Home Brew Vacuum Tubes Are Easier Than You Think

It all began with a cheap Chinese rotary vane vacuum pump and a desire to learn the witchcraft of DIY vacuum tubes. It ended with a string of successes – a working vacuum chamber, light bulbs, glow tubes, diodes, and eventually this homebrew power triode and the audio amplifier built around it.

[Simplifier]’s workshop seems like a pretty cool place. It must have a bit of an early 20th-century vibe, like the shop that [John Fleming] used for his early work on vacuum tubes. Glass work, metal work, electronics – looks like [Simplifier] has a little bit of everything going on. True to his handle, once [Simplifier] had a cheap but effective vacuum rig he started with the easiest projects – incandescent and gas discharge lamps. Satisfied that he could make solid electrical and physical connections and evacuate the tubes, he moved on to diodes and eventually triodes. The quality of the tubes is pretty impressive – stray gasses are removed with a bake-out oven and induction-heated titanium getters. And the performance is pretty solid, as the video below reveals.

Very impressive overall, and it’s not just the fact that he’s building tubes from scratch – we’ve seen that before. What shines here is that specialized equipment is not needed to make working and reliable tubes – just a MAPP torch, simple hand tools, and a low-end vacuum rig. Anybody could – and probably should – give this a try.

53 thoughts on “Home Brew Vacuum Tubes Are Easier Than You Think

    1. Perhaps he can take that into consideration if he decides to mass produce them. For now I am very impress to see someone who probably wasn’t even from the valve era reproduce such old (ancient?) technology. I like re-making old computers so he has far exceeded my skill set.

      1. No need to mass produce anything…
        An annealing oven is very nice to have if you do any kind of useful glass work, old-school chemists that made their own glassware knew that very well…
        You can get by with a MAPP torch even for complicated apparatus, but it’s very likely to shatter from internal stress upon cooldown, which is a damn shame…it usually takes several hours in the oven to make nice stable glassware.

        I myself still hope to one day get to the point where I can grow my own halide scintillator crystals, a process which suffers from similar problems (very sensitive to the cooling rate, tens of °C per hour is the max or they crack).

        1. MAPP gas hasn’t been produced since 2008. What you’re buying now is “MAP-Pro” and the flame temp is only 3730F compared to propane at 3600F for a price 3x that of propane. Also, using either with oxygen it’s still smarter to stick with propane (Oxy/propane 5000F and Oxy/Map-Pro 5390F).

          1. The differences between “real” MAPP and propane have never been very large when burning in air. However a lot of people that have propane torches _also_ have MAPP (or pseduo-MAPP as you correctly point out) torches claiming that the later transfers heat to the joints faster, don’t know it that is true or not.
            Even if the difference is small the availability of MAPP burners and gas bottles makes them attractive to a large group of people, including me.

  1. I can’t believe no one has posted this link. Sometimes I’ll play this just because its relaxing. Its people like this who give me hope that we will survive after the next “Armageddon” ;-) WOW!!!

    Hand Made Vacuum Tubes by Claude Paillard
    https://www.youtube.com/watch?v=EzyXMEpq4qw

    When I was teaching I would show my students this video and use it try and make the point that the wonderful thing about computers and electronics is the nothing is impossible or out of your reach. The answers are there if you care to dig deep enough. Don’t be afraid. Its not magic and fairy dust making all this technology work. Don’t have the software you need? Write it. Don’t have the specific piece of hardware you need? Build it.
    It wasn’t often but when the “light came on” in a students eyes and they realized “Wow. So that’s how this stuff works?!? I want to lean more!” it was so worth it!

    1. I came to post this too, though playback has been disabled on external sites. While I appreciate the “you can do anything” sediment, I also try to temper it with a degree of realism. Yes, many of these things are all possible but they all take time, trials and resources, even assuming they are within the grasp of the people undertaking them. Even Claude Paillard did not learn this whole workflow or build these overnight.

      https://www.youtube.com/watch?v=gl-QMuUQhVM
      This one (half) video might work?

      1. >>While I appreciate the “you can do anything” sediment, I also try to temper it with a degree of realism.
        I agree with you but how many times do we see TODAY that people are just stumped over the littlest things. If my sentiment is “over achieving” its nothing more than to TRY and balance out all the “blank stares” I see with people today dealing with today’s technology.
        And lets be honest. If someone IS truly interested today the answers are SO MUCH easier to come by than it was 20 years ago.

    2. That is why I still have an entire encyclopedia set from the 70’s. You could build a CRT with the info. You could manufacturer the phosphors as well. It’s as if someone printed Wikipedia……

  2. Reliable? I doubt it. A rotary vacuum pump is no where near a good enough vacuum even with a proper getter. Titanium as a getter is not nearly good enough, it primarily wants to react with oxygen which leaves a lot of nitrogen in there. That is just not a good enough vacuum for long term use.

