Computer Space Flies Again

November 10, 2022 by Jonathan Bennett 11 Comments

[Sean] from Classic Arcade Repairs fixes classic arcade machines, and he got a request to repair a very special machine. It’s Computer Space, the first commercial arcade cabinet ever made, and loosely based on Spacewar! This grand-daddy of coin-op was a literal barn find, and was in pretty bad shape after sitting for years. All the parts appeared to be original, making them 50 years old. As you can imagine, that combination didn’t bode well for the health of the components. There’s a couple hours of footage here, but it’s invaluable troubleshooting advice, and very cool to see such an old machine being worked on.

Part one is the intro, and [Sean] started with an HP logic analyzer, just probing the many TTL chips on the board looking for floating or otherwise suspicious outputs. Figure out the obviously faulty chips and replace each with a socket and new chip. Just about every diode in the machine needed replacing.

Part two of the repair starts with a broken trace repair, and the discovery that all the ceramic capacitors on the boards were leaky. The interesting thing is that a multimeter tested those caps as having the correct capacitance, but a dedicated leak tester discovered the problem.

Part 3 shows the process of running the remaining chips through a logic tester, which found more problematic ICs. In some cases, a chip would only sometimes test as working. And strangely, one of the new, replacement chips turned out to have a problem. Though as a commenter pointed out, it could be a falling edge vs rising edge variation of the logic chips to blame. Or maybe the new chips were counterfeit. Hard to nail down.

Part 4 starts with a gotcha moment, where one of the first repairs to the board was a misstep. What appeared to be a damaged trace, was actually a factory modification (a bodge cut?). Then a lucky break really helped out, where only half of one of the 7476 chips was in use, and one of the chips on hand was only half working. Put the dead bit into the unused slot, and the machine really started to behave.

Part 5 is the victory lap, where all the components finally arrived, and everything starts working on the bench. How cool to see the old machine bleeping and blooping again.

DIY SpaceNavigator Brings The Freedom

November 9, 2022 by Jonathan Bennett 25 Comments

[Pepijn de Vos] wanted a 6DOF HID. You know, a 6 Degrees Of Freedom Hardware Interface Device. Those are the fancy controllers for navigating in 3D space, for uses like Computer Aided Design, or Kerbal Space Program. And while we can’t speak to [Pepijn]’s KSP addiction, we do know that the commercially available controllers are prohibitively expensive. It takes some serious CAD work to justify the expenditure. [Pepijn] falls somewhere in-between, and while he couldn’t justify the expense, he does have the chops to design and 3D print his own.

Marvelously, he’s shared the design files for SpaceFox, linked above. It’s 6 spring-loaded potentiometers, supporting a floating printed Big Knob. The pots feed into an Arduino Pro Micro, which calculates the knob’s position on the fly and feeds in into the connected computer. On the computer side, the project uses the spacenavd driver to interface with various applications.

SpaceFox V1 is essentially a proof of concept, just asking for someone to come along and knock off the rough edges. [Pepijn] even includes a wishlist of improvements, but with the caveat that he’s satisfied with his working model. If this project really gets your 6DOF juices flowing, maybe try making an improved version, and share the improvements. And let us know about it!

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Commodore Datasette Does Its Own Calibration

November 7, 2022 by Jonathan Bennett 41 Comments

Ah, the beloved Commodore 64. The “best-selling computer system of all time”. And hobbyists are keeping the dream alive, still producing software for it today. Which leads us to a problem with using such old equipment. When you get your copy of Petscii Robots on cassette, and try to fastload it, your machine might just consistently fail to load the program. That’s fine, time to pull out the cue-tips and rubbing alcohol, and give the read heads a good cleaning. But what if that doesn’t do the job? You may just have another problem, like tape speed drift.

There are several different ways to measure the current tape speed, to dial it in properly. The best is probably a reference cassette with a known tone. Just connect your frequency counter or digital oscilloscope, and dial in the adjustment pot until your Datasette is producing the expected tone. Oh, you don’t have a frequency counter? Well good news, [Jan Derogee] has a solution for you. See, you already have your Datasette connected to a perfectly serviceable frequency counter — your Commodore computer. He’s put out a free program that counts the pulses coming from the Datasette in a second. So play a reference cassette, run the program, and dial in your Datasette deck. Simple! Stick around after the break for a very tongue-in-cheek demonstration of the problem and solution.

