tubes

36 Articles

Build A High Voltage Supply For Vacuum Tube Work

November 25, 2025 by 8 Comments

If you work on simple digital projects, just about any bench supply will offer the voltage and current you’re looking for. However, if you’re working with valves, you’ll often find yourself needing much higher voltages that can be tricky to source. [Chappy Happy] has shared a design for a simple HV power supply that should prove useful to vacuum tube enthusiasts.

The build is fairly basic in nature, lacing together some commonly available parts to generate the necessary voltages for working with common vacuum tubes from a 12 volt DC input. Inside the supply is a UC3843A DC boost converter, set up to output high voltage up to around 300 volts DC, with a ripple filter added for good measure. The output can be adjusted with a knob, with a voltmeter on the front panel. There’s also a 12-volt output, and a LM2596 step down converter to produce 6.3 volts for the filament supply. The whole project is built in an old Heathkit project box, and he demonstrates the supply with a simple single-tube amplifier.

If you find yourself regularly whipping up tube circuits, you might like to have something like this on your workbench. Or, you might even consider cooking up your own tubes from scratch if you’re more adventurous like that. Video after the break.

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Tech In Plain Sight: Pneumatic Tubes

November 17, 2025 by 43 Comments

Today, if you can find a pneumatic tube system at all, it is likely at a bank drive-through. A conversation in the Hackaday bunker revealed something a bit surprising. Apparently, in some parts of the United States, these have totally disappeared. In other areas, they are not as prevalent as they once were, but are still hanging in there. If you haven’t seen one, the idea is simple: you put things like money or documents into a capsule, put the capsule in a tube, and push a button. Compressed air shoots the capsule to the other end of the tube, where someone can reverse the process to send you something back.

These used to be a common sight in large offices and department stores that needed to send original documents around, and you still see them in some other odd places, like hospitals or pharmacy drive-throughs, where they may move drugs or lab samples, as well as documents. In Munich, for example, a hospital has a system with 200 stations and 1,300 capsules,  also known as carriers. Another medical center in Rotterdam moves 400 carriers an hour through a 16-kilometer network of tubes. However, most systems are much smaller, but they still work on the same principle.

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2025 One-Hertz Challenge: A Clock Sans Silicon

July 26, 2025 by 12 Comments

Just about every electronic device has some silicon semiconductors inside these days—from transistors to diodes to integrated circuits. [Charles] is trying to build a “No-Silicon digital clock” that used none of these parts. It looks like [Charles] is on the way to success, but one might like to point out an amusing technicality. Let’s dive in to the clock!

Instead of silicon semiconductors, [Charles] is attempting to build a digital clock using valves (aka tubes). More specifically, his design relies on seven dekatrons, which are the basic counting elements of the clock. By supplying the right voltages to the various cathodes of the dekatrons, they can be made to step through ten (or sometimes twelve) stable states, used as simple memory elements which can be used as the basis for a timepiece. [Charles] will set up the first dekatron to divide down mains frequency by 5 or 6 to get down to 10 Hz, depending on whether the supply is 50 Hz or 60 Hz. The next dekatron will step down 10 times to 1 Hz, to measure seconds. The next two will divide by ten and six to count minutes, while a further two will divide the same way to create an impulse per hour. A final dekatron will divide by 12 to count the hours in a day.

Naturally, time will be displayed on Nixies. While silicon semiconductors are verboten, [Charles] is also considering the use of some germanium parts to keep the total tube count down when it comes to supporting hardware. Also, [Charles] may wish to avoid silicon, but here’s the thing about tubes. They use glass housings, and glass is made of silicon.

Cheeky technicalities aside, it’s a great project that promises to create a very interesting clock indeed. Progress is already steaming along and we can’t wait to see the finished product. We’ve seen dekatrons put to good use before, too. If you’re cooking up your own practical projects with mid-century hardware, don’t hesitate to let us know!

2025 Hackaday One Hertz Challenge

A Vintage ‘Scope Comes Back To Life

June 4, 2025 by 3 Comments

We’re suckers for a vintage electronic teardown here at Hackaday, and thus it’s pleasing to see [Thomas Scherrer OZ2CPU] with a 1962 AEG oscilloscope on his bench. It’s definitely seen better days, and is a single-trace 10 MHz unit of the type you might have seen in a typical general purpose electronics lab back in the day.

