The Art of Vacuum Tube Fabrication

Vacuum tubes fueled a technological revolution. They made the amplification of signs that a reality for transatlantic phone cables (and transcontinental ones also ), they performed logic for ancient computers, and they delivered the warm fuzzy sound for high fidelity audio. However, they were labor intensive to produce, and fragile, therefore semiconductors came along and replaced tubes in almost every program. But obviously tubes are still with us and a few tube applications continue to be crucial — that you ’ll find these used in high-power RF and you will find even satellites which rely on klystrons. So there continue to be experts in tube fabrication around, also Charles Alexanian is one of these. His newly-published talk at the 2018 Hackaday Supercon (found below) is a whirlwind tour of what goes on creating a vacuum tube.

The process of building your own vacuum tube isn’t hard, but it’s not a stroll in the park. The difficulty comes in the sheer number of processes, and the tricks of the trade found at each step. Charles’ methaphor is that in case you build one tube at a time every thing is similar to learning how to ride a bicycle , but should you assemble many you get into the swing of things and it move a lot better. His conversation is a short overview of everything, but should you want to drill down he wrote an superb post that goes further in thickness .

In the functioning parts of each tube are the precision parts: that the grid (or grids). For the tube to work well these must be correctly produced which can be done with photolithography, but Charles generally employs a winding procedure between a lathe. After winding, the grid is stretched to straighten the nickel cable, then cut to length. Other components such as the plate have been stamped using an arbor press and also easy kinds he fabricates for your goal.

Tube being examined for leaks

Two glass parts are utilized, the dome itself, and feedthrough stalks which have a cable for every contribute passing through a glass disk. The parts are spot welded to the interior section of the feedthrough stem, then the glass is fused together, again using a lathe. It heads to a pumping station to evacuate the air from the tube, and is ultimately tested for leaks using a handheld Tesla coil (see, we knew those weren’t only toys).

Charles suggested his Supercon look for a opportunity to fabricate tubes on-site. We loved the concept, however, the amount of equipment needed is somewhat restrictive (annealing ovens, vacuum cupboards, torches for sealing, and also the need for 220v, plus space for it all). That’s too bad because we had been really hoping to see that the Jolly Wrencher in Nixie-tube form — incidentally, Charles states Nixes are easy to make compared to amplifiers and switches. He also cites that the vast majority of your time is invested “washing” parts to eliminate impurities. Fair enough, that part sounds boring, but we aspire to survive it at some point in the future since vacuum tube manufacture demos feel like a Hackaday event!

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