TI(ny) Is A New Take On The TI-99/4A

September 12, 2018 by Zoe Skyforest 23 Comments

Way back in the 1980s, in the heyday of the personal computer revolution, Texas Instruments were one of the major players. The TI-99/4A was one of their more popular machines, selling 2.8 million units after an epic price war with the Commodore VIC-20. However once it had been discontinued, fans were left wanting more from the platform. Years later, that led [Fabrice] to produce the TI(ny), his take on an upgraded, more integrated TI-99/4A (Google Translate link).

Having spent many years working on these machines, [Fabrice] was very familiar with the official TI schematics – regarding both their proper use and their errors, omissions and inaccuracies. With a strong underlying knowledge of what makes a TI-99/4A tick, he set out to pen his own take on an extended model. [Fabrice] rolls in such features as Atari-compatible joystick ports, slot connectors for PeBOX expansion cards, and an RGB video output. It’s then all wrapped up in a very tidy looking case of somewhat unclear construction; it appears to be modified from an existing small computer case, and then refinished to look almost stock.

The best detail, though? It’s all made with components available in 1983! We see a lot of retro builds that are the equivalent of throwing a modern fuel-injected V8 into a vintage muscle car, and they are fantastic – but this is a project that shows us what was possible way back when.

Overall it’s a tidy build that shows what the TI-99/4A could have been if it was given a special edition model at the end of its life. If you’re looking to relive the glory days of the machine yourself, what better way then firing up the best demo on the platform? As the saying goes – Don’t Mess With Texas.

[Thanks to g_alen_e for the tip!]

ATX Adapter For The IBM PCJr Now Available

September 10, 2018 by Tom Nardi 4 Comments

We’ve mentioned previously the challenges that come with maintaining vintage computers which in some cases are pushing 40 years old. Components, even high quality ones, eventually fail and need to be replaced. Now if it’s a fairly popular vintage machine, replacement parts usually aren’t too hard to come by. But what if you’re dealing with a machine that’s not just vintage, but was also such a commercial flop that parts are scarce?

Such is the life for anyone who owns one of the 500,000 IBM PCJrs that Big Blue managed to get out of the door during the year or so the product was on the market. As [AkBKukU] found, a replacement AC adapter for the odd-ball computer was going to cost more than what he paid for the thing, so he set to work on creating an adapter so he could use a modern ATX PSU on the machine. After a couple of months of ironing out the kinks, the design is finally ready for consumption.

In the end, the PCB design itself is quite simple. It’s really just a matter of switching around some pins from the standard ATX plug to the edge connector on the PCJr. There’s also a connector for powering a floppy drive, as well as headers for a fan and power switch.

[AkBKukU] has come up with two ways to use the adapter. You can either go with a standard ATX PSU, in which case it will need to sit outside the machine due to its size, or use a PicoPSU which allows you to keep the whole thing internal. If you don’t mind spending the cash, the PicoPSU method is a much cleaner installation that still provides plenty of power. Depending on which route you take, there are different 3D printed plates to adapt the computer’s rear panel to fit the new hardware.

All the files to build your own version are in the GitHub repository, and [AkBKukU] is doing some low volume runs of both kits and assembled adapter. If this project looks familiar, it’s because we reported on it back when it was still a hand-scratched PCB that didn’t always work as expected.

[Thanks to Gregg for the tip.]

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A Switching Power Supply, 1940s-Style

September 8, 2018 by Dan Maloney 26 Comments

“They don’t build ’em like they used to.” There’s plenty of truth to that old saw, especially when a switch-mode power supply from the 1940s still works with its original parts. But when said power supply is about the size of a smallish toddler and twice as heavy, building them like the old days isn’t everything it’s cracked up to be.

The power supply that [Ken Shirriff] dives into comes from an ongoing restoration of a vintage teletype we covered recently. In that post we noted the “mysterious blue glow” of the tubes in the power supply, which [Ken] decided to look into further. The tubes are Thyratrons, which can’t really be classified as vacuum tubes since they’re filled with various gasses. Thyratrons are tubes that use ionized gas – mercury vapor in this case – to conduct large currents. In this circuit, the Thyratrons are used as half-wave rectifiers that can be rapidly switched on and off by a feedback circuit. That keeps the output voltage fixed at the nominal 140V DC required by the teletype, with a surprisingly small amount of ripple. The video below is from a series on the entire restoration; this one is cued to where the power supply is powered up for the first time. It’s interesting to see the Thyratrons being switched at about 120 Hz when the supply is under load.

Cheers to [Ken] and his retrocomputing colleagues for keeping the old iron running. Whether the target of his ministrations is a 1974 scientific calculator or core memory from an IBM 1401, we always enjoy watching him work.

