Welcome to the Old School: Restoring Antique Radios

Before the second world war Radio was a revolution in mass-communication much like the internet today. Fortunes were made and lost, empires built, epic patent battles ensued, all of which resulted in the world being more connected than ever before, which makes for a really great story (and a great Ken Burns documentary).

Last month we showed you how to modify a vintage radio to play your own audio source through it while re-using the existing electronics and maintaining its functionality. In this post we will show you how to restore any vacuum tube radio. You will learn basic repair/restoration procedures from a different era when it was actually worth repairing consumer electronics. Plug into history and get your hands on the most influential technology of the first-half of the 20th century!

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Keep those filaments lit, Design your own Vacuum Tube Audio Equipment

It was a cold January Saturday night in Chicago and we had big plans. Buddy Guy’s Legends bar was packed. We setup directly under one of the PA speakers less than 15′ from the stage. Time to celebrate. Skip the glass, one pitcher each and keep them coming. We’re about to make bootleg recording history. Conversation evolved into bloviation on what our cover art would look like, certainly it would be a photo of our battery powered tube mic pre-amp recently created in my basement lab. We had four hours to kill before Buddy’s appearance. Our rate of Goose Island and Guinness consumption would put us at three-sheets to the wind by 11. Must focus. It’s time, Buddy was on. Much fumbling about and forgetting how to turn on the Japanese-made 24 bit digital recorder with its nested LCD menus, cryptic buttons, and late 90’s firmware. Make it work. We did, just in time for the bouncers to notice the boom mike and battery packs. Wait, wait… maybe we should talk about why tube amps are worth this kind of trouble first.

Yes, vacuum tubes do sound better than transistors (before you hate in the comments check out this scholarly article on the topic). The difficulty is cost; tube gear is very expensive because it uses lots of copper, iron, often point-to-point wired by hand, and requires a heavy metal chassis to support all of these parts. But with this high cost comes good economic justification for building your own gear.

This is one of the last frontiers of do-it-yourself that is actually worth doing.

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Measuring The Lifespan Of Nixie Tubes

nixie

Nixie tubes have two things going for them: they’re awesome, and they’re out of production. If you’re building a clock – by far the most popular Nixie application, you’re probably wondering what the lifespan of these tubes are. Datasheets from the manufacturers sometimes claim a lifetime as low as 1000 hours, or a month and a half if you’re using a tube for a clock. Obviously some experimentation is in order to determine the true lifetime of these tubes.

Finding an empirical value for the lifetime of Nixies means setting up an experiment and waiting a very, very long time. Luckily, the folks over at SALTechips already have a year’s worth of data.

Their experimental setup consists of an IN-13 bargraph display driven with a constant current sink. The light given off by this Nixie goes to a precision photometer to log the visual output. Logging takes place once a week, and the experiment has been running for 57 weeks so far.

All the data from this experiment is available on the project page, along with a video stream of the time elapsed and current voltage. So far, there’s nothing to report yet, but we suppose that’s a good thing.

VFD Display Becomes an Amplifier

radio

Born well into the transistor era of the late 80s, [Fernando] missed out on all the fun you can have with high voltage and vacuum tubes. He wanted to experience this very cool tech, but since you won’t find a tube checker down at the five and dime anymore, where exactly do you get a vacuum tube to play around with? [Fernando]’s solution was to rip apart the vacuum fluorescent display from an old radio (Google Translate) and use that as a triode.

Inside every VFD is a filament, grid, and cathode – three simple elements also found in the triodes of just about every tube amp ever made. By applying a small voltage to the filament, a larger voltage to the cathode, and sending an audio signal to the grid, this triode amplifies the electrical signal coming from a stereo or guitar.

[Fernando] built his circuit on a breadboard, and with a little tweaking managed to get a fairly respectable amount of gain from parts salvaged from a radio. While using VFDs as amplifiers is nothing new – we’ve seen it a few times before, tube builds are always great to see, and bodged up electronics even more so.

Building a miniature x-ray tube

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We’ve seen homemade x-ray devices and we’ve seen people making vacuum tubes at home. We’ve never seen anyone make their own x-ray tube, though, and it’s doubtful we’ll ever see the skill and craftsmanship that went into this build again.

An x-ray tube is a simple device; a cathode emits electrons that strike a tungsten anode that emits x-rays. Most x-ray tubes, though, are relatively large with low-power mammography tubes being a few inches in diameter and about 6 inches long. In his amazing 45-minute-long video, [glasslinger] shows us how to make a miniature vacuum tube, a half-inch in diameter and only about four inches long.

For those of you who love glass lathes, tiny handheld spot welders and induction heaters, but don’t want your workshop bathed in x-rays, [glasslinger] has also built a  few other vacuum tubes, including a winking cat Nixie tube. This alternate cat’s eye tube was actually sealed with JB Weld, an interesting technique if you’d ever like to make a real home made tube amp.

AM tube radio restored and given MP3 playback too

mp3-antique-radio

This AM radio looks a bit like it did coming out of the factory. But there are a lot of changes under the hood and that faceplate is a completely new addition. The project really is a restoration with some augmentation and [Michael Ross] did a great job of documenting the project.

The Kenyon radio was built in 1946 and uses vacuum tubes for the amplifier. Considering its age this was in relatively good shape and the first thing that [Michael] set out to do was to get the electronics working again. It involved replacing the messy collection of capacitors inside. He then cleaned up the tubes, checking for any problems, and put the electronics back together to find they work great!

He cleaned up the chassis and gave it a new coat of finish. The original dial plate was missing so he built a wood frame to match a dial scale he ordered. The bell-shaped brass cover hides the light that illuminates the dial.

He could have stopped there but how much do people really listen to AM radio these days? To make sure he would actually use the thing he added an Arduino with an MP3 shield. It patches into the antenna port via a relay, injecting modern tunes into the old amplifier circuit. Catch a glimpse of the final project in the video after the break.

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