classic hacks

2656 Articles

Low-Voltage Tube Amp Is Great For Beginners

November 3, 2014 by 39 Comments

If you ever wanted to build your own tube amplifier but you were intimidated by working with high voltages, [Marcel]’s low-voltage tube amp design might spark your interest. The design operates with a B+ (plate) voltage of only 40v, making it less intimidating and dangerous than many other amps that operate over 300V. It’s also incredibly easy to build—the whole design uses only 11 components.

The amplifier is designed around the ECL82 tube, which includes both a triode and a pentode in one package. The ECL82 is practically an amplifier in a tube: it was designed for low-cost electronics like record players that needed to be as simple as possible. The triode in the ECL82 is used as a pre-amplifier for the incoming signal. The pentode is controlled with the pre-amplified signal and acts as a power amplifier.

[Marcel]’s amplifier also uses a PY88 tube rectifier instead of semiconductor diodes, making it an entirely silicon-free design. Although [Marcel] hasn’t posted up detailed build instructions yet, his simple schematic should be all you need to get started. If you want some more background information about tube amps but you don’t know where to start, check out our post on basic tube amp design from earlier this year.

Flaming Jack-o’-lanterns Light Up The Night

October 30, 2014 by 14 Comments

[misterdob] wanted to spice up his Halloween decor, so he built these flaming concrete jack -o’-lanterns to decorate his walkway. He started with the classic plastic jack-o’-lanterns that trick-or-treaters have been using to collect candy for years. [misterdob] filled the plastic pumpkins halfway with concrete mix, then dropped in metal coffee cans. He then filled the pumpkins up to the top with concrete, shaking them up a bit to avoid air pockets.

Once the concrete had set, [misterdob] cut away the plastic revealing nearly perfect concrete duplicates. He used acid stain to color his creations – though it looks like he missed a spot or two.

We have to disagree with [misterdob’s] choice of fuels. In fact, we think he was out of his gourd when he picked gasoline for his flaming pumpkins. Seriously though, gasoline is a horrible choice for a fire pot like this for a multitude of reasons. Gas has a particularly foul odor and its fumes are explosive. If a Halloween prankster were to try kicking one of the pumpkins over, not only would they have a broken foot, they’d also be covered in burning gas.

Thankfully, the folks on [misterdob’s] Reddit thread had better fuel suggestions – citronella torch cans with lamp oil and wicks, kerosene, or gel fuel would be better suited for these hot pumpkins.

If you still don’t believe how dangerous gas and its fumes can be, check out this video of a bonfire gone wrong (language warning).

A Graphics Card For A Homebrew Computer

October 30, 2014 by 49 Comments

One of [aepharta]’s ‘before I die’ projects is a homebrew computer. Not just any computer, mind you, but a fabulous Z80 machine, complete with video out. HDMI and DisplayPort would require far too much of this tiny, 80s-era computer, and it’s getting hard to buy a composite monitor. This meant it was time to build a VGA video card from some parts salvaged from old equipment.

When it comes to ancient computers, VGA has fairly demanding requirements; the slowest standard pixel clock is 25.175 MHz, an order of magnitude faster than the CPU clock in early 80s computers. Memory is also an issue, with a 640×480, 4-color image requiring 153600 bytes, or about a quarter of the 640k ‘that should be enough for anybody.’

To cut down on the memory requirements and make everything a nice round in base-2 numbers, [aepharta] decided on a resolution of 512×384. This means about 100k of memory would be required when using 16 colors, and only about 24 kB for monochrome.

The circuit was built from some old programmable logic ICs pulled from a Cisco router. The circuit could have been built from discrete logic chips, but this was much, much simpler. Wiring everything up, [aepharta] got the timing right and was eventually able to put an image on a screen.

After a few minutes, though, the image started wobbling. [aepharta] put his finger on one of the GALs and noticed it was exceptionally hot. A heatsink stopped the wobbling for a few minutes, and a fan stopped it completely. Yes, it’s a 1980s-era graphics card that requires a fan. The card draws about 3W, or about two percent of a modern, high-end graphics card.

A Proof Of Concept Flash Cart For The WonderSwan

October 28, 2014 by 22 Comments

Unless you’ve been to Japan or are fairly deep into the retro game collecting, you’ve probably never heard of the WonderSwan. It’s a handheld console, released after the Game Boy Color was beginning to show its age, and a bit before the introduction of the Game Boy Advance. It sold rather well in the only country it was released in, the game library is somewhat impressive, and there are quite a few homebrew games. Actually running these homebrew games is a challenge, though: each WonderSwan has a memory controller that maps the game ROM into the CPU’s memory. Without knowing how this controller chip works, the only way to run a homebrew cartridge is to turn on the machine with a real cart, go to the system menu, and swap the carts out. It turns out there’s a better solution, that includes programming CPLDs and looking at the output of a logic analyzer.

