Making A Solid State 6AK8 Tube

July 22, 2024 by Al Williams 13 Comments

[M Caldeira] had a project in mind: replacing a common vacuum tube with a solid-state equivalent. The tube in question was an EABC80 or 6AK8 triple diode triode. The key was identifying a high-voltage FET and building it, along with some other components, into a tube base to make a plug-in replacement for the tube. You can see a video about the project below.

These tubes are often used as a detector and preamplifier. Removing the detector tube from a working radio, of course, kills the audio. Replacing the tube with a single diode restores the operation of the radio, although at a disadvantage.

From there, he adds more diodes directly into the socket. Of course, diodes don’t amplify, so he had to break out a LND150 MOSFET with a limit of 500 volts across the device. It takes some additional components, and the whole thing fits in a tube base ready for the socket.

Usually, we see people go the other way using tubes instead of transistors in, say, a computer. If you want real hacking, why not make your own tubes?

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Ask Hackaday: Should We Teach BASIC?

July 21, 2024 by Al Williams 183 Comments

Suppose you decide you want to become a novelist. You enroll in the Hackaday Famous Novelists School where your instructor announces that since all truly great novels are written in Russian, our first task will be to learn Russian. You’d probably get up and leave. The truth is, what makes a great (or bad) novel transcends any particular language, and you could make the same argument for programming languages.

Despite the pundits, understanding the basics of how computers work is more important than knowing C, Java, or the language of the week. A recent post by [lackofimagination] proposes that we should teach programming using BASIC. And not a modern whizz-pow BASIC, but old-fashioned regular BASIC as we might have used it in the 1980s.

Certainly, a whole generation of programmers cut their teeth on BASIC. On the other hand, the programming world has changed a lot since then. While you can sort of apply functional and object-oriented techniques to any programming language, it isn’t simple and the details often get in the way of the core ideas.

Still, some things don’t change. The idea of variables, program flow, loops, and arrays all have some parallel in just about anything, so we can see some advantages to starting out simply. After all, you don’t learn to drive by trying it out in the Indy 500, right?

What do you think? If you were teaching programming today, would you start with BASIC? Or with something else? You can modernize a little bit with QB64. Or try EndBasic which just recently had a new release.

How Ten Turn Pots Are Made

July 19, 2024 by Al Williams 5 Comments

It is easy to think of a potentiometer as a simple device, but there are many nuances. For example, some pots are linear — a change of a few degrees at the low end will change the resistance the same amount as the same few degrees at the high end. Others are logarithmic. Changes at one end of the scale are more dramatic than at the other end of the scale. But for very precise use, you often turn to the infamous ten-turn pot. Here, one rotation of the knob is only a tenth of the entire range. [Thomas] shows us what’s inside a typical one in the video below.

When you need a precise measurement, such as in a bridge instrument, these pots are indispensable. [Thomas] had a broken one and took that opportunity to peer inside. The resistor part is a coil of wire wound around the inside of the round body. Unsurprisingly, there are ten turns of wire that make up the coil.

The business end, of course, is in the rotating part attached to the knob. A small shuttle moves up and down the shaft, making contact with the resistance wire and a contact for the wiper. The solution is completely mechanical and dead simple.

As [Thomas] notes, these are usually expensive, but you can — of course — build your own. These are nice for doing fine adjustments with precision power supplies, too.

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A Nostalgic Look At A Kid’s Shortwave Receiver

July 18, 2024 by Al Williams 10 Comments

[Mikrowave1] had a Unelco shortwave receiver as a kid. This was a typical simple radio for the 1960s using germanium and silicon transistors. It also had plug-in coils you had to insert into sockets depending on the frequency band you wanted to receive.

While simple AM radios were all the rage, they didn’t have to operate at higher frequencies. [Mikrowave1] shows some of the design tricks used to allow the radio to operate in the upper part of the spectrum. Otherwise, the radio is the usual superhet design using lower frequency germanium PNP transistors in the IF stage. You get a look inside the radio and a peek at a similar schematic along with notes on where the radio is different.

But how does it work? For an old single-conversion receiver, it works well enough. Of course, when the radio was new, there were many more interesting stations on shortwave. Today, he had to settle for some ham radio stations and CHU, the Canadian time and frequency station.

There were six pairs of coils built on top of tube sockets. The coil was actually more than a coil. There were other components in the case that adjusted other radio parameters based on the frequency.

[Mikrowave1] has been on a toy kick lately, and we’ve enjoyed it. This radio looks simple compared to the Radio Shack one that every kid wanted in the 1970s. Well. Every hacker kid, at least.

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Supercon 2023: Bringing Arcade Classics To New Hardware

July 18, 2024 by Tom Nardi 8 Comments

The processing power of modern game consoles is absolutely staggering when compared to the coin-op arcade machines of the early 1980s. Packed with terabytes of internal storage and gigabytes of RAM, there’s hardly a comparison to make with the Z80 cabinets that ran classics like Pac-Man. But despite being designed to pump out lifelike 4K imagery without breaking a virtual sweat, occasionally even these cutting-edge consoles are tasked with running one of those iconic early games like Dig Dug or Pole Position. Nostalgia is a hell of a drug…

As long as there are still demand for these genre-defining games, developers will have to keep figuring out ways to bring them to newer — and vastly more complex — systems. Which is precisely the topic of Bob Hickman’s 2023 Supercon talk, The Bits and Bytes of Bringing Arcade Classics to Game Consoles. Having spent decades as a professional game developer, he’s got plenty of experience with the unique constraints presented by both consoles and handhelds, and what it takes to get old code running on new silicon.

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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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Why The 555 Is Not A Timer, But Can Be One

July 11, 2024 by Maya Posch 31 Comments

Although commonly referred to as a ‘timer IC’, the venerable NE555 and derivatives are in fact not timer ICs. This perhaps controversial statement is the open door that gets kicked in by [PKAE Electronics] over at YouTube, as he explains with excellent diagrams and simulations how exactly these ICs work, and what it takes to make it actually do timer things. For anyone who has ever used one of these chips there is probably nothing too mind-blowing, but it’s an infinitely better way to wrap your way around an NE555 and kin than a datasheet.

At its core, the 555 contains three 5 kOhm resistors as a voltage divider, which has been incorrectly postulated to be the source of the chip’s name. This voltage divider controls two comparators, which in turn control an SR flipflop. These comparators are used for the voltage trigger and threshold inputs, which in turn toggle the flipflop, respectively setting and resetting it. This by itself just means that the 555 can be used as a threshold detector, with settable control voltage. How a 555 becomes a timer is when the discharge, trigger and threshold pins are combined with external resistors and a capacitor, which creates a smooth square wave on the 555’s output pin.

There are many ways to make basic components into an oscillator of some type, but the 555 is a great choice when you want something more refined that doesn’t involve using an entire MCU. That said, there’s far more that the 555 can be used for, as [PKAE] alludes to, and we hope that he makes more excellent videos on these applications.

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