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The thing to have when every other mad scientist on your block is already rocking the Jacob’s ladder. Sure, you have to ignore the fact that it’s loud, clunky, and chock-full of toxic metal, but geez…just look at it. [Thanks, Billy Baque!]


Sean Michael Ragan

Sean Michael Ragan

I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I am a long-time contributor to MAKE magazine and My work has also appeared in ReadyMade, c’t – Magazin für Computertechnik, and The Wall Street Journal.

  • Dave

    One quibble – they are indeed beautiful, and I remember the unearthly glow very well – but they are not “arc” devices. The mercury exists as a tenuous vapor, and the tube (“valve”, if you insist!) works on ion flow, rather than electron flow in a normal vacuum tube. If an arc were to form, there would be essentially a dead sort between anode and cathode, and it wouldn’t function very well as a rectifier (diode)…

  • Sean Michael Ragan

    Wikipedia calls them “arc valves”:

    And I’m not sure I understand the distinction you’re trying to make about what counts as “arc” and what doesn’t. By my understanding, the very definition of an electrical arc involves ion flow: Normally nonconductive media break down, by ionizing, to produce charged particles that permit the flow of charge carriers in a very high EM field.

  • Simon

    The local transport and technology museum (MOTAT) has a tram track that it runs and they use these there. They have several there you can see working (mostly – last time I was there the glass was filthy). You can see the glow change as the trams move up and down the tracks. They definitely call it a mercury arc rectifier.

  • robert scott

    hi all i would like to buy or trade for a working one

  • Nyanman

    Just found this.
    Compared to the older rotary AC/DC converters, Mercury Arc valves are very quiet, very simple, very reliable, very compact, etc.

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