VFD Display Becomes An Amplifier

November 9, 2013 by Brian Benchoff 15 Comments

Born well into the transistor era of the late 80s, [Fernando] missed out on all the fun you can have with high voltage and vacuum tubes. He wanted to experience this very cool tech, but since you won’t find a tube checker down at the five and dime anymore, where exactly do you get a vacuum tube to play around with? [Fernando]’s solution was to rip apart the vacuum fluorescent display from an old radio (Google Translate) and use that as a triode.

Inside every VFD is a filament, grid, and cathode – three simple elements also found in the triodes of just about every tube amp ever made. By applying a small voltage to the filament, a larger voltage to the cathode, and sending an audio signal to the grid, this triode amplifies the electrical signal coming from a stereo or guitar.

[Fernando] built his circuit on a breadboard, and with a little tweaking managed to get a fairly respectable amount of gain from parts salvaged from a radio. While using VFDs as amplifiers is nothing new – we’ve seen it a few times before, tube builds are always great to see, and bodged up electronics even more so.

A New Old Lathe For Your Hackerspace Or Garage

November 8, 2013 by Jeremy Cook 51 Comments

3D printers, or even small CNC routers may seem like relatively easy machine tools to obtain for your hackerspace or garage. They are both very useful, but at some point you may want to start working with round parts (or convert square-ish items into round parts). For this, there is no better tool than a lathe. You can buy a small and relatively cheap lathe off of any number of distributors, but what if you were to get a good deal on a larger lathe? Where would you even start?

In my case, I was offered a lathe by a shop that no longer had a use for it. Weighing in at 800 pounds and using 3 phase power, this South Bend Lathe might have been obtained economically, but getting it running in my garage seemed like it would be a real challenge. It definitely was, but there are a few mistakes that I’ve made that hopefully you can avoid.

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The Tiniest Video Game

November 7, 2013 by Brian Benchoff 13 Comments

As we read [Adam]’s writeup for an extremely tiny video game system through coke bottle glasses, we’re reminded of the countless times we were told that sitting, ‘too close to the Nintendo’ would ruin our eyes. We’ll happily dismiss any article from a medical journal that says there was any truth to that statement, but [Adam]’s tiny video game system will most certainly hurt your eyes.

A few years ago, Atari sold keychain-sized joysticks that contained classics such as Pong, Breakout, Centipede, and Asteroids. [Adam] apparently ran into a cache of these cool classic baubles and immediately thought of turning them into a stand-alone video game system.

For the display, [Adam] used a CRT module from an old Sony Handicam. These modules had the right connections – power, ground, and composite video input – to connect directly to the Atari keychain games. The result is a video game that’s even smaller than a postage stamp. The picture above shows the tiny CRT next to a 25mm postage stamp; it’s small by any measure.

Deconstructing Apollo Flight Hardware

November 1, 2013 by Brian Benchoff 17 Comments

[Fran] has been researching the Saturn V Launch Vehicle Digital Computer – the computer that flew all the Apollo flights into orbit and onwards towards the moon – for a while now. Even though she’s prodded parts of the LVDC with x-rays and multimeters, this is the first time she’s committed to a little destructive testing.

After [Fran] took a flight-ready LVDC spare to the dentist’s office for x-raying and did an amazing amount of research on this artifact from the digital past, there was only so much she could learn without prying apart a few of these small, strange chip packages. Not wanting to destroy her vintage LVDC board, she somehow found another LVDC board for destructive reverse engineering.

This new circuit board was a bit different from the piece in her collection. Instead of the chip leads being soldered, these were welded on, much to the chagrin of [Fran] and her desoldering attempts. After removing one of these chips from the board, she discovered they were potted making any visual inspection a little difficult.

While [Fran]’s attempts at reverse engineering the computer for a Saturn V were a bit unsuccessful, we’ve got to hand it to her for getting this far; it’s very, very likely the tech behind the LVDC was descended from ICBMs and would thus be classified. Documenting the other computer used in every Apollo launch is an impressive feat on its own, and reverse engineering it from actual hardware, well, we can’t think of anything cooler.

An Overly-Complicated Logic Chip Clock

October 29, 2013 by Brian Benchoff 27 Comments

When a normal alarm clock just won’t do, the only option is to build your own, entirely out of discrete logic chips. [jvok] built this alarm clock for last year’s 7400 Logic Competition. In a desire to go against the grain a little bit, [jvok] decided to use 4000-series logic chips. It was allowed under the rules, and the result is a wonderful example of what can be done without a microcontroller.

Most clock projects we’ve seen use a single button to increase each digit. [jvok] wanted to do something unique, so he is able to set his clock with a ‘mode’ button that allows him to independently set the hours, minutes, and seconds. He’s only ever seen this method of setting a clock’s time used with microcontroller-based projects, and translating even that simple code into pure circuitry is quite impressive.

This clock also includes an alarm function, set by a bunch of DIP switches in binary coded decimal. It’s a great piece of work, and deserving of much more attention than it received during the Open Logic Competition.

A Twitter Connected Mechanical Calculator

October 26, 2013 by Eric Evenchick 11 Comments

Two students at the University of Bristol wanted to create a computer to demonstrate how ALUs work. The result is the TwitALU, a Twitter connected mechanical calculator.

The device uses a custom 7400 series ALU based on the famous MOS 6502 processor. Instead of doing the calculations on a silicon die, the ALU drives mechanical relays. This produces a nice clicky-clacky sound as the calculation is computed.

To start a calculation, you tweet @twittithmetic with your input. A Raspberry Pi is used to load the instructions into the ALU. Once the computation is done, it’s tweeted back to you and displayed on the Nixie tube display. It’s not efficient, or fast, but it does the job of demonstrating the inner workings of the device while doing simple math.

The device’s schematics are all available on the website, and are helpful for understanding how a simple ALU works. After the break, check out a quick clip of the TwitALU in action.

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Making 128MB SIMMs From Junk

October 25, 2013 by Brian Benchoff 25 Comments

simm

Working for a tech repair/recycling center, [Jax] has access to a ton of cool hardware. Most of it is junk, but that’s just the way he likes it. Among his better finds in the depths of a tech treasure trove is a huge antistatic bag of 64 MB 72 pin SIMMs. These were the standard RAM form factor for just about everything in the 90s, and while 64 MB is a huge amount of RAM for the time, they’re still a bit away from the 72 pin max of 128 MB.

After inspecting these sticks, [Jax] noticed something odd. Each side had pads for memory chips, but only one side was populated. Given the rarity of 128 MB sticks of RAM, [Jax] decided he would have a go at adding 64 Megs of RAM to these chips by desoldering one stick and sticking it on the back of another.

These new 128 MB SIMMs made their way into a Macintosh Quadra 605 for testing. While the 64 MB chips worked fine, the new 128 MB chips threw a chime of death. Something was terribly wrong.

While investigating, [Jax] couldn’t find any bridged solder joints, and everything looked okay. Heat is a wonderful test of what went wrong, and with the SIMM connected to a power source, he found all of the newly transplanted chips were hot. Because the chips on back side of the SIMMs were meant to be installed upside down, [Jax] had inadvertently connected the ground to power and power to ground.

Fixing his mistake on a new SIMM, [Jax] popped it in his old Mac and tried booting with these SIMMs again. There wasn’t a chime of death, but booting with these chips took a very long time. This was actually just the Mac checking all the RAM, which was successfully addressed once [Jax] finally booted his OS.