Hackaday Prize Entry: Hot Logic

A few weeks ago, [Yann] was dumpster diving and found something of interest. Two vacuum tubes, an ECC83S and an EL84. This was obviously the droppings of a local guitarist, but [Yann] wanted to know if he could build something useful out of them. An amplifier is far too pedestrian, so he settled on a vacuum tube computer.

The normal pentodes and triodes you’ll find in a tube amp require a lot of support components like output transformers, tube sockets, and high voltage power supplies. This was a little too complicated for a tube computer, but after a little bit of searching, [Yann] found a better option for his MINIVAC — subminiature vacuum tubes. These require fewer support components, and can be found for very reasonable prices through the usual component suppliers. His entry for this year’s Hackaday Prize is Hot Logic. It’s a computer — or at least computer components — built out of these tubes.

The tubes in question are a few 1Ж29Б-В and 6Н21Б tubes, a vacuum pentode and dual triode, respectively. Add in a few diodes, and that meets the requirements for being sufficient to build a computer. As a neat little bonus, these tubes have requirements that are very easy to meet. The filament on the 1Ж29Б-В tube only needs 1.2 Volts.

These subminiature tubes are a little underappreciated in the world of audiophililia and DIY electronics. That’s a bit of a shame; these tubes are the most technologically advanced vacuum-based technology ever created. They were the heart and the brains of ballistic missiles, and if you look hard enough you source hundreds of them at very reasonable prices. A vacuum tube computer requires a lot of tubes, and if anyone will be able to build a vacuum tube computer it’s going to be [Yann] and his pile of Soviet surplus.

33 thoughts on “Hackaday Prize Entry: Hot Logic

      1. Agreed. I like the idea of surviving long enough to enjoy it a time or two ;) High volt tubes are none of my business at this point in my tinkering. I like the 12V tubes and great job :)

  1. These are hardly the most advanced tubes ever built. That crown is securely held by the selectron tube from RCA. The originals each store 4096 bits in one tube, and 40 of them were to supply the approximately 5KB for the IAS stored program machine. Unfortunately, they proved hard to mass produce, and by the time RCA came out with a 256 bit version, they had already been replaced by less reliable William’s tube memory, which was then replaced by core. Only one computer, a later clone of the IAS machine ever used selectron tubes as main memory.

    While these might be the tube version of the ICs with 3-5 transistors, the selectron tube is easily comparable to an early RAM chip.

      1. That PDF is very informative, thanks !

        I considered the nuvistor but 1) too expensive on eBay, probably because 2) not crap enough to be sold at $65/100pcs, and 3) it doesn’t “look” like valve/tubes and people would bitch that it isn’t one.

        Conversely, when I used quartz resonators in glas tubes, people wanted to believe it emitted light and heat.
        “The look is the function” and, had I used nuvistors, I would have also lost the other point : it’s not as wasteful, pointless or dangerous.
        You have to admit that a nuvistor is not a “tube”. Despite reaching temperatures of 150-200°C.

  2. How about making integrated vacuum logic? I don’t know the dimensions needed for cold emission (electron tunneling) to replace the (hot) electron gun but if hobbyist level lithography techniques are enough there’s a lot of potential there IMHO.

    If it is possible to do on a reasonable budget it will still require actual vacuum unlike the nanoscale vacuum transistors DARPA etc. have worked on, but there are a number of hobbyists that make traditional valves already.

      1. There were supposed to be circuits like that appearing for military purposes in the 50s before transistors took over. I think we saw some of that tech resurface in VFDs … But would have been cool to see where it would have got to today.

    1. According to wikipedia field effect emission require a field of the order of 1GV/m, IOW with a 1µm gap ~1000V and with a 10nm gap ~100V is required.

      Time to start designing an ALD (=Atomic Layer Deposition) system perhaps? ;P

      1. Correction: 10nm -> ~10V, 100nm -> ~100V.

        Also the effect on voltages to power consumption (P=UI) isn’t directly comparable to semiconductors,e.g. with a good vacuum one can get ballistic conduction quite often even @ 100nm.

  3. Interesting! Looking forward to reading of your work with these tubes.

    I’ve bought several ot these Soviet miniature tubes too, but my intended projects are radio receivers. I’ve already made a decent radio using a larger Soviet surplus tube, but now I want to try to make something smaller.

    The neat thing about tube regenerative receivers is that despite being a nearly 100 year old circuit, a simple tube regenerative reciever with one or two tubes still performs comparably to many modern receivers.

  4. i know regular tubes (67.5v – 337.5v) will eventually be ruined at low anode voltages depending on type… but wouldnt they work “good-enough” for logic even after being “runined” for audio purposes ???

    i mean, ive never run a 300v tube at 12v long enough to find out, but they do work at 12v anode/plate; good enough to light low-efficiency LIMEgreen LED. just remember to keep the grid voltage below anode (i think) execpt in beam-power tubes where it should not be more then a small percent larger then plate/anode

    and the reduced voltage on anode/plate means low output power, but its still okay for logic or LEDs.

    PS: by low anode voltage i mean low plate/anode (B_voltage), im not talking about the filament(A_voltage), that HAS to be full or tube is for sure ruined very quickly

    1. This question can only be answered by characterization …
      I won’t send the damned stuff in space, it will be powered on from time to time (if at all) and longevity is nice but not a requirement for such a WTF exploration. Why do I even bother when I can get a 3K transistors reel for $30 on eBay ?
      Characterisation is half of the project’s “fun” because it shows how practical use is, compared to the cult/myth surrounding it. I’m quite concerned by the low output power they provide, relays are much slower but much more practical (doing relay logic is even more easy than with transistors !). I suppose I can light a recent, high-efficiency LED with a triode output but what about a tiny incandescent lamp that needs 30mA ? The impendances don’t match and it’s not possible to use an impendance matching transformer like in audio amplifiers, that work with AC.

    1. Don’t forget to check for switching frequency tough!

      Nixie supplies come in more flavours than there are colours in a rainbow with each differing in frequency. lower frequency supplies are quite audible!

      Tough i find you can make it work if you implement a RC-Filter or 2. May take some space in the form of a bulky HV capacitor and some calculating the values, but still smaller and WAY cheaper than a huge transformer!

  5. Those tiny Soviet tubes are indeed pretty awesome. I have a nice little set of 6 6h16b for less than a single standard miniature tube (like 12a*7).

    They perform really well for their size and indeed give real nice sound! just know that they aren’t suitable for “starved” designs (driving the tubes with say 12-24v on the plate) due to their bias going negative and can get a tad hot!

  6. I don’t kn if I’m on d right site but I’m going to ask anyway where would I find out what is d value of rapiopon v12 western electric co. In I might hav tex it wrong but where can I find d worth of these vacuum tubes thank you

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