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.

Accurate Coffee Billing Through Reverse Engineering

May 31, 2018 by Lewin Day 37 Comments

If you’ve ever worked in a stingy office, you’ve become familiar with the communal coffee maker that runs on some variant of the honor system. There’s bits of paper, a coin jar shabbily sealed with sticky tape, and the routine note every six months telling people off for not paying for their daily brew. It all gets a bit much. Thankfully, if you work with [Fabian], it’s no longer a problem (PDF link).

The project forms the basis for [Fabian]’s thesis, in which a DeLonghi coffee maker is reverse engineered. This is undertaken with the explicit goal of properly metering the amount of consumables (coffee beans) used per beverage, to more fairly charge users depending on their brew of choice. This involves breaking down and understanding the coffee maker’s internal communications, as well as implementing a system to record and handle billing. For reasons of simplicity, [Fabian] decided that this should be handled using his colleague’s existing computer accounts. Easy!

It’s a highly academic approach to what we’re sure was a very stimulating project with lots of delicious aromas. Coffee’s a popular topic among hackers, that’s for sure – check out this roaster to take your game to the next level.

Convert A Curbside CRT TV Into An Arcade Monitor

May 30, 2018 by Tom Nardi 29 Comments

While an old CRT TV may work well enough on a MAME cabinet project, the real arcade purists are quick to point out that a proper arcade monitor and a TV aren’t the same thing. A real arcade board uses RGB to connect to the monitor, that is, direct control over the red, green, and blue signals. Conversely video over coax or composite, what most people associate with old CRT TVs, combine all the video information down into an analog signal. Put simply, RGB allows for a much cleaner image than composite.

Many in the arcade restoration scene say that trying to convert a bog standard CRT TV into a RGB monitor isn’t possible, but [Arcade Jason] had his doubts. Over on his YouTube channel, he’s recently posted a tutorial on how to go from a trashed CRT TV to a monitor worthy of proper arcade gaming with relatively little work. As real arcade monitors are becoming increasingly rare, these kind of modifications are likely to get more common as coin-op gamers look to keep the old ways alive.

Now obviously every TV is going to do be different inside. All CRT TVs contain high voltages, and on some the circuit boards aren’t even mains-isolated, so take care if you try this. [Jason] certainly doesn’t claim that the method he demonstrates will work on whatever old TV you happen to have kicking around. But the general idea and some of the techniques he shows off are applicable to most modern TVs, and can help you tailor the method to your particular piece of gear. It all starts with a wet finger. Seriously.

[Jason] demonstrates a rather unique way of determining which pins on the TV’s control chip are responsible for the individual color signals by wetting his finger and sliding it over the pins. When a change in color is seen on the displayed image, you know you’re getting close. We can’t say it’s the most scientific or even the safest method, but it worked for him.

He then follows up with a jumper wire and resistor to find the precise pins which are responsible for each color, and solders up his actual RGB connection for the arcade board. In addition to the three color wires, a sync signal is also needed. This is the same sync signal used in composite video, so all that’s needed is to solder to the pad for the original composite video jack. Add a ground signal, and you’ve got yourself a proper RGB monitor.

Interestingly, this one has come full circle, as [Jason] says his attempt was inspired by an old post on Hackaday. It’s the Circle of Hacker Life.

[Thanks to Seebach for the tip]

Continue reading “Convert A Curbside CRT TV Into An Arcade Monitor” →

VCF East 2018: The Mail Order App Store

May 30, 2018 by Tom Nardi 16 Comments

Today we take the concept of a centralized software repository for granted. Whether it’s apt or the App Store, pretty much every device we use today has a way to pull applications in without the user manually having to search for them on the wilds of the Internet. Not only is this more convenient for the end user, but at least in theory, more secure since you won’t be pulling binaries off of some random website.

But centralized software distribution doesn’t just benefit the user, it can help developers as well. As platforms like Steam have shown, once you lower the bar to the point that all you need to get your software on the marketplace is a good idea, smaller developers get a chance to shine. You don’t need to find a publisher or pay out of pocket to have a bunch of discs pressed, just put your game or program out there and see what happens. Markus “Notch” Persson saw his hobby project Minecraft turn into one of the biggest entertainment franchises in decades, but one has to wonder if it would have ever gotten released commercially if he first had to convince a publisher that somebody would want to play a game about digging holes.

In the days before digital distribution was practical, things were even worse. If you wanted to sell your game or program, it needed to be advertised somewhere, needed to be put on physical media, and it needed to get shipped out to the customer. All this took capital that would easily be beyond many independent developers, to say nothing of single individuals.

