Flipped Transformer Powers Budget-Friendly Vacuum Tube Amp

November 7, 2023 by Dan Maloney 31 Comments

If you’ve ever wondered why something like a radio or a TV could command a hefty fraction of a family’s yearly income back in the day, a likely culprit is the collection of power transformers needed to run all those hungry, hungry tubes. Now fast-forward a half-century or more, and affordable, good-quality power transformers are still a problem, and often where modern retro projects go to die. Luckily, [Terry] at D-Lab Electronics has a few suggestions on budget-friendly transformers, and even shows off a nice three-tube audio amp using them.

The reason transformers were and still are expensive has a lot to do with materials. To build a transformer with enough oomph to run everything takes a lot of iron and copper, the latter of which is notoriously expensive these days. There’s also the problem of market demand; with most modern electronics favoring switched-mode power supplies, there’s just not a huge market for these big lunkers anymore, making for a supply and demand equation that’s not in the hobbyist’s favor.

Rather than shelling out $70 or more for something like a Hammond 269EX, [Terry]’s suggestion is to modify an isolation transformer, specifically the Triad N-68X. The transformer has a primary designed for either 120 or 230 volts, and a secondary that delivers 115 volts. Turn that around, though, and you can get 230 volts out from the typical North American mains supply — good enough for the plate supply on the little amp shown. That leaves the problem of powering the heaters for the tubes, which is usually the job of a second 6- or 12-volt winding on a power transformer. Luckily, the surplus market has a lot of little 6.3-volt transformers available on the cheap, so that shouldn’t be a problem.

We have to say that the amp [Terry] put these transformers to work in sounds pretty amazing — not a hint of hum. Good work, we say, but we hope he has a plan in case the vacuum tube shortage gets any worse.

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A Simple And Effective 3D Filament Splicer

October 27, 2023 by Jenny List 29 Comments

There are times in every 3D print enthusiast’s life when it would be convenient to join two pieces of filament. The problem with simply melting them together is that the resulting join has a blob of plastic surrounding it which has difficulty making it through the printer’s internals. [Pete Prodoehl] has a solution, in the form of a well-executed splicing jig that’s sure to leave a join which will glide through your printer.

The trick lies in performing the join in a space only marginally wider than the filament width, in the case of 1.75 mm filament a short piece of 1.775 mm PTFE tube encased in a 3D printed clamp. A 90-degree cut piece of filament is fed through the tube and heated with a candle, then withdrawn into the tube where a 45-degree cut piece is pushed in to fuse with it. The result is a seamless and bulge-less join, that can pass through an extruder without issue and print continuous pieces from different filaments.

It’s a very effective technique, but it’s not the only one we’ve seen over the years. This one by comparison heats the filament in a hair straightener, and relies on gently pulling the join apart as it solidifies in order to reduce the bulge.

Clever Mechanism Powers This All-Mechanical Filament Respooler

March 25, 2023 by Dan Maloney 12 Comments

No matter how far down the 3D printing rabbit hole we descend, chances are pretty good that most of us won’t ever need to move filament from one spool to another. But even so, you’ve got to respect this purely mechanical filament respooler design, and you may want to build one for yourself just because.

We were tipped off to [Miklos Kiszely]’s respooler via the very enthusiastic video below from [Bryan Vines] at the BV3D YouTube channel. He explains the need for transferring filament to another spool as stemming from the switch by some filament manufacturers to cardboard spools for environmental reasons. Sadly, these spools tend to shed fibrous debris that can clog mechanisms; transferring filament to a plastic spool can help mitigate that problem.

The engineering that [Miklos] put into his respooler design is pretty amazing. Bearings excepted, the whole thing is 3D printed. A transmission made of herringbone gears powers both the take-up spool and the filament guide, which moves the incoming filament across the width of the spool for even layers. The mechanism to do this is fascinating, consisting of a sector gear with racks on either side. The racks are alternately engaged by the sector gear, moving a PTFE filament guide tube back and forth to create even layers on the takeup spool. Genius!

Hats off to [Miklos] on this clever design, and for the extremely detailed instructions for printing and building one of your own. Even if you don’t have the cardboard problem, maybe this would help if you buy filament on really big spools and need to rewind for printing. Continue reading “Clever Mechanism Powers This All-Mechanical Filament Respooler” →

3D Printer Spool Roller Is Built For Giant Spools Of Filament

January 27, 2023 by Lewin Day 15 Comments

Most 3D printers come with a pretty basic filament holder — often little more than a bar to hang the spool on. [Ivan Miranda]’s 3D printers run bigger spools than most, though, so he had to craft an altogether more serious solution.

