If you want to develop your own vacuum tubes, whether amplifying, Nixie or cathode-ray, you’re going to requirement a vacuum. It’s in the name, after all. For a few thousand bucks, you can most likely pick up a utilized turbo-molecular pump. however exactly how did they make high vacuums back in the day? exactly how did Edison evacuate his light bulbs?
Strangely enough, you might do worse than turn to YouTube for the answer: [Cody] demonstrates building a Sprengel vacuum pump (video embedded below). As tipster [BrightBlueJim] composed us, this job has everything: high vacuum, home-made torch glassware, as well as big quantities of toxic heavy metals. (Somehow [Jim] missed out on the high-voltage from the static electrical energy produced by moving mercury down glass tubes for days on end.)
The pump itself is extremely simple. drops of mercury catch bubbles of air from the vessel to be evacuated as well as ultimately all that’s left is vacuum, at least up until the mercury starts boiling. [Cody] even experiments with cooling the mercury in liquid nitrogen to lower its vapor pressure as well as get an even much better vacuum. It appears like it succeeded, however with his rudimentary measurement method we can’t be sure.
Anyway, if you’ve got a few dollar’s worth of glass tubing, a few kilograms of mercury, a lot more than a few hours to wait, as well as the muscles to lift the mercury as much as the top of the tube, you can develop yourself a vacuum pump that’s completely appropriate for making light bulbs or Nixie tubes. [BrightBlueJim] suggests updating this job from mercury to something like gallium that’s less toxic however still truly dense. We like that idea.
So if you’ve looked on in envy as others have made their own tubes, even going so far as to develop their own total amplifiers, you now have one fewer excuse.