You Can Use A CRT As An Audio Amplifier Tube

July 11, 2024 by Lewin Day 36 Comments

When we talk about audio amplifier tubes, we’re normally talking about the glass little blobby things you might find in a guitar amplifier. We’re not normally talking about big ol’ color CRTs, but apparently they can do the job too. That’s what [Termadnator] is here to show us.

The CRT in question is a 14″ unit from a common garden variety Philips color TV. [Termadnator] pulled out the TV’s original circuitry, and replaced much of it with his own. He had to whip up a high-voltage power supply with a 555 and a laptop power supply, along with a bunch of fake MOSFETs pressed into service. He also had to build his own Leyden jar capacitor, too. The specifics of converting it to audio operation get a bit messy, but fear not—[Termadnator] explains the idea well, and also supplies a schematic. Perhaps the coolest thing, though, is the crazy color pattern that appears on the display when it’s working as an amp.

Sound output isn’t exactly loud, and it’s a little distorted, too. Still, it’s amusing to see an entire TV instead doing the job of a single amplifier tube. Video after the break.

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Custom Microcode Compiler, Made In Google Sheets

July 7, 2024 by Donald Papp 12 Comments

When homebrewing a CPU, one has to deal with microcode. Microcode is the low-level nuts and bolts of how, precisely, a CPU executes instructions (like opcodes) and performs functions such as updating the cycle counter or handling interrupt requests. To make this task easier, [Bob Alexander] created a microcode compiler built in Google Sheets to help with his own homebrew work, but it’s flexible and configurable enough to be useful to others, as well.

A CPU’s microcode usually lives in read-only memory, and writing the microcode is only one step in the journey. [Bob]’s tool compiles his microcode into files that can be burned into memory (multiple EEPROM chips, in [Bob]’s case) or used as a Verilog program in the case of implementing the CPU in an FPGA. It’s configurable enough to be adapted for other homebrew CPU projects, though one would of course have to re-write the microcode portion.

A read-only version of the spreadsheet makes for some fun browsing, and if it piques your interest enough to get a copy of your own complete with the compiler script, you can do that here. It uses Google Sheets, and writes the output files into one’s Google Drive.

This kind of low-level project really highlights the finer points of just how the hard work of digital computing gets done. A good example is the Gigatron which implemented a RISC CPU using only microcode, memory, and logic gates in the late 70s. We’ve even seen custom microcode used to aid complex debugging.

Halfway Between Inspiration And Engineering

July 6, 2024 by Elliot Williams 7 Comments

We see a lot of hacks where the path to success is pretty obvious, if maybe strewn with all sorts of complications, land-mines, and time-sinks. Then we get other hacks that are just totally out-of-the-box. Maybe the work itself isn’t so impressive, or even “correct” by engineering standards, but the inner idea that’s so crazy it just might work shines through.

This week, for instance, we saw an adaptive backlight LED TV modification that no engineer would ever design. Whether it was just the easiest way out, or used up parts on hand, [Mousa] cracked the problem of assigning brightnesses to the LED backlights by taking a tiny screen, playing the same movie on it, pointing it at an array of light sensors, and driving the LEDs inside his big TV off of that. No image processing, no computation, just light hitting LDRs. It’s mad, and it involves many, many wires, but it gets the job done.

Similarly, we saw an answer to the wet-3D-filament problem that’s as simple as it could possibly be: basically a tube with heated, dry air running through it that the filament must pass through on it’s way to the hot end. We’ve seen plenty of engineered solutions to damp filament, ranging from an ounce of prevention in the form of various desiccant storage options, to a pound of cure – putting the spools in the oven to bake out. We’re sure that drying filament inline isn’t the right way to do it, but we’re glad to see it work. The idea is there when you need it.

Not that there’s anything wrong with the engineering mindset. Quite the contrary: most often taking things one reasonable step at a time, quantifying up all the unknowns, and thinking through the path of least resistance gets you to the finish line of your project faster. But we still have to admire the off-the-wall hacks, where the way that makes the most sense isn’t always the most beautiful way to go. It’s a good week on Hackaday when we get both types of projects in even doses.

Cavity Filters, The Black Art You Have A Chance Of Pursuing

July 4, 2024 by Jenny List 12 Comments

A tuned circuit formed by a capacitor and an inductor is a familiar enough circuit, and it’s understood that it will resonate at a particular frequency. As that frequency increases, so the size of the capacitor and inductor decrease, and there comes a point at which they can become the characteristic capacitance and inductance of a transmission line. These tuned circuits can be placed in an enclosure, at which they can be designed for an extremely high Q factor, a measure of quality, and thus a very narrow resonant point. They are frequently used as filters for that reason, and [Fesz] is here with a video explaining some of their operation and configurations.

