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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Reviewing Nuclear Accidents: Separating Fact From Fiction

July 22, 2024 by Maya Posch 93 Comments

Few types of accidents speak as much to the imagination as those involving nuclear fission. From the unimaginable horrors of the nuclear bombs on Nagasaki and Hiroshima, to the fever-pitch reporting about the accidents at Three Mile Island, Chernobyl and Fukushima, all of these have resulted in many descriptions and visualizations which are merely imaginative flights of fancy, with no connection to physical reality. Due to radiation being invisible with the naked eye and the interpretation of radiation measurements in popular media generally restricted to the harrowing noise from a Geiger counter, the reality of nuclear power accidents in said media has become diluted and often replaced with half-truths and outright lies that feed strongly into fear, uncertainty, and doubt.

Why is it that people are drawn more to nuclear accidents than a disaster like that at Bhopal? What is it that makes the one nuclear bomb on Hiroshima so much more interesting than the firebombing of Tokyo or the flattening of Dresden? Why do we fear nuclear power more than dam failures and the heavy toll of air pollution? If we honestly look at nuclear accidents, it’s clear that invariably the panic afterwards did more damage than the event itself. One might postulate that this is partially due to the sensationalist vibe created around these events, and largely due to a poorly informed public when it comes to topics like nuclear fission and radiation. A situation which is worsened by harmful government policies pertaining to things like disaster response, often inspired by scientifically discredited theories like the Linear No-Threshold (LNT) model which killed so many in the USSR and Japan.

In light of a likely restart of Unit 1 of the Three Mile Island nuclear plant in the near future, it might behoove us to wonder what we might learn from the world’s worst commercial nuclear power disasters. All from the difficult perspective of a world where ideology and hidden agendas do not play a role, as we ask ourselves whether we really should fear the atom.

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FauxTRS Is Definitely Not A Trash 80

July 22, 2024 by Jenny List 12 Comments

Among the 8-bit home micro boom from the late 1970s through early 1980s, the introduction to computing for many wasn’t a pricey Apple or Commodore, instead it was the slightly lower budget machine from Radio Shack. The TRS-80 series of computers live on and have a loyal following among retro computing enthusiasts. But like all such machines the original hardware is harder to find in 2024, so how about the TRS-80 experience without the failing vintage parts? The FauxTRS from [Jpasqua] is just that, the feel of a Model 3 or Model 4, powered by a Raspberry Pi.

In a sense then, this is a very well-designed case for a Raspberry Pi that looks a lot like the Tandy of old. With a modern LCD and keyboard it could just as easily be a normal desktop machine, but when the emulator fires up it does indeed look very much like a small version of the real thing. You can download the STL files from Printables, and for the cost of a few extra parts you can have one too.

Alternatively, if a faux TRS doesn’t do it for you, there’s always the chance of making a more real one.

An AVO 8 Teardown

July 22, 2024 by Al Williams 7 Comments

AVO meters — literally amp, volt, ohm meters — are not very common in North America but were staples in the UK. [TheHWcave] found an AVO 8 that is probably from the 1950s or 1960s and wanted to get it working. You can see the project in the video below.

These are very different from the standard analog meters many of us grew up with. [TheHWcave] shows how the dual range knobs work together to set the measurement. There are three separate ohm settings, and each one has its own zero pot. We were surprised that the meter didn’t have a parallax-correcting mirror.

Other than dirty switch contacts, the voltage measurements still worked. After cleaning the contacts, most of the ranges worked well, although there were still some issues. Some of the resistor ranges were not working, either. Inside the case were an old D cell and a square battery, a B121 15 V battery. Replacing the 15 V battery with a bench supply made things better.

Some plugins are available to allow the meter to read low resistance or high currents. We thought using the soldering gun as a current source was clever. Once he gets it working, he opens the box around the 14:30 mark.

The inside was all hand-wiring and power resistors. Of course, there are also a ton of contacts for the switches. So it isn’t just an electrical design, but a mechanical one, too. The electrical design is also interesting, and an analysis of it winds the video down.

