these systems have full schematics available, allowing for easy probing on the address and data lines. Based on this the Z80 CPU was swapped out to eliminate a range of possibilities, but this changed nothing with the symptoms, and a diagnostic ROM cartridge didn’t even boot. Replacing a DS74LS157 multiplexer and trying different RAM chips also made no difference. This still left an array of options on what could be wrong.

Tracking down one short with an IC seemed to be a break, but the video output remained garbled, leaving the exciting possibility of multiple faults remaining. This pattern continues for most of the rest of the video, as through a slow process of elimination the bugs are all hunted down and eliminated, leaving a revived Spectrum+2 (and working tape drive) in its wake, as well as the realization that even with all through-hole parts and full schematics, troubleshooting can still be a royal pain.

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Sinclair BASIC For Today

May 10, 2021 by Al Williams 29 Comments

If you are of a certain age, your first exposure to computer programming was probably BASIC. For a few years, there were few cheaper ways to program in BASIC than the Sinclair ZX series of computers. If you long for those days, you might find the 1980-something variant of BASIC a little limiting. Or you could use SpecBasic from [Paul Dunn].

SpecBasic is apparently reasonably compatible with the Spectrum, but lets you use your better hardware. For example, instead of a 256×192 8-color screen, SpecBas accommodates larger screens and up to 256 colors. However, that does lead to certain incompatibilities that you can read about in the project’s README file.

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Finally! The ROM You Wished Your Sinclair Spectrum Had!

November 27, 2020 by Jenny List 10 Comments

If there is one thing that Sir Clive SInclair was famous for, it was producing electronic devices that somehow managed to squeeze near-impossible performance out of relatively meagre components. This gave us some impressive products, but it’s fair to say that sometimes this philosophy pushed the envelope a little too far. Thus even some of the most fondly remembered Sinclair products concealed significant flaws, and this extended to both their hardware and their software.

The SInclair ZX spectrum’s ROM for example had more than its fair share of bugs, and its BASIC programming experience with single keypress was unique but also slow to run. It’s something [Jonathan Cauldwell] has addressed with his Arcade Game Designer ROM, a complete and ready to run replacement for the original Spectrum ROM that contains a scripting language, a compiler, editors for in-game assets, and a game engine upon which to run your games. It’s the ROM you wanted back in 1983, when you were struggling to fit a bit of Z80 code in a Sinclair Basic REM statement.

If you’re a Spectrum enthusiast and think this sounds a little familiar then you are of course correct. It builds upon his past work with his Arcade Game Designer, with the distribution by ROM allowing the developer to use the full 48k available on all but a very few early 16k machines. You’ll need your own EPROM on which to burn it, but we suspect that if you’re the kind of person who has a Spectrum and has writing these games in mind, you already have access to the relevant equipment.

If you’re new to all this Spectrum stuff and where its ROM came from, then maybe it’s time for a trip down memory lane.

FPGA Raises Component Video From A Sinclair ZX Spectrum

May 25, 2020 by Jenny List 39 Comments

An abiding memory of the early-80s heyday of 8-bit computing for many is operating their computer from the carpet in front of the family TV. While the kids in the computer adverts had parents who bought them a portable colour telly on which to play Jet Set Willy, the average kid had used up all the Christmas present money on the computer itself. The cable would have been an RF connection to the TV antenna socket, and the picture quality? At the time we thought it was amazing because we didn’t know any different, but with the benefit of nearly 40 years’ hindsight, it was awful.

For ZX Spectrum owners in 2020 a standard modification is to bring out a composite video signal, but [c0pperdragon] has gone a step or two beyond that with a component video interface. And this isn’t a mod in which the signals are lifted from the Spectrum’s colour encoder circuitry, instead it uses an FPGA hooked directly to the ULA chip to generate the component video itself.

The Altera chip sits on a little PCB designed to occupy the footprint of the original Astec modulator, and sports a neat bundle of wires hooked up to the various Spectrum signals it needs. There are a couple of jumpers to select the output type and resolution, it supports YPbPr or RGsB outputs and both 288p and 576p. If you think perhaps it looks a little familiar, that’s because it’s the sister project of an earlier board for the Commodore 64. So if you have a Spectrum and are annoyed by UHF and PAL, perhaps it’s worth a look.

The Primordial Sinclair ZX Spectrum Emerges From The Cupboard

March 4, 2019 by Jenny List 12 Comments

The Centre for Computing History in Cambridge, UK, receive many donations from which they can enrich their collection and museum displays. Many are interesting but mundane, but the subject of their latest video is far from that. The wire-wrapped prototype board they reveal with a flourish from beneath a folded antistatic mat is no ordinary computer, because it is the prototype Sinclair ZX Spectrum.

It came to the museum from Nine Tiles, a local consultancy firm that had been contracted by Sinclair Research in the early 1980s to produce the BASIC ROM that would run on the replacement for their popular ZX81 home microcomputer. The write-up and the video we’ve placed below the break give some detail on the history of the ROM project, the pressures from Sinclair’s legendary cost-cutting, and the decision to ship with an unfinished ROM version meaning that later peripherals had to carry shadow ROMs with updated routines.

The board itself is a standard wire-wrap protoboard with all the major Spectrum components there in some form. This is a 16k model, there is no expansion connector, and the layout is back-to-front to that of the final machine. The ULA chip is a pre-production item in a ceramic package, and the keyboard is attached through a D connector. Decent quality key switches make a stark contrast to the rubber keys and membrane that Spectrum owners would later mash to pieces playing Daley Thompson’s Decathlon.

This machine is a remarkable artifact, and we should all be indebted to Nine Tiles for ensuring that it is preserved for those with an interest in computing to study and enjoy. It may not look like much, but that protoboard had a hand in launching a huge number of people’s careers in technology, and we suspect that some of those people will be Hackaday readers. We’ll certainly be dropping in to see it next time we’re in Cambridge.

If you haven’t been to the Centre for Computing History yet, we suggest you take a look at our review from a couple of years ago. And if prototype home computers are your thing, this certainly isn’t the first to grace these pages.

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Bringing Back A Spectrum’s Rails

June 2, 2018 by Jenny List 10 Comments

The Sinclair ZX Spectrum was to most Brits the computer to own in the early 1980s, it might not have had all the hardware features of its more expensive competitors but it had the software library that they lacked. Games came out for the Spectrum first, and then other platforms got them later. If you didn’t have a rubber keyboard and a Sinclair logo, you were nothing in the playground circa 1984. That low price though meant that in true Sinclair tradition a number of corners had been cut in the little micro’s design. Most notably in its power supply, all the various rails required by the memory chips came from a rather insubstantial single-transistor oscillator that is probably the most common point of failure for these classic machines.

[Tynemouth Software] had an Issue 2 Spectrum with a missing -5V rail, and has detailed both the power supply circuit used on these machines and the process of faultfinding and repairing this one. A single transistor oscillator drives a little ferrite-spool transformer from which the various supplies are rectified and filtered. Similar circuits appear in multiple generations of Sinclair hardware, where we might nowadays use a little switching regulator chip.

We’re taken through the various stages of faultfinding this particular circuit, and the culprit is found to be a faulty Zener diode. It’s certainly not the last dead Spectrum that will cross an enthusiast’s bench, but at least in this case, the fault was less obtuse than they sometimes can be in this much-loved but sometimes frustrating machine.

Sinclair enthusiasts might also appreciate the great man’s earliest work.