The first step towards [Godzil]’s efforts to create a Flash cart for the WonderSwan is to figure out the pinout of the cartridge connector – something that isn’t well documented for a system without a homebrew hardware scene. This was done in the usual way; with a lot of ribbon cable and patience This only provided an incomplete picture of how the WonderSwan interfaced with its carts, but after digging up an official development board, [Godzil] was able to make sense of all the signals.

After building a breakout board for the cartridge port, [Godzil] connected a DE0 Nano FPGA board and looked at all the signals. With just a little bit of VHDL, the memory controller could be reverse engineered and reimplemented. [Godzil] has his proof of concept working – video below – and the next part of his project will be to turn this into a proper Flash cart.

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Restoring A PDP-10 Console Panel

October 28, 2014 by 27 Comments

The PDP-10 was one of the first computers [Jörg] had gotten his hands on, and there are very, very few people that can deny the beauty of a panel full of buttons, LEDs, dials, and analog meters. When one of the front panels for a PDP-10 showed up on eBay, [Jörg] couldn’t resist; a purchase that would lead him towards repairing this classic console and making it functional again with a BeagleBone.

The console [Jörg] picked up is old enough to have voted for more than one Bush administration, and over the years a lot of grime has covered the beautiful acrylic panels. After washing the panel in a bathtub, [Jörg] found the dried panel actually looked worse, like an old, damaged oil painting. This was fixed by carefully scraping off the clear coat over two weeks; an important lesson in preserving these old machines. They’re literally falling apart, even the ones in museums.

With the front panel cleaned, [Jörg] turned his attention to the guts of this panel. The panel was wired up for LEDs, and each of the tiny flashlight bulbs in the pushbuttons were replaced. The panel was then connected to a BlinkenBone with a ton of wiring, and the SIMH simulator installed. That turns this console into a complete, working PDP-10, without sucking down kilowatts of power and heating up the room

This isn’t the first time we’ve seen [Jörg] with a BeagleBone and some old DEC equipment; earlier he connected the front panel of a PDP-11 variant to one of these adapters running the same software.

Mehdi wth his homemade taser

[Mehdi’s] Shocking Stun Gun Tutorial

October 25, 2014 by 25 Comments

[Mehdi Sadaghdar] never lets little things like fire, shocks, or singed fingers get in the way of his projects.  His latest is a tutorial on making a simple electroshock device. A stun weapon creates a very high voltage, and is used in law enforcement to temporarily disable a person. [Mehdi] stresses repeatedly to not use this on anyone. If you do, he won’t like you anymore. Of course, if you’ve seen any of his previous videos, you know he’ll shock himself and set something on fire before the project is complete.

To create his stunner, [Mehdi] used a car ignition to produce a high voltage. The igniton coil, which is a specialized transformer, allowed him to generate the >10000V output needed for the stunner. The coil has a 60:1 ratio and is powered by a 12V DC supply. Since a coil is a short at DC, the system only creates a high voltage pulse when power is disconnected. However, the pulse was too short to create a satisfying arc. [Mehdi] added a capacitor, creating an LC circuit that oscillates as the charge decays, creating a nicer spark. He then used an RC circuit and a relay to create a simple oscillating switch. For the finishing touch, he created a spark gap on the secondary of the transformer with two nails. In typical [Mehdi] fashion, he nearly fried his digital caliper in the process.

The end result is a nice spark that warms the cockles of [Mehdi’s] fibrillating heart. We commend him for being such a brave masochist in the name of science.  Check out his tutorial after the break!

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A Complete C64 System, Emulated On An STM32

October 23, 2014 by 43 Comments

The Commodore 64 is the worlds bestselling computer, and we’re pretty sure most programmers and engineers above a certain age owe at least some of their career to this brown/beige keyboard that’s also a computer. These engineers are all grown up now, and it’s about time for a few remakes. [Jeri Ellisworth] owes her success to her version, there are innumerable pieces of the C64 circuit floating around for various microcontrollers, and now [Mathias] has emulated everything (except the SID, that’s still black magic) in a single ARM microcontroller.

On the project page, [Mathais] goes over the capabilities of his board. It uses the STM32F4, overclocked to 235 MHz. There’s a display controller for a 7″ 800×480 TFT, and 4GB of memory for a library of C64 games. Without the display, the entire project is just a bit bigger than a business card. With the display, it’s effectively a C64 tablet, keyboard not included.

This is a direct emulation of the C64, down to individual opcodes in the 6510 CPU of the original. Everything in the original system is emulated, from the VIC, CIAs and VIAs, serial ports, and even the CPU of the 1541 disk drive. The only thing not emulated is the SID chip. That cherished chip sits on a ZIF socket for the amazement of onlookers.

You can check out some images of the build here, or the video demo below.

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