标签: vacuum

All I can express is that I am flabbergasted. In fact, I would go so far to say that it's rare indeed for my flabber to be quite so gasted. I was sitting here in my office slaving away over a hot keyboard when my chum Charles Fulks unexpectedly breezed in.   Charles (he lets me call him that) leads the FPGA development group for Intuitive Research and Technology just down the road from me. I shared the stage with Charles and RC Cofer at this year's EE Live! Conference and Exhibition.   You can only imagine my surprise to discover that Charles had brought me a little something. There's an old saying that goes something like "Beware of Geeks bearing gifts," but I certainly wasn't going to look this gift horse in the mouth, because this little beauty was a vacuum tube radio from the early 1940s.   Amazingly enough, I have the perfect spot for it. The photo below shows the bay outside my office. The comfy chair and ottoman in the foreground allow one to take a few minutes' break now and then. Standing against the wall is a 100-plus-year-old wooden chest, upon which rests the frame for my ongoing mosaic project -- and now my beautiful vacuum tube radio.     In case you were wondering, this bay is where I seem to end up storing the furniture my wife doesn't want me to keep in the house (LOL). On the left side of the above picture, you can see my office door. (Mine is the one with the dragon on the far wall.)   The radio is a Grundig 5088. (I need to see if I can find the circuit diagrams somewhere.) This is an AM radio with multiple ferrite rods for long-wave, medium-wave, and short-wave reception.     Charles says that, when he acquired this little rascal several years ago, he was told that it did work, though he's never tried it himself. As soon as I get a free moment, I'm going to power it up, but I will have a fire extinguisher standing by, just in case.   I would love to have this radio playing in the background in our bay. Something about the sound that comes out of a vacuum tube radio makes you want to use words like "smooth," "sensuous," "robust," and "rotund."   Of course, chances are that this little scamp won't fire up the first time. It wouldn't surprise me if we needed to replace the paper capacitors and suchlike. The problem will come with the vacuum tubes. I'm reasonably sure I will be able to pick up anything I need at the Huntsville Hamfest in August (subject of a blog post last year). The real trick is to determine which tubes need replacing.   But where can one find someone who knows how to diagnose and debug problems with vacuum tube-based systems these days? Well, you could have knocked me down with a fishwife (much more effective than feathers) when I discovered that my chum Ivan in the next bay is a diva with vacuum tubes.   Actually, this really shouldn't surprise me by now. Ivan is one of the cleverest guys I know. (Yes, I'm buttering him up; I want him to fix my radio.) When I called Ivan over to see my new acquisition, he foolishly informed me that he used to repair radios and suchlike. Upon further questioning, I discovered that Ivan that was in an accredited trade school while in high school (he crammed standard classes and electronics classes in alternating weeks), and that this involved repairing electronic systems. While in the Air Force, he focused on maintaining and repairing electronic systems. After leaving the Air Force, to supplement his income at college, he worked at Magnavox repairing everything that came his way: CB radios, record players, AM/FM radios, TVs, laser disk players, alarm systems, audio amplifiers, PA systems, walkie-talkies -- the list goes on. Do you ever get the impression that some things were just meant to be? I have a vacuum tube radio that needs some love, but I don't have the skill to treat it with the respect it deserves. Ivan has skill oozing out of his fingertips, but no vacuum tube radio to unleash it on. It's like a marriage made in heaven (LOL).