    You can find used diffusion pumps and turbos all over eBay. A small diff pump can be had for $100, though you will be fighting the fusor crowd for them. I have even picked up small Leybold TMP50 turbos for $100 ea. The drives were another $100 or so.

        1. 2mm gives a mean free path of 0.5 hPa, which is only medium vacuum, reachable with a single stage rotary pump.
          A TurboMP is not something made for home use, too much stored energy, these thing have to be bolted down.
          But why not looking at a diy TSP (Titanium sublimation pump) or a diy getter pump?

          1. For proper operation of a vacuum tube you need to be in the 10^-5 torr range, at least.

            I actually have quite a few turbos at home. One on my mass spec RGA (Pfeiffer 71l/s), put one on my SEM (Varian 350l/s), one on the little carbon coater I just build (Leybold 50l/s), another leybold for the RGA on my big vacuum system which has a big Seiko 2000l/s. I am also looking at putting a leybold 700l/s on the smaller vacuum system I have.

            Yes, if the big mag lev Seiko locked up it would be pretty, it would probably rip the pump and valve right of the bottom of the baseplate. But so could a lot of the other stuff I have going wrong really quickly. It’s a calculated risk, I have seen many crashed turbos and it really does not happen that often. You usually have to do something pretty stupid to crash one.

          2. You could easily do a Ti-Sub but you really need to start at a decent high vacuum with these like you do with ion pumps which often have a ti-sub combined with them. So either way you are still going to need a turbo or DP to get down to the start pressure of the ion pump, which can be a pain to start.

            One possibility would be a cryoabsorbtion pump. They cool a stainless chamber holding zeolite with liquid nitrogen to get down to pretty high vacuums. They are good for evacuating small closed spaces, one place I took some glassblowing classes at was using them to evacuate tubes for NMR machines. Only bad thing about these is they need a supply of LN2 and they have a short run until they need to be warmed up an regenerated.

            Third option is a cryopump. Probably the hardiest of pumps but really expensive, even used.

    1. The fact that these tubes work at all is impressive though. Perhaps if he were to flush wth pure oxygen and use a better getter then the reliability would be improved.

      As for diffusion and turbo pumps why not do a write up on them here? What sort of set up would one need to
      get a suitably hard vacuum at a resonable price?

      1. Im not sure how many would be really interested if I blathered on about turbos and stuff. Vacuum tech is very neat and fun but so expensive. Materials matter and some things you just cant get away with cheap.

        Putting pure O2 in there would not be a great idea. At roughing pump pressure probably nothing would happen but you never want to pump oxygen with a standard mineral oil filled pump, big fire potential. You need a fomblin filled pump for that.

      1. But the way he is doing it, not so much. You can use sublimated Ti at very high vacuum to finish a vacuum but at roughing pump range of vacuum you are not going to get much. Plus he is oxidizing his plate which creates an insulating layer which is not really what you want in a vacuum tube. I really have no idea why he is using titanium to begin with.

        You can get standard barium getters online, I saw someone selling them once. With his induction heater he could easily flash them. Though I am betting the getter material will just turn white pretty much immediately.

        1. A regular barium getter would likely handle the gas load in his tubes without trouble. Commercial vacuum tubes were often only pumped down to the 1e-2 to 1 torr range before the getter was fired, due to the short pumping time on the sealex machines used and the limited conductance of the evacuation stem. More info can be found in the excellent book “Vacuum tube design” by RCA, which is freely available online.

          1. I just looked though Materials of High Vacuum Technology and they talk about the sealex machines too. They say generic filament lamps are brought down to -2 and and vacuum tubes down to -3, FWIW.

  3. I was daydreaming about making a vacuum tube from a mason jar. I don’t know why, it just seemed like fun. I don’t even know what I’d use a vacuum tube for given my lack of knowledge in electroncs

    But now maybe I’ll give my idea a shot, just for sh!t$ and grins.

  4. I’ve always wondered about getters. All of the previous articles I’ve seen about home-made vacuum tubes and Nixies have used getters scavenged from dead vacuum tubes. It’s interesting that Simplifier has managed to use titanium wire for this. I had wondered if this would be possible/effective.

    1. In the way that he has, not really. You need surface area and a wire is not going to cut it. you could run current through the wire and heat it to a point where it starts sublimating like in a ti-sub pump but they need to be activated at a much higher vacuum.

      I once saw someone online selling getters, I cant find it anymore. You could also cut up neon sign electrodes, the inside of the electrodes is coated with a getter material that is activated when the tube is being processed.

  5. look up glasslinger on youtube for tube manufacturing magic. and dont get distracted from his appearance (or his disastrous cam) :) i recommend starting on his first vid

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