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Detective Work Recovers Atari ST ASIC Designs

September 5, 2018 by Al Williams 28 Comments

[Christian Zietz] wanted to know more about the Atari ST. He found information online from newer Atari machines like the Falcon030 and the Jaguar, but couldn’t find much else. While looking through some archives of old disk images from the Atari headquarters, he found a folder marked “Drawings\4118.” With some detective work and emulation of an old operating system, he was able to recover the schematics for the ST-4118 video shifter ASIC (Application-Specific Integrated Circuit).

Unfortunately, this appeared to be a chip for the unreleased Atari Panther video game console. However, it did show the way to how these older schematics were readable. [Christian] continued searching and found some floppy disk images that were a bit unusual. They didn’t have a proper file system but had been created by a backup program called FastBack for MS-DOS.

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NASA Shows Off Its Big Computer In 1986

August 28, 2018 by Al Williams 55 Comments

Sometimes it is hard to remember just how far computers have come in the last three or four decades. An old NASA video (see below) has been restored with better sound and video recently that shows what passed for a giant computer in 1986. The Cray 2 runs at 250 MHz and had two gigabytes of memory (256 ~~megabytes of~~ million 64-bit words).

Despite the breathless praise, history hasn’t been kind to the Cray 2. Based on ECL, it had 4 processors and –in theory — could reach 1,900 megaFLOPs/second (a FLOP is a floating point operation). However, practical problems made it difficult to get to that theoretical maximum.

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Recreating The Amiga 1200 PCB From Pictures

August 28, 2018 by Tom Nardi 35 Comments

In the past we’ve talked about one of the major downsides of working with vintage computer hardware, which of course is the fact you’re working with vintage computer hardware. The reality is that these machines were never designed to be up and running 20, 30, or even 40-odd years after they were manufactured. Components degrade and fail, and eventually you’re going to need to either find some way to keep your favorite classic computer up and running or relegate it to becoming a display piece on the shelf.

If you’re like [John Hertell], you take the former option. Knowing that many an Amiga 1200 has gone to that great retrocomputing museum in the sky due to corroded PCBs, he decided to recreate the design from scans of an unpopulated board. While he was at it, he tacked on a few modern fixes and enhancements, earning his new project the moniker: “Re-Amiga 1200”.

To create this updated PCB, [John] took high quality scans of an original board and loaded them up into Sprint Layout, which allows you to freely draw your PCB design over the top of an existing image. While he admits the software isn’t ideal for new designs, the fact that he could literally trace the scan of the original board made it the ideal choice for this particular task.

After the base board was recreated in digital form, the next step was to improve on it. Parts which are now EOL and hard to come by got deleted in place of modern alternatives, power traces were made thicker, extra fan connectors were added, and of course he couldn’t miss the opportunity to add some additional status blinkenlights. [John] has released his Gerber files as well as a complete BOM if you want to make your own Re-Amiga, and says he’ll also be selling PCBs if you don’t want to go through the trouble of getting them fabricated.

It seems as if Amiga fans never say never, as this isn’t the first time we’ve seen one brought back from the brink of extinction by way of a modernized motherboard. Whatever it takes to keep the vintage computing dream alive.

[Thanks to Anders for the tip.]

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Using Modern Nintendo Controllers On The C64

August 23, 2018 by Tom Nardi 12 Comments

There are plenty of people out there who still enjoy playing games on vintage computers like the Commodore 64. But while they likely return to these classic games themselves out of a sense of nostalgia, the feeling doesn’t always extend to the hardware itself. For example, one can enjoy playing Impossible Mission without having to use a contemporary C64 joystick.

Thanks to an open source project developed by [Robert Grasböck], C64 owners who want to take advantage of the improvements made to gaming controllers in the nearly 40 years since the system’s release now have another option. Called Nunchuk64, it allows you to use various Nintendo controllers which make use of the Wii “Nunchuk” interface on original C64 hardware. This includes the controllers from the recent “Classic Edition” NES and SNES systems, which offer a decidedly retro feel with all the benefits of modern technology and construction techniques.

Both the hardware and software for Nunchuck64 are open source, and everything you need to build your own version is in the project’s repository. [Robert] even has assembly instructions, complete with images, which walk you through building your own copy of the hardware and flashing the firmware onto it. This is a nice touch that we very rarely see even in open source projects. The board is populated with a ATmega328P microcontroller and a handful of passive components, making assembly fairly straightforward assuming you are comfortable with SMD work.

Bringing more modern controllers to classic systems seems to be gaining popularity recently, within the last few months we’ve seen Xbox 360 controllers on the Nintendo 64, and newly manufactured pads for the Atari 5200.

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