Pulling the cover off, and as expected there’s a row of tubes each side of the centrally mounted CRT. No printed circuits in sight, and no transistors either, though the rectifiers are selenium parts. After a clean-up it’s time to look at the tubes, and they show the metallic deposits characteristic of long operation. We’re more used to that from older televisions than test equipment,

Gently bringing the power up it looks promising, but there’s a purple glow from one of the PCL82 triode-pentodes. Replacing that and a double-triode results in a ‘scope that surprisingly, is working. It was evidently a high quality device in the first place, with components capable of lasting for over six decades.

We’ve seen more from his bench involving tubes, including this device using a magic-eye tube as the heavy lifter.

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Dismanteled Hallicrafters radio on workbench

Shortwave Resurrection: A Sticky Switch Fix On A Hallicrafters

March 4, 2025 by 10 Comments

Shortwave radio has a charm all its own: part history, part mystery, and a whole lot of tech nostalgia. The Hallicrafters S-53A is a prime example of mid-century engineering, but when you get your hands on one, chances are it won’t be in mint condition. Which was exactly the case for this restoration project by [Ken’s Lab], where the biggest challenge wasn’t fried capacitors or burned-out tubes, but a stubborn band selector switch that refused to budge.

What made it come to this point? The answer is: time, oxidation, and old-school metal tolerances. Instead of forcing it (and risking a very bad day), [Ken]’s repair involved careful disassembly, a strategic application of lubricant, and a bit of patience. As the switch started to free up, another pleasant surprise emerged: all the tubes were original Hallicrafters stock. A rare find, and a solid reason to get this radio working without unnecessary modifications. Because some day, owning a shortwave radio could be a good decision.

Once powered up, the receiver sprang to life, picking up shortwave stations loud and clear. Hallicrafters’ legendary durability proved itself once before, in this fix that we covered last year. It’s a reminder that sometimes, the best repairs aren’t about drastic changes, but small, well-placed fixes.

What golden oldie did you manage to fix up?

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Convert A Cheap Tube Preamp Into A Headphone Amp With Jenny

February 27, 2025 by 21 Comments

Big-name tube amplifiers often don’t come cheap. Being the preserve of dedicated audiophiles, those delicate hi-fis put their glass components on show to tell you just how pricy they really ought to be. If you just want to dip your toe in the tube world, though, there’s a cheaper and more accessible way to get started. [Jenny List] shows us the way with her neat headphone amp build.

The build starts with an off-the-shelf preamp kit based around two common 6J1 tubes. These Chinese pentode valves come cheap and you can usually get yours hands on this kit for $10 or so. You can use the kit as-is if you just want a pre-amp, but it’s not suitable for headphone use out of the box due to its high-impedance output. That’s where [Jenny] steps in.

You can turn these kits into a pleasing headphone amp with the addition of a few choice components. As per the schematic on Github, a cheap transformer and a handful of passives will get it in the “good enough” range to work. The transformer isn’t perfect, and bass response is a compromise, but it’s a place to start your tinkering journey. Future work from [Jenny] will demonstrate using a MOSFET follower to achieve much the same result.

We’ve seen a great number of headphone amplifiers over the years, including one particularly attractive resin-encased example. Video after the break.

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Retro Computer Goes Back To The 1950s

December 6, 2024 by 24 Comments

When thinking of retrocomputing, many of us will imagine machines such as the Commodore 64 or Apple II. These computers were very popular and have plenty of parts and documentation available. Fewer will go back to the Intel 8008 or even 4004 era which were the first integrated circuit chips commercially available. But before even those transistor-based computers is a retrocomputing era rarely touched on: the era of programmable vacuum tube machines. [Mike] has gone back to the 1950s with this computer which uses vacuum tubes instead of transistors.

The computer has an eight-bit architecture and features most of the components of any modern transistor-based computer of similar computational ability. Memory, I/O, an arithmetic logic unit including a carry bit that allows it to do 16-bit arithmetic, are all implemented using 6N3P dual triode tubes that date to the 50s and 60s and would have been used in similar computers like the IBM 700. All of this drives a flight simulator program or a Fibonacci number generator, demonstrating its general purpose computing capabilities.

Of course, tubes were generally phased out in favor of transistors largely due to their power and space requirements; [Mike] needs a stepladder to maintain this computer as well as around ten minutes each time he starts it up to allow the tubes to warm up, with each module needing over three amps of current each. It’s a hugely impressive build and we’d recommend checking out the video linked below to get more details on its operation. If you’re looking for something a little more accessible to get into the world of vacuum tubes, this single-board tube computer fits the bill.

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