Hand-Made Vacuum Tubes

djmoore writes "Over at Make Magazine, watch this video of a French amateur radio operator making and testing his own vacuum tubes. It looks like he built much of his own equipment as well. The Make poster notes: 'I love the ease with which he performs these rather high-end skills (like glass forming), the gestural flourishes (like it's hand magic), and the Zelig-esque soundtrack.'"

reason

Over at Make Magazine, watch this video of a French amateur radio operator making and testing his own vacuum tubes.

This was covered in Make Magazine, primarily because Nature abhors a vacuum.

Yeah, well

Make will rectify that!

Re:"French amateur radio operator"

Neither Make nor Slashdot have the basic decency to name the man: Claude Paillard.

What is it with acting like foreign nationals are some sort of trained monkey? C'mon folks.

Anyway, here's a direct link to his site so you can skip the non-article at Make. Site includes much information (use the fish as needed), the streaming dailymotion vid, and a download link for those who can't see streams. Enjoy.
http://paillard.claude.free.fr/ [claude.free.fr]

Thanks Claude! That rocks.

thank you

for pointing out the man's website and giving him direct credit. Its sad to see something placed without naming the inventor.

Re:"French amateur radio operator"

take that homebrew computer club! i'll bet none of those guys ever made their own transistors!

Re:"French amateur radio operator"

What is it with acting like foreign nationals are some sort of trained monkey?

French amateur radio operator

Freedom amateur radio operator...
There, fixed it for you.

Re:reason

the article is over 5+ pages with a lot of details on making something (http://www.make-digital.com/make/vol04/?pg=124&pm=2&u1=friend) - while the author didn't post the data sheets he used an analogy and explained it to do the project, that's what most folks want, at least for this type of article - for more details we usually the companion pages on MAKE, the forums and additional articles we refer to. part of a project like this is a little reverse engineering from an amateur who is ok with exploring things too - regardless, sorry we didn't live up to your expectations.

Re:reason

I do hope that your trip is not dicey.

The art of electronics

This guy isn't just a tinkerer, but an artist as well. This kind of thing is an art as much as it is a science.

Re:The art of electronics

Yeah, like Pierre Scerri, who spent 15 years making a scale model of a Ferrari 312. [techeblog.com] Not only did he make the body, he learned to make glass in order to create the headlights, and learned to make rubber to make his own tires. It's almost unbelievable.

Re:The art of electronics

'I can respect having an obsessive hobby. Especially when it produces such spectacular results.'

Though with some people, this sort of thing can get just a bit _too_ obsessive:

http://www.sandia.gov/LabNews/LN02-13-98/cherry_story.html [sandia.gov]

'The switch mechanisms Kaczynski used were hand-made switches that he would spend weeks building...He machined his own screws.'

Re:The art of electronics

He machined his own screws.

Machining screws isn't so bad, but if the some guy starts hand filing and grinding his own screws to a perfect mirror polish, watch out...

Many moons ago I was the "gofer" for our school's one act play. The lead character was going to use a prop broom as a crutch, so the teacher in charge told me to shorten the wooden screw-in handle of the broom. I cut the stick down, and spent the afternoon hand-carving a new screw thread into the bare wood that fit perfectly in the broom head. I was really proud of that carving. But the handle was still a few inches too tall, so the teacher told me to cut it shorter. And this time, he told me to just cut off the plain end. D'oh!

We need this type of thing done in the classrooms

While vacumn tubes are strictly in the realm of hobbyists and zealous audiophiles, nevertheless it is important for teens and young adults to understand where the electronics industry started from. They're already made to study what can argueably be considered useless information, so why not study something that is cool and informative as well? Think of it as shop class for nerds.

Re:We need this type of thing done in the classroo

The purpose of using vacuum tubes in a guitar amp is for the overdrive characteristics. When overdriven, solid state amplification circuitry clips the waveform to the voltage rails, resulting in a harsh sounding distortion due to the dissonant overtones.

A tube amp driven to distortion compresses the waveform rather than hard clipping. This results in a waveform rich in harmonic overtones - the classic distorted guitar sound.

Any person who is not tone deaf can tell the difference between solid state distortion and tube distortion. Please don't compare the basic principles of rock guitar with overpriced audiophile folly.

Semiconductors never could have been made without

vacuum tubes.

Once you get beyond the crude PN junction diode (like a galena crystal), making transistors and such requires ridiculously pure germanium and/or silicon. These materials are purified by a process called "zone refining" which uses induction heating to melt the semiconductor materials at incredibly high temperatures. Induction heating in turn requires many kilowatts of radio frequency power, which is exactly the type of application where vacuum tubes are still widely used even today.

Re:We need this type of thing done in the classroo

You can learn a hell of a lot from vacuum tubes! They are far easier to understand than transistors.

There's a reason why they're called "valves" in the UK. It's like a valve controlling a powerful stream of water; a small change on the valve leads to a very large change of current. That change in current can, in turn, control a much bigger valve that controls an even larger current.