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Rope Core Drum Machine

November 6, 2022 by Jonathan Bennett 7 Comments

One of our favorite musical hackers, [Look Mum No Computer] is getting dangerously close to building a computer. His quest was to create a unique drum machine, inspired by a Soviet auto-dialer that used rope core memory for number storage. Rope memory is the read-only sibling to magnetic core memory, the memory technology used to build some beloved computers back in the 60s and early 70s. Rope core isn’t programmed by magnetizing the ceramic donuts, but by weaving a wire through them. And when [Look Mum] saw the auto-dialer using the technology for a user-programmable interface, naturally, he just had to build a synth sequencer.
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Garage Door Opener Ejection Seat

November 5, 2022 by Jonathan Bennett 16 Comments

[Scott Prints] had a familiar problem. His garage door opener was boring, and rattled around annoyingly in his car’s center console. This was obviously a major issue that needed to be dealt with. His solution was to install an ejector seat. Er, well, an ejector seat button. At least, that’s what it’s labeled. (That’s sure to be a great conversation starter for passengers.)

The end result looks slick and combines several build techniques. He started by taking measurements and 3D-printing a test piece for the center console nook. Turns out, that’s a more complicated shape than it seems. Rather than try to measure the exact angles and radii, Scott turned to the tried-and-true method of fiddling with the parameters and printing a second test. Close enough.

The coolest and most challenging element of the build was engraving and cutting the aluminum plate that forms the visible part of the build. Turns out, the online recommendations for milling aluminum are laughably optimistic when you don’t have an industrial CNC machine. Slower, shallower cuts got the job done, albeit slowly. A red paint-filled marker made the letters pop. The guts of the donor garage door opener are fitted into a 3d-printed shell, and then a Big Red Button threads into the print, holding the whole build together. A bit of solder later, and the project is done. Simple, effective, and very stylish! We approve. Come back after the break for the build video.
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This Week In Security: OpenSSL Fizzle, Java XML, And Nothing As It Seems

November 4, 2022 by Jonathan Bennett 3 Comments

The security world held our collective breaths early this week for the big OpenSSL vulnerability announcement. Turns out it’s two separate issues, both related to punycode handling, and they’ve been downgraded to high severity instead of critical. Punycode, by the way, is the system for using non-ASCII Unicode characters in domain names. The first vulnerability, CVE-2022-3602, is a buffer overflow that writes four arbitrary bytes to the stack. Notably, the vulnerable code is only run after a certificate’s chain is verified. A malicious certificate would need to be either properly signed by a Certificate Authority, or manually trusted without a valid signature.

A couple sources have worked out the details of this vulnerability. It’s an off-by-one error in a loop, where the buffer length is checked earlier in the loop than the length variable is incremented. Because of the logic slip, the loop can potentially run one too many times. That loop processes the Unicode characters, encoded at the end of the punycode string, and injects them in the proper place, sliding the rest of the string over a byte in memory as a result. If the total output length is 513 characters, that’s a single character overflow. A Unicode character takes up four bytes, so there’s your four-byte overflow. Continue reading “This Week In Security: OpenSSL Fizzle, Java XML, And Nothing As It Seems” →

This Week In Security: IOS, OpenSSL, And SQLite

October 28, 2022 by Jonathan Bennett 13 Comments

Earlier this week, a new release of iOS rolled out, fixing a handful of security issues. One in particular noted it “may have been actively exploited”, and was reported anonymously. This usually means that a vulnerability was discovered in the wild, being used as part of an active campaign. The anonymous credit is interesting, too. An educated guess says that this was a rather targeted attack, and the security company that found it doesn’t want to give away too much information.

Of other interest is the GPU-related fix, credited to [Asahi Lina], the VTuber doing work on porting Linux to the Apple M1/M2 platform, and particularly focusing on GPU drivers. She’s an interesting case, and doing some very impressive work. There does remain the unanswered question of how the Linux Kernel will deal with a pull request coming from a pseudonym. Regardless, get your iOS devices updated.

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