Ready For The Rapture: This Wind-Up Cassette Player Can Play Anywhere

As useful as electronics are, the need to have some source of power for them can be a bit of an issue, especially for small, portable devices. One of the most low-tech but universally applicable source is human mechanical power, as demonstrated by the rugged 1980s-era Messenger II tape player in a recent [TechMoan] video. Without beating around the bush, this is indeed a device created by an evangelical organization (GRN) that missionaries would take with them to wherever their mission took them. Naturally this put the availability of power from a wall outlet in question, especially in the 1980s when this tape player was produced.

Inside of the GRC Messenger II tape player, with the generator and transformer visible. (Credit: TechMoan)
Inside of the GRC Messenger II tape player, with the generator and transformer visible. (Credit: TechMoan)

Per the specifications for the device, it uses about 1.2 Watt at full power, with said power coming from a 6 VDC barrel jack input (AC adapter or 4 D-cell battery pack), an AC adapter, or from the hard to miss crank handle. This crank handle connects to a set of gears that drive a generator via a belt, though with no buffering in terms of a spring, capacitor or the like. On the same specifications page for the device you can find the service manual (also on, which includes full schematics. In the service manual on page 19 you can see the main schematics, including how the 6 VDC, transformer and generator inputs are handled.

Internally, the circuitry operates off a 5 V rail (after diode drop of the approximately 6 VDC input), with playback and other operations disabled once the input voltage drops below a certain point. Which can happen when the batteries run low, or your cranking arm gets tired after at most a few minutes. Fortunately, the playback speed is regulated so that cranking speed (above a certain RPM) is always sufficient to get decent sounding mono audio output.

Although the crank handle is noted by [TechMoan] as being easy enough to handle, it’s also incredibly tiring so that you can only use it for short sections. For a proper doomsday device, it might be advisable to use something like a pedal-based generator as one’s leg muscles are much better at duration trials, such as pedaling through the entirety of Queen’s Bohemian Rhapsody.

35 thoughts on “Ready For The Rapture: This Wind-Up Cassette Player Can Play Anywhere

    1. Depends if you’re pre or post millennial (or a rare amillennial) – and what your take is on Kirk Cameron!
      Jokes aside, I think these guys came to my church back in the day with pictures of Papuan villagers taking turns cranking this thing listening to Billy Graham tapes.

    2. I think the idea would be that in this silly scenario all the holy US christian… people, would all be gone and then there would be not enough qualified people to keep the powerplants running, and hence the power would cut out.
      Incidentally, I think that rapture nonsense is only a thing in the US right? I don’t think I’ve seen it being a thing anywhere else.

      1. The rapture mainly a big thing in the US (and I think by extension Latin America). I think it’s fair to say most christians in the UK are amillenial, (roughly…) believing that the passages in question about the tribulations and 1000year reign are a symbolic way of describing the entire time between Jesus’ ascension and his return. I *think* most Europeans also would be amillenial.

        I’m not sure what views are common in Africa or Asia.

          1. Not really. Biblical eschatology is confusing, and evidence for a “rapture” is just as sparse and flimsy as for any other interpretation. A strict and literal interpretation of the Bible does not mean belief in a rapture.

          2. > A strict and literal interpretation of the Bible does not mean belief in a rapture.

            Well, it couldn’t anymore, since the whole thing should have happened a thousand years ago.

          3. I’m not allowed to quote 1 Timothy 2:12.

            Especially not an older translation. The newer ones like to leave ‘and she should shutteth her mouth and fix him a sandwich’ out entirely.

            Like ‘slave’ became ‘servant’, translators are liars.

          4. Are you saying that nobody took the Bible seriously until the 1830’s, when the concept of the Rapture emerged? Or that everyone until then, everyone outside of North American Evangelicals just didn’t understand it? Theology is a complicated, many-faceted discipline, and “taking the Bible seriously” is not something you can put on a 0-100 scale.

          5. Everybody who claims to believe in the bible is “just moving goalposts.”

            You’d think since it is (supposedly) the infallible, perfect word of god there’d be no trouble understanding it. God’s word says “X,” you do “X.”

            It ain’t so, though.
            All the folks who claim to live by the bible pick and choose. Not merely between old and new testamant, but just in everything. They just pick the bits they like most or were raised to respect most. Nobody, but nobody, follows it all.

            The simple reason is that it contradicts itself all over the place. It’s a mass of confused and confusing crap.

            The best thing to do with it is to ignore it and the religions that go with it.

          6. nn:
            North american evangelicals are the best argument for keeping the bible in Latin/Greek/Hebrew/Aramaic and burning translators at the stake.

            They are as dumb as Marxists.

    3. A big part of the end of the world that is taught in the Bible is a one world unity. I believe there will be electricity and communications during this time (at least for most of it), since that is the only way to control a global population.

    4. In those times one Cannot buy sell or trade without the mark of the beast. My studies into finances remind me that I currently pay for electricity. Hence the need of a manual powered tape player to an future unmarked christian who will be experiencing the tribulations. That is if you believe in post tribulation rapture. But if you think you will be scooped up before all the action then I pray the best for you and hope your correct. God bless you have a beautiful day.

  1. Was at least hoping for a spring and clockwork, to drive the mechanical cassette parts, plus gen for amp.

    This just bad generator hot glued to cheap cassette player.
    Why not generator, battery, usb, flash and speaker?
    Why tape?

    Why tagged ‘wind-up’ if no spring?

    Spring powered mechanical audio amp from cassette head signal…that would be a hack…Spinning wheel, jeweled pivots, something and a cone?..Include a single tube? Too easy.

  2. This reminds me of the original plans to make the OLPC laptop powerable via crank. Now I feel a tiny bit sad. Maybe this highlight will inspire someone to try pairing one of the ultra-low-power computing options with a clockwork power system to realize the dream.

  3. That big of a clockwork mechanism would have actually cost something, and it would have been quite heavy. A wall clock spring has an energy density of about 300 Watt-seconds per kg, and you need about 3600 Watt-seconds to run the tape player for the duration of the tape – assuming you don’t lose much energy in the mechanism or the generator.

          1. Later Walkman models would run about 9 hours on a standard AA battery, so that’s roughly 1000 Watt-seconds per hour, but that was driving headphones instead of a loudspeaker. The size of the clock spring would still have been quite massive.

  4. My parents worked at GRN in the 90’s and 00’s, and I remember helping out on the assembly line for these occasionally. This was while the replacement mp3 player was being designed, and it was probably during that time that the last cassette players were produced. The cassette players were assembled by volunteer retirees, but the MP3 players were built offshore, I believe.

    From what I remember, the reason they didn’t use a spring or a clockwork mechanism was because they were designed for reliability in the field above all else. A little pack of replacement belts was stuffed inside each unit for when they wore out, and many of them were played for hours at a time every day for years and years with nothing more than those spare parts.

    If you want to see a real hack, check out the CardTalk – that was the original player that GRN made, and it was a cardboard record player. It was entirely human powered, and used the cardboard to hold the record and the needle and amplify the sound as well.

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