In this case, the "valve" is a control grid (that spiral thing) surrounding the cathode (the thin hot wire in the middle). The big cylinder is the "plate". The cathode itself has a cloud of electrons around it (because it's hot), and a small signal on the grid controls how much of that can scoot across to the plate (which is positively charged due to a power supply putting a strong positive voltage on it). So a weak sine wave signal on the plate will lead to a big sine wave current from the plate.

There, now you know the basics of amplification (although I skipped some details). I couldn't have done it by describing a BJT (transistor), because they're far weirder.

The next logical step...

Perhaps we can use these hand-made tubes to make a new hand-made internets! Think of the possibilities!

Upping the coolness factor

The only thing that would make this cooler is if he made his own Nixie tubes!

I thought there were issues not addressed clearly in the video. First, I thought I learned in college chemistry (now rummaging in decades-old longterm storage media) that one of the big problems was getting a good seal of glass around metal, which wasn't solved until they put together the right glass with the right metal.

Also, aren't the electrodes in a vacuum tube coated with something to prevent early breakdown? And isn't there some chemical you have to put inside the tube to absorb the gas given off when electrons smash into the electrodes? So while this is incredibly neat-looking, I don't think the tubes would last very long...

--Rob

Glass/Metal seals...

If you look closely at the wires he is sealing into the glass "press", you will see a short reddish-brown section. This is most likely "dumet", or copper coated nickel/iron. This material is specially designed to have the same coefficient of thermal expansion as glass, and was used as the sealing material in most receiving tubes. The copper coating forms an oxide layer that dissolves into the glass, creating a vacuum-tight seal.

Before the development of dumet, kovar, and other specialized alloys, the seals in very early tubes were made using platinum wire. Cost considerations brought this to a quick end, as soon as cheaper suitable materials were developed.

The electrodes in later tubes were often coated with various materials to aid heat dissipation or reduce secondary electron emission. Early tubes that were similar in construction to what is being made here generally used plain metal grids and plates.

Most tubes contained a "getter" made of barium or other reactive metal, to adsorb any gas molecules which survived initial pumpdown, or which were liberated from the internal elements during operation.

Re:Getter

He was superheating the entire structure to drive out occluded gases from the metal components. During this operation, the entire tube was surrounded by a coil driven by an induction heater, which was heating the plate and grid red hot, as well. All this takes place while the tube is attached to the vacuum pump, prior to sealoff.

I am not sure what material he was using for his filament wire, but if it was thoriated tungsten, then the "hot shot" cycle also serves to build up a surface layer of thorium oxide on the filament, and reduce it to metallic thorium. Thorium has a much lower work function than pure tungsten, and will emit electrons efficiently at a much lower operating temperature.

Yes, I am a tube geek...:) Years ago, I made a much cruder triode in a peanut butter jar as a HS physics project.

you might have noticed the plate red hot in a coil

"refining" a tube typically meant heating it up in an inductive system to burn out impurities and gas in the tube elements, and filaments may or may not also be heated up at that time. typically were. getters are often "flashed" with a high voltage impressed on them during this period to be sure the impurities are fully absorbed and can't get back into the tube metals and glass spacers.

many getters at the period in which that tube type he's duplicating used phosphorus. not as efficient as aluminum and barium, but easier to flash over. WWI, remember, you couldn't pull much vacuum. the getter had to do the job. so old tubes had funny colors inside from the getter flashover.

State of the Art

Limping through the writeup with what's left of my high school French I get the idea that he's not just making homemade tubes, he's duplicating a particular class of historic tubes which were common around WWI. He's using authentic techniques. These tubes were handmade at great expense because they were used for maritime communication where price was no object, and modern standards of longetivity didn't apply; if such a tube lasted 500 hours it was doing great. Also, some of those tubes had soft vacuum so an imperfect seal wasn't such a big deal.

I do have to say this is one of the most impressive projects of its type I've ever seen; it's clearly a labor of both love and skill.

He not only made the tube,

he also made all the necessary equipment, like vacuum pump. If you are interested in tubes, he says the "musée des arts et métiers" is a reference. This is an engeneering museum in Paris, which has an incredible collection. When I go there, I stay for hours. Do not mistake it with the science, the nature science, or the technology museum (which are also quite interesting).

Vacuum tubes were pretty much ALL hand-made....

, as sophisticated robotics didn't yet exist. The most sophisticated part of tube making, the assembly of the internal components or "mount" was done largely by hand, usually by rows and rows of women (smaller fingers) hunched over microscopes in dust-free rooms.

Once the mounts were assembled and welded onto the stems, the sealing into bulb and pumping down was somewhat automated. Done on a machine called a "sealex", the mounts would be inserted into bulbs, sealed in place, evacuated, heated to activate the cathodes, sealed off, and getters flashed, with each operation taking place at a different "station" on the sealex.

An interesting photo essay on the construction of the famous 300B audio triode is available here:

http://www.westernelectric.com/history/tour01.html [westernelectric.com]

I'm impressed

He actually found a use for those tiny scissors that come with a Swiss Army Knife.