I was surfing the web looking for interesting projects the other day when I ran into [SkyKing’s] exquisite transistor demodulator radio builds. He mentioned that they were “Alfred P. Morgan-style” and that brought back a flood of memories about a man who introduced a whole generation to electronics and radio.
[Morgan] was born in 1889 and in the early part of the twentieth century, he was excited to build and fly an airplane. Apparently, there wasn’t a successful flight. However, he eventually succeeded and wrote his first book: “How to Build a 20-foot Bi-Plane Glider.” In 1910, he and a partner formed the Adams Morgan company to distribute radio construction kits. We probably wouldn’t remember [Morgan] for his airplanes, but we do recognize him for his work with radio.
By 1913, he published a book “The Boy Electrician” which covered the fundamentals of electricity and magnetism (at a time when these subjects were far more mysterious than they are today). [Morgan] predicted the hacker in the preface to the 1947 edition. After describing how a boy was frustrated that his model train automated to the point that he had nothing actually to do, [Morgan] observed:
The prime instinct of almost any boy at play is to make and to create. He will make things of such materials as he has at hand, and use the whole force of dream and fancy to create something out of nothing.
Of course, we know this applies to girls too, but [Morgan] wrote this in 1913, so you have to fill in the blanks. I think we can all identify with that sentiment, though.
Just when we thought we’d heard of all the cool early synthesizers, a tipster rattled our jar with news that someone completely restored a Novachord. These spinet piano-shaped prototypical synthesizers were made by Hammond for only four years. About a thousand of them were built before sales sagged and parts became scarce in 1942. It is estimated that only 200 or so are still around today.
The Novachord’s sounds are generated by a bank of twelve monostable vacuum tube oscillators. Each one is tuned to a pitch of the chromatic scale in what is called divide-down architecture. [Hammond] and his co-creators [John Hanert] and [C.N. Williams] used the property of dividing a frequency in half to generate the same tone, but one octave lower. This design means that all 72 notes can be played at the same time. Adjustable formant filters shape the often otherworldly sounds, which are then passed through flexible tube-based envelopes.
[Phil] knew it would be a big job to restore a Novachord in any condition. Thousands of passive components all had to be replaced. The cabinet bore all the hallmarks of a well-used parlor instrument—water rings from cocktails, scratches, and cigarette burns galore. [Phil] says that woodworking really isn’t his thing, but he did an outstanding job nonetheless of sanding every nook and cranny and applying several coats of stain. There are tons of drool-inducing pictures on his project site, and several clips of [Phil] really putting it through its paces.
About a decade ago I started a strange little journey in my free time that cut a path across electronics manufacturing from over the last century. One morning I decided to find out how the little glowing glass bottles we sometimes call electron tubes worked. Not knowing any better I simply picked up an old copy of the Thomas Register. For those of you generally under 40 that was our version of Google, and resembled a set of 10 yellow pages.
I started calling companies listed under “Electron Tube Manufacturers” until I got a voice on the other end. Most of the numbers would ring to the familiar “this number is no longer in service” message, but in one lucky case I found I was talking to a Mrs. Roni Elsbury, nee Ulmer of M.U. Inc. Her company is one of the only remaining firms still engaged in the production of traditional style vacuum tubes in the U.S. Ever since then I have enjoyed occasional journeys down to her facility to assist her in maintenance of the equipment, work on tooling, and help to solve little engineering challenges that keep this very artisanal process alive. It did not take too many of these trips to realize that this could be distilled down to some very basic tools and processes that could be reproduced in your average garage and that positive, all be it rudimentary results could be had with information widely available on the Internet.
If you ever wanted to build your own tube amplifier but you were intimidated by working with high voltages, [Marcel]’s low-voltage tube amp design might spark your interest. The design operates with a B+ (plate) voltage of only 40v, making it less intimidating and dangerous than many other amps that operate over 300V. It’s also incredibly easy to build—the whole design uses only 11 components.
The amplifier is designed around the ECL82 tube, which includes both a triode and a pentode in one package. The ECL82 is practically an amplifier in a tube: it was designed for low-cost electronics like record players that needed to be as simple as possible. The triode in the ECL82 is used as a pre-amplifier for the incoming signal. The pentode is controlled with the pre-amplified signal and acts as a power amplifier.
[Marcel]’s amplifier also uses a PY88 tube rectifier instead of semiconductor diodes, making it an entirely silicon-free design. Although [Marcel] hasn’t posted up detailed build instructions yet, his simple schematic should be all you need to get started. If you want some more background information about tube amps but you don’t know where to start, check out our post on basic tube amp design from earlier this year.
This lovely little number is the EF80 pentode thermionic valve, or vacuum tube, made by Mullard beginning in 1950. They were used in radio and radar applications, but most of them wound up in VHF television sets. This week’s Retrotechtacular takes a close look at the assembly of and on-site materials production for the EF80 in particular.
The film begins with slow and careful hand assembly of an EF80. The cathode is inserted into a mica disc, and a series of three grids are placed over the cathode. The semicircular anode sits around the outermost grid. Another mica disc is placed on top which does triple duty as a spacer, a base for the getter/plate assembly, and a firewall against the getter flash.The dark lining of the upper part of the tube is the residue of the vaporized getter, which is heated after the first stage of air removal.
The video was underwritten by Westinghouse, and as you can expect it has a bit of propaganda spin for the company. The time period in which the reel was produced is also telling. Coming about two years after the attack on Pearl Harbor, the applications for technology of the time are almost all military in focus. But we’re sure you’ll be entertained by both the film style and the tech explanation. It’s something of a How It’s Made of yesteryear. All twenty-one minutes of it are found embedded after the break.
[mkb] sent in a video he found of [Max Lamb] sandcasting a stool at a beach in England. The material is pewter, or >90% tin with a little bit copper and antimony thrown in for good measure. While we’re sure there will be a few complaints from environmentalists, it’s still a cool video to see.
Your project needs an OLED display
Here’s a Kickstarter for a tiny 96×16 OLED display. Connect this thing to any I2C bus and you get a 15×2 character display (or a graphic display if that’s your inclination) very easily. Thanks to [Chris] for sending this one in.
Here’s one for a larf
[Ryan Inman] is suing 20 companies because he got mercury poisoning from vacuum tubes. Read that last line again. Most of the companies that sell antique/repro/hard-to-find components like Angela Instruments, Antique Electronic Supply, and even eBay are listed as defendants in the case. This might put at least one company out of businesseven though they never sold [Ryan] a vacuum tube edit: they did sell him a neon bulb, and courts are generally idiotic when it comes to technological issues. It’s hilarious and sad, so we’ll keep you updated if we get more info.
Nostalgia, the pain from an old wound
The Adafruit blog posted an excellent piece on the Apple ][ game Rocky’s Boots, an educational game from 1982 that teaches kids how to connect logic gates. You can play this game in your browser, but we’d like to hear our stories of ancient video games that teach you engineering concepts like The Incredible Machine or Widget Workshop. Leave a note in the comments if we’re leaving any out.
A question posed to the community
A company is giving away credit card readers that plug into the headphone jack of an iDevice. [J Smith] writes in to ask us if anyone has gotten one of these and opened them up. Like [J Smith] we’re expecting something a repeat of the CueCat where free hardware is opened up to everybody. If you’ve done a teardown of one of these card readers, send it in.