[Jenny List] has a soft spot for these meters, too. Why use an old meter? If you have to ask…

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Coax Stub Filters Demystified

July 21, 2024 by Dan Maloney 9 Comments

Unless you hold a First Degree RF Wizard rating, chances are good that coax stubs seem a bit baffling to you. They look for all the world like short circuits or open circuits, and yet work their magic and act to match feedline impedances or even as bandpass filters. Pretty interesting behavior from a little piece of coaxial cable.

If you’ve ever wondered how stub filters do their thing, [Fesz] has you covered. His latest video concentrates on practical filters made from quarter-wavelength and half-wavelength stubs. Starting with LTspice simulations, he walks through the different behaviors of open-circuit and short-circuit stubs, as well as what happens when multiple stubs are added to the same feedline. He also covers a nifty online calculator that makes it easy to come up with stub lengths based on things like the velocity factor and characteristic impedance of the coax.

It’s never just about simulations with [Fesz], though, so he presents a real-world stub filter for FM broadcast signals on the 2-meter amateur radio band. The final design required multiple stubs to get 30 dB of attenuation from 88 MHz to 108 MHz, and the filter seemed fairly sensitive to the physical position of the stubs relative to each other. Also, the filter needed a little LC matching circuit to move the passband frequency to the center of the 2-meter band. All the details are in the video below.

It’s pretty cool to see what can be accomplished with just a couple of offcuts of coax. Plus, getting some of the theory behind those funny little features on PCBs that handle microwave frequencies is a nice bonus. This microwave frequency doubler is a nice example of what stubs can do.

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CeraMetal Lets You Print Metal, Cheaply And Easily

July 21, 2024 by Elliot Williams 27 Comments

3D printing metal has been somewhat of a holy grail for the last decade in the hobby 3DP scene. We’ve seen a number of solutions, including using expensive filaments that incorporate metal into the usual plastic. In parallel, we’ve seen ceramic printers, and paste printers in general, coming into their own. What if you combined the two?

You’d get [Leah Buechly] et al’s CeraMetal process, which is the cheapest and most straightforward metal printing method we’ve seen to date. It all starts off with a custom bronze metal clay, made up of 100 g bronze powder, 0.17 g methyl cellulose, 0.33 g xanthan gum, and 9 g water. The water is fine-tuned to get the right consistency, and then it’s extruded and sintered.

The printer in question is an off-the-shelf ceramic printer that appears to use a pressurized clay feed into an auger, and prints on a linen bed. [Leah] had to write a custom slicer firmware that essentially runs in vase mode but incorporates infill as well, because the stop-start of normal slicers wreaked havoc with clay printing.

The part is then buried in activated carbon for support, and fired in a kiln. The result is a 3D printed bronze part on the cheap; the material cost is essentially just the cost of the metal powder and your effort.

We had never heard of metal clay before, but apparently jewelers have been using it for metals other than just bronze. The Metal Clay Academy, from the references section of the paper, is an amazing resource if you want to recreate this at home.

Paste printers are sounding more and more interesting. Obvious applications include printing chocolate and printing pancakes, but now that we’re talking metal parts with reasonably consistent shrinkage, they’ve got our attention.

Hackaday Links: July 21, 2024

July 21, 2024 by Dan Maloney 20 Comments

When monitors around the world display a “Blue Screen of Death” and you know it’s probably your fault, it’s got to be a terrible, horrible, no good, very bad day at work. That’s likely the situation inside CrowdStrike this weekend, as engineers at the cybersecurity provider struggle to recover from an update rollout that went very, very badly indeed. The rollout, which affected enterprise-level Windows 10 and 11 hosts running their flagship Falcon Sensor product, resulted in machines going into a boot loop or just dropping into restore mode, leaving hapless millions to stare at the dreaded BSOD screen on everything from POS terminals to transit ticketing systems.

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