Unlike most of [Ivan]’s creations, the spool holder isn’t actually 3D printed. For this job, he turned to a laser cutter instead, cutting the parts out of 5 mm plywood. A handful of layers of wood bolt together to form the frame. The frame holds several bearings for the outer rims of the spool itself to ride on, allowing it to spin freely as the extruder tugs on the filament. Reducing the rolling resistance of the spool is key when working with such large, heavy spools, and reduces the chances of the filament not feeding properly.

It’s a tidy example of a tool built quickly and easily using a laser cutter. It pays to remember that while 3D printers are great, a laser cutter can often turn out parts in a short fraction of the time.

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Make Your Own Color Gradient 3D Printing Filament

September 30, 2022 by Lewin Day 1 Comment

Color gradient filament is fun stuff to play with. It lets you make 3D prints that slowly fade from one color to another along the Z-axis. [David Gozzard] wanted to do some printing with this effect, and learned how to make his own filament to do the job.

[David] intended to 3D print a spectrogram of a gravity wave, and wanted the graph to go from blue to yellow. Only having a single-color printer, he needed color shift filament, but couldn’t find any blue-to-yellow filament online.

The resulting color-shifting print looks great, demonstrating the value of the technique.

Thus, he elected to create it himself. He started by creating a spiral model in Fusion 360, with a hexagonal cross-section and slowly tapering off to a point. Slicing and printing this in blue results in a filament that slowly fades down to a point. The opposite shape can then be printed in yellow, tapering from a point up to a full-sized filament. The trick is to print one shape, then the other, by mashing the G-code together and changing the filament from blue to yellow along the way. The result is the blue and yellow plastic gets printed together into a single filament that gradually changes from one to the other.

Notably, the filament is smaller than the original filaments used to create it, so it’s necessary to run slightly different settings when using it. [David] has shared the models on Thingiverse for those eager to recreate the technique at home. His resulting gravity wave print is impressive, demonstrating that this technique works well!

We’ve seen similar different techniques used for creating multi-color filaments before, too. Video after the break.

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PET Bottles Diligently Turned Into Filament

August 25, 2022 by Bryan Cockfield 21 Comments

While the price of 3D printers has come down quite a lot in the past few years, filament continues to be rather pricey especially for those doing a lot of printing. This has led to some people looking to alternatives for standard filament, including recycling various forms of plastic. We’ve seen plenty of builds using various materials, but none so far have had this level of quality control in the final project.

What sets this machine apart from others is that it’s built around an Arduino Nano and includes controls that allow the user to fine-tune a PID controller during the conversion of the recycled plastic into filament. Different plastic bottles have different material qualities, so once the machine is started it can be adjusted to ensure that the filament produced has the exact specifications for the printer. The PCB is available for download, and the only thing that needs to be done by hand besides feeding the machine to start it is to cut the plastic into strips for the starter spool. There is also a separate 3D printed tool available to make this task easy, though.

Not only could this project save printing costs, but it also keeps harmful plastics out of landfills and other environments. Recycling plastic tends to be quite difficult since producing new plastic is incredibly cheap, and the recycled material can’t be used as often as other materials such as aluminum. But there are still plenty of people out there trying to reuse as much of it as they can.

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3D Print Your Own Multi-Color Filament

July 6, 2022 by Donald Papp 11 Comments

Interested in experimenting with your own multi-color filament? [Turbo_SunShine] says to just print your own, and experiment away! Now, if you’re thinking that 3D printing some filament sounds inefficient at best (and a gimmick at worst) you’re not alone. But there’s at least one use case that it makes sense for, and maybe others as well.

Printing with bi-color filament results in an object whose color depends on viewing angle, and part geometry.

There is such a thing as bi-color filament (like MatterHackers Quantum PLA) which can be thought of as filament that is split down the center into two different colors. Printing with such filament can result in some trippy visuals, like objects whose color depends in part on the angle from which they are viewed. Of course, for best results it makes sense to purchase a factory-made spool, but for light experimenting, it’s entirely possible to 3D print your own bi-color filament. Back when [Turbo_SunShine] first shared his results, this kind of stuff wasn’t available off the shelf like it is today, but the technique can still make sense in cases where buying a whole spool isn’t called for.

Here is how it works: the 3D model for filament is a spiral that is the right diameter for filament, printed as a solid object. The cross-section of this printed “filament” is a hexagon rather than a circle, which helps get consistent results. To make bi-color filament, one simply prints the first half of the object in one color, then performs a color change, and finishes the print with a second color. End result? A short coil of printed “filament”, in two colors, that is similar enough to the normal thing to be fed right back into the printer that created it. This gallery of photos from [_Icarus] showcases the kind of results that are possible.

What do you think? Is 3D printing filament mainly an exercise in inefficiency, or is it a clever leveraging of a printer’s capabilities? You be the judge, but it’s pretty clear that some interesting results can be had from the process. Take a few minutes to check out the video (embedded below) for some additional background.

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