Have a sit and be ready to be flabbergasted. I have news so exciting that I can barely bring myself to speak of it. In my earlier blog on my Ultra-Macho Prognostication Engine project , I mentioned the idea of mounting vacuum tubes on top of the engine and then lighting them from underneath with tri-coloured LEDs. The following mock-up gives a rough idea as to what I was thinking:   Now, I have a huge bag of non-functional small vacuum tubes I could use, but we really need something more grandiose for this project. Originally, I had toyed with the idea of using the 12-inch-tall antique vacuum tube I have in The Pleasure Dome (my office) as shown below:   When push came to shove, however, I simply could not bring myself to take this little beauty out of its transportation frame. Thus it was that a few days ago, on the way into work, I popped into Mock Electronics (a store so amazing that describing it as "An Eclectic Emporium of Electronic Elements" fails to do it justice). My hope was to find a really large tube to act as the centerpiece of the display, and indeed I found an absolute beauty—a monster in size, with an outgrowth of glass on one side, jam-packed with strange and wondrous internal structures. The only problem occurred when I turned this beauty over and discovered its $275 price tag. Once I'd regained consciousness, and various nervous twitches and tremors were under control, I moved on to see if there was anything I could actually afford. You can only imagine my surprise and delight to discover a box of rather interesting 500W bulbs (only a few dollars apiece), one of which is shown below:   I should have placed a ruler next to this bulb when I took this image, but I forgot, so you'll just have to take my word that it's approximately 4.5" in diameter. When I arrived at my office, I took this bulb to show to my chum Ivan, and we whipped it onto the test bench and powered it up. At about 21V, the filament gives a very satisfying red glow. That's not what we're seeing here, however, because the filament isn't being powered in the above image. Observe the faint rainbow-coloured lights at the bottom of the bulb—just where the base of the bulb goes into a hole I cut in the top of a cardboard box, which is acting as a poor man's prototyping platform. For this first test, I connected four of Adafruit's Flora NeoPixels. (These were kindly sent to me some time ago by EE Times Chief Community Editor Caleb Kraft.) Unfortunately, the above photo doesn't do this justice. It looks a lot better in real life. Here's a slightly better image with the room's main lights turned off:   Once again, even this image doesn't really convey what this looks like to the human eye, which is a sort-of aurora borealis-type effect as shown below:   Having said all of this, even though the effect I've achieved thus far is rather tasty, it really doesn't stand out enough in bright light. This led me to conceive a cunning plan. Have you seen that glass-etching cream you can get from places like Hobby Lobby, Michaels, and Wal-Mart? The idea is that you first apply some sort of stencil to your glass (painter's masking tape will do), and then use this cream to etch the glass leaving a frosted effect as shown below:   This explains why I was to be found roaming around Michaels yesterday purchasing a jar of this cream. My idea is to frost the top and bottom of my bulb, leaving a wide stripe around the middle unfrosted so that we can still see the glowing filament. I think that this frosting will act as a display screen that captures the light from the LEDs and makes the overall effect much more interesting. In turn, this explains why this morning on the way into work I once again headed down to Mock Electronics to purchase some more of these bulbs to play with, and I did indeed pick up three more (better safe than sorry) as shown below:   I'm still planning on performing my glass-etching experiments this evening, just to see what will happen. I'm sure these bulbs will find a home in future projects. Unfortunately, I have to say that I no longer plan to use them as part of my Ultra-Macho Prognostication Engine. Why? Well, as soon as I walked through the front door, the folks at Mock Electronics said "Guess what we've discovered hidden away in the depths of the store?" And then they whipped out a box of the most amazing old vacuum tubes as shown below:   OMG! Can you imagine what these will look like on top of the Ultra-Macho Prognostication Engine when they are illuminated from inside with tri-coloured LEDs. There is a slight problem (isn't there always?). I don't want to do anything that could potentially damage these tubes—not that they are actually capable of performing their original function, you understand, but I don't want to crack the glass. Fortunately, I do have a cunning plan... which we will discuss in a future column. In the meantime, what do you think about these new tubes? You have to agree that they are going to look absolutely amazing on top of the Prognostication Engine.  

As written in Ogilvy On Advertising, David Ogilvy says there are three magic words in the ad world. Put one in the headline of your ad and people will read it. The magic words are new, free, and sex. But the one sure way to get my attention when flipping through a magazine is to have a schematic diagram. Any kind. A radio. Vacuum tube circuits. Logic. Piles of op amps. For some reason I find schematics arresting and always stop and take a closer look. Clicking around the web recently I stumbled across some vacuum tube sites, which brought back fond high school memories of building tube ham radio transmitters. Everyone relied on the RCA Vacuum Tube Handbook as the bible for specs on the parts. Wouldn't it be cool to find an old copy? And wouldn't that be utterly pointless? That thought morphed to memories of the other indispensable tome of the time: The GE Transistor Manual. Not too many clicks later and one was on its way here. I ordered the 1964 version ( below ). What's astonishing is how much was known about transistor theory by that date; transistors had been in common use for just a handful of years at the time. And this is the seventh edition!   Yet it explains transistor theory in a level of detail that my college classes almost a decade later never approached. Read – and understand – the first 170 pages and you'll be a transistor expert. But no attempt is made to make the subject easy. The price on the cover is $2, though it cost me, used, $6.98. Alas, the one that arrived is the "light-weight edition," a 594 page subset of the full-blown one I remembered. The light-weight version is missing all of the detailed specs of the transistors GE once made. The GE Transistor Manual was, and still is even though it has been out of print for generations, one of the best compendiums of information about designing transistor-based circuits. Part of its appeal was that it's just stuffed with schematics of every conceivable kind of circuit ( figure ).   One can get lost for hours and days studying the cool ways the authors crafted designs with an astonishing economy of parts. It's engineer porn, graphic illustrations that makes one's heart beat a little faster as one furtively flips from page to page, mostly not reading the "story" but gazing deeply at the pictures. Old timers will remember the unijunction transistor. There's an entire chapter dedicated to its use. These were used in timer circuits in the pre-555 days. UJTs are still available, though it has been a very long time since I've seen one in use. But there's no discussion at all about FETs, which today represent, to a first approximation, 100% of all of the quadzillion or so transistors made every year. Though FETs existed at the time, they enjoyed little commercial success, and even into the 70s were seen as niche products. Its exclusion from this book suggests that GE did not make any at the time. Some of the components discussed are obsolete. Or, at least I thought they were till checking the web. Stabistors, for instance were low-voltage zener diodes, but it seems these are still available, and one can even get them in modern SOT packages. Are SNAP diodes still around? There's a good description of them in the book. Those who enjoy tech nostalgia – or schematics – will get a kick out of the book. If you want a deep look into transistor theory and use, this is a great resource. Copies can be found on Amazon.