[Glasslinger] Builds Tiny Tubes

In the early days of transistors, RCA and GE were battling against silicon with ever smaller vacuum tubes. These tubes – Nuvistors, Compactrons, and some extremely small JAN triodes were some of the tiniest tubes to ever be created. [glasslinger], YouTube’s expert on DIY valves, is pretty close to beating the tiniest tubes that were ever manufactured. He’s created a miniature diode and triode that are about 1/4″ in diameter and 1″ long.

The most difficult part of making a vacuum tube is getting a perfect glass seal around the pins. For this, [glasslinger] is using very fine tungsten wire and glass beads. A bead is placed around each wire, mounted in a stand, and melted together with a torch.

A diode is simple as far as tubes go, requiring only a filament between two pins. [glasslinger] is just stringing a fine piece of wire between two pins and welding them on with a miniature spot welder. After that, it’s just an issue of melting a 1/4″ glass tube to the base of the tube, putting it under vacuum overnight, and sealing it shut.

29 thoughts on “[Glasslinger] Builds Tiny Tubes

  1. “A diode is simple as far as tubes go, requiring only a filament between two pins.”

    It needs an anode too. The filament is eated to produce free electrons and the anode when at positive voltage attracts thoses electrons producing current. But when the anode is at negative voltage it repulse the electrons and there no current.

    1. While the article may say a diode only needs two pins with a filament, glasslinger does indeed use three pins: two with a coated filament between them, and the third with a plate attached.

      I normally expect a diode to have four pins, separating the heating filament from the cathode, but this one seems to work combining the filament and cathode.

      He also makes a triode with four pins. Unfortunately, he forgot to turn the camera on for the testing.

    1. Vacuum tubes needs near perfect vaccuum. It takes time to evacuate the residual pressure. They needs near perfect vaccum because they works with balistics electrons. One don’t wan’t electrons that shuttle from the cathode (filament) to the anode collides with remaining gaz molecules in their travel. When the tube is gassy one can see a glow within the tube because the electrons colliding with gaz molecules ionize them like neon in the a neon tube.

      1. Right but a “normal” single stage vacuum chamber cannot ever achieve a perfect vacuum. You need a different type of vacuum pump. Leaving it for months would never produce a “perfect” vacuum. It also wasn’t clear if the vacuum pump was left running or not?

        1. I’ve watched a few of glasslinger’s videos. He doesn’t use just a single stage pump. He pumps the tube down with a diffusion pump and also heats the electrodes with an induction heater to cook out the parts as much as possible. In another of the videos with larger tubes he puts an oven around the tube and bakes it out overnight.

      2. The vacuum needed depends on the size of the tube, because of the mean free path of the rest gas. If the void is smaller than the MFP the (rest) molecules stay on the wall of the vessel. On the other side, old big CRT TV’s did have a very low pressure.

        Tubes of this size could even be made without a second stage pump.

    2. In a vacuum the parts inside the tube will start to release impurity molecules which then become gas reducing the vacuum. Keeping the vacuum going removes those molecules until there is little left to be released. That’s also why he “bakes” it, heating the filament while the vacuum is going.

  2. These are tiny tubes burt not record-breakers. Acorn tubes had larger envelopes but much smaller internals for UHF operation, and I have several parts drawers full of 611x series tubes about the size of the one glassslinger made, but which were mass-manufactured and used exensively in the 1950’s and 60’s.

  3. Somewhere out there is video of the manufacturing line for the next size down that Sylvania probably couldn’t talk about in 1949 — the tubes for proximity fuzes. The lines were apparently working into the 70s, and it was amazing to watch the machines just assemble all the bits, shove them into a blank envelope on a carousel, heat, suck, crimp about as fast as you can read this. Rated for shock loads somewhere north of 50,000g, prototypes tested by walloping them with a sledgehammer. (I tried a search, but someone else’s fu is likely better than mine.)

    1. Really? How many time in the video are the guy’s fingers near them? You can’t approximate the size by comparison with those or anything else in the background? Do you really need the exact size anyway? Are you already working on building a little minature radio chassis to be filled the minute his Kickstarter goes live? Sorry to burst your bubble, I don’t think he is going to do that.

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