But at the recent Vintage Computer Festival East, [Allan Bushman] showed off relics from a little known chapter of early home computing: the Atari Program Exchange (APX). In a wholly unique approach to software distribution at the time, individuals were given a platform by which their software would be advertised and sold to owners of 8-bit machines such as the Atari 400/800 and later XL series computers. In the early days, when the line between computer user and computer programmer was especially blurry, the APX let anyone with the skill turn their ideas into profit. Continue reading “VCF East 2018: The Mail Order App Store” →

Rolling Old School With Copy Protection From The 1980s

May 27, 2018 by Dan Maloney 47 Comments

Oh, for the old days when sailing the seas of piracy was as simple as hooking a couple of VCRs together with a dubbing cable. Sure, the video quality degraded with each generation, but it was so bad to start out with that not paying $25 for a copy of “Ghostbusters” was a value proposition. But then came The Man with all his “rules” and “laws” about not stealing, and suddenly tapes weren’t so easy to copy.

If you’ve ever wondered how copy protection worked in pre-digital media, wonder no more. [Technology Connections] has done a nice primer on one of the main copy protection scheme from the VHS days. It was dubbed “Analog Protection System” or “Analog Copy Protection” by Macrovision, the company that developed it. Ironically, Macrovision the company later morphed into the TiVo Corporation.

The idea for Macrovision copy protection was to leverage the difference between what a TV would accept as a valid analog signal and what the VCR could handle. It used the vertical blanking interval (VBI) in the analog signal, the time during which the electron beam returns to the top of the frame. Normally the VBI has signals that the VCR uses to set its recording levels, but Macrovision figured out that sending extra signals in the VBI fooled the VCR’s automatic gain controls into varying the brightness of the recorded scenes. They also messed with the vertical synchronization, and the effect was to make dubbed tapes unwatchable, even by 1985 standards.

Copy protection was pretty effective, and pretty clever given the constraints. With Digital Rights Management, it’s easier to put limits on almost anything — coffee makers, arcade games, and even kitty litter all sport copy protection these days. It almost makes us nostalgic for the 80s.

Continue reading “Rolling Old School With Copy Protection From The 1980s” →

VCF East 2018: The Desktop ENIAC

May 24, 2018 by Tom Nardi 23 Comments

The ENIAC, or Electronic Numerical Integrator and Computer, is essentially the Great Great Grandfather of whatever device you’re currently reading these words on. Developed during World War II for what would be about $7 million USD today, it was designed to calculate artillery firing tables. Once word got out about its capabilities, it was also put to work on such heady tasks as assisting with John von Neumann’s research into the hydrogen bomb. The success of ENIAC lead directly into the development of EDVAC, which adopted some of the now standard computing concepts such as binary arithmetic and the idea of stored programs. The rest, as they say, is history.

But ENIAC wasn’t just hugely expensive and successful, it was also just plain huge. While it’s somewhat difficult for the modern mind to comprehend, ENIAC was approximately 100 feet long and weighed in at a whopping 27 tons. In its final configuration in 1956, it contained about 18,000 vacuum tubes, 7,000 diodes, 70,000 resistors, 10,000 capacitors, and 6,000 switches. All that hardware comes with a mighty thirst for power: the ENIAC could easily suck down 150 kW of electricity. At the time this all seemed perfectly reasonable for a machine that could perform 5,000 instructions per second, but today an Arduino would run circles around it.

This vast discrepancy between the power and size of modern hardware versus such primordial computers was on full display at the Vintage Computer Festival East, where Brian Stuart demonstrated his very impressive ENIAC emulator. Like any good vintage hardware emulator, his project not only accurately recreates the capabilities of the original hardware, but attempts to give the modern operator a taste of the unique experience of operating a machine that had its heyday when “computers” were still people with slide rules. Continue reading “VCF East 2018: The Desktop ENIAC” →

A Smarter PSU Converter Leaves The Magic Smoke Inside

May 24, 2018 by Lewin Day 24 Comments

Over the years, computers have become faster, but at the same time, more power hungry as well. Way back around the 386 era, most PCs were using the AT standard for power supplies. Since then, the world moved on to the now ubiquitous ATX standard. Hobbyists working on older machines will typically use these readily available supplies with basic adapters to run old machines, but [Samuel] built a better one.

Most AT to ATX adapters are basic passive units, routing the various power lines where they need to go and tying the right pin high to switch the ATX supply on. However, using these with older machines can be fraught with danger. Modern supplies are designed to deliver huge currents, over 20 A in some cases, to run modern hardware. Conversely, a motherboard from the early 90s might only need 2 or 3A. In the case of a short circuit, caused by damage or a failed component, the modern supply will deliver huge current, often damaging the board, due to the overcurrent limit being set so high.

[Samuel]’s solution is to lean on modern electronics to build an ATX to AT adapter with programmable current protection. This allows the current limit to be set far lower in order to protect delicate boards. The board can be set up in both a “fast blow” and a “slow blow” mode to suit various working conditions, and [Samuel] reports that with alternative cabling, it can also be used to power up other old hardware such as Macintosh or Amiga boards. The board is even packed with extra useful features like circuitry to generate the sometimes-needed -5V rail. It’s all programmed through DIP switches and even has an OLED display for feedback.

It’s an adapter that could save some rare old hardware that’s simply irreplaceable, and for that reason alone, we think it’s a highly important build. We’ve talked about appropriate fusing and current limiting before, too – namely, with LED strips.