Some of the mathematics behind RF design can be enough to faze any engineer, but he manages to steer a path away from that rabbit hole and explain cavity filters in a way that’s very accessible. We learn how to look at tuned circuits as transmission lines, and the properties of the various different coupling methods. Above all it reveals that making tuned cavities is within reach.

They’re a little rare these days, but there was a time when almost every TV set contained a set of these cavities which were ready-made for experimentation.

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Retrotechtacular: The Tools And Dies That Made Mass Production Possible

July 3, 2024 by Jenny List 14 Comments

Here at Hackaday we’re suckers for vintage promotional movies, and we’ve brought you quite a few over the years. Their boundless optimism and confidence in whatever product they are advancing is infectious, even though from time to time with hindsight we know that to have been misplaced.

For once though the subject of today’s film isn’t something problematic, instead it’s a thing we still rely on today. Precision manufacturing of almost anything still relies on precision tooling, and the National Tool and Die Manufacturers Association is on hand in the video from 1953 below the break to remind us of the importance of their work.

The products on show all belie the era in which the film was made: a metal desk fan, CRT parts for TVs, car body parts, a flight of what we tentatively identify as Lockheed P-80 Shooting Stars, and a Patton tank. Perhaps for the Hackaday reader the interest increases though when we see the training of an apprentice toolmaker, a young man who is being trained to the highest standards in the use of machine tools. It’s a complaint we’ve heard from some of our industry contacts that it’s rare now to find skills at this level, but we’d be interested to hear views in the comments on the veracity of that claim, or whether in a world of CAD and CNC such a level of skill is still necessary. Either way we’re sure that the insistence on metrology would be just as familiar in a modern machine shop.

A quick web search finds that the National Tool and Die Manufacturers Association no longer exists, instead the search engine recommends the National Tooling And Machining Association. We’re not sure whether this is a successor organisation or a different one, but it definitely represents the same constituency. When the film was made, America was at the peak of its post-war boom, and the apprentice would no doubt have gone on to a successful and pretty lucrative career. We hope his present-day equivalent is as valued.

If you’re of a mind for more industrial process, can we direct you at die casting?

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All About CRTs

June 25, 2024 by Al Williams 76 Comments

For old-timers, CRTs — cathode ray tubes — were fixtures as kids sat in front of TVs watching everything from Howdy Doody to Star Trek. But there’s at least one generation that thinks TVs and computer monitors are flat. If that describes you, you might enjoy [The 8-Bit Guy’s] coverage of how CRTs work in the video below.

CRTs were heavy, took high voltage, and had a dangerous vacuum inside, so we really don’t miss them. The phosphor on the screen had a tendency to “burn in” if you showed the same image over and over. We don’t miss that either.

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The Amstrad E-m@iler, The Right Product With The Wrong Business Model

June 25, 2024 by Jenny List 29 Comments

One of the joys of the UK’s Electromagnetic Field hacker camp lies in the junk table, where trash turns to treasure in the blink of an eye. This year I returned relatively unscathed from my few days rifling through the tables,but I did snag a few pieces. One of them is a wired telephone, which would be a fairly unremarkable find were it not for its flip-up LCD screen and QWERTY keyboard.

My prize is a 2002 Amstrad E-m@iler Plus, one of a series of internet-equipped telephones from the British budget electronics company. The device itself and the story behind it make for a fascinating tale of a dotcom-era Internet flop, and a piece of hardware that could almost tempt today’s hackers.

You’ve Heard Of The Dotcom Boom, But Have You Heard Of The Hardware?

In the late 1990s, everything was about the Internet, but seemingly few outside the kind of people who read Hackaday really understood what it was really about. I’ve written before on these page about how hype blinded the CD-ROM industry to the shortcomings of its technology, but while that had in reality only gripped the publishing business, the Internet hype which followed had everyone in its thrall. You’re probably familiar with the story of the dotcom boom and crash as startup companies raised millions on shaky foundations before folding when they couldn’t deliver, but in parallel with that there was also a parallel world for hardware. The future was going to be connected, but on what and whose hardware would that connection happen? Continue reading “The Amstrad E-m@iler, The Right Product With The Wrong Business Model” →