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Build A Nixie Tube Clock
J Aldridge writes: "People are still using Nixie tubes. Their warm glow seems to be the digital equivalent of the warm sound of vacuum amplifiers. One person has constructed a tube wristwatch."
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sounds dangerous!
When can I have one?
You can't legislate goodness. Let each to his own destiny, by will of his freely made choices.
My uncle was a classic tech scrounger, and had all manner of things that used tubes and early transistors. I fondly remember when he once showed me one of his prized posessions, a nixie tube calculator. It was maybe 25x25cm and the warm glow of the numbers was much friendlier than the simple black on grey of the LCDs I grew up with.
I could tell that even then it was something special by the way he treated it and obviously treasured it. It wasn't until I was older that I learned to appreciate the tech of yesteryear and the creativity and genius of those who created so much with the limited tools they had at the time.
These are breasts; this is source code.
Why do you have a problem with those two things belonging to one person?
Projects already on the back burner:
Dynakit STA-35 amp
Pioneer vacuum tube receiver (needs some small caps replaced)
Still enjoy my old Ampeg V7 tube amp, too. Digital circuits seem to take extreme proportions to replicate the functions of the simplest old analog circuits. Not alway for the better, either.
A feeling of having made the same mistake before: Deja Foobar
All TV sets and computer monitors are this way too.
If you work with the stuff it's a good idea to have an isolation transformer around (I've misplaced mine) There is a lot of High Voltage stuff in electronics. Know what you are dealing with, take all the right precautions, and hold one hand behind your back.
Take the cheese to sickbay, the doctor should see it as soon as possible - B'Elanna Torres, "Learning Curve"
Actually, all modern power supplies ARE isolated from the power line - that's the core of a switching power supply.
.1 amp, never work alone, one hand in your back pocket)) I design these things for a living.
First, the incoming AC is rectified to DC and filtered. This gives you 300VDC on about 10 to 1000 microfarads of capacitance - enough to kill you dead if it goes through your chest. That part of the circuit is directly connected to the power line.
Then the DC is chopped by a transistor and fed into a transformer (this is the "switching" part of the power supply). This chopping is done at between 60 kHz and 1 MHz (depending upon the power supply). The other side of the transformer (the secondary) is completely isolated from the power line. This voltage is then rectified, filtered, and supplied to the rest of the device. The voltage is measured, and fed back to the switching controller, which drives the switching transistor through either an optocoupler or pulse transformer, closing the feedback loop and regulating the voltage.
If you look at a modern switcher, you will usually see the "hot" side is completely isolated - even unto having sections of the PCB cut to prevent arc-over.
So, the bulk of the power supply, and the rest of the chassis, are NOT electrically connected to the power line. In fact, less of the system is connected to the power line than in an old style line frequency tranformer design. (Now, there were some old designs that rectified the power line and used that directly. THOSE designs were "hot" chassis designs, and were widowmakers...)
That said, you shouldn't go poking around inside a monitor or TV unless you know what you are doing. The anode voltage on the CRT is between 12kV and 25kV (although the source impedance is high enough that it won't kill you). However, the deflection circuits that sweep the electron beam across the CRT are at about 400V and have enough energy to knock you on your ass.
I've worked on TVs, monitors, radio transmitters (including tube based 250 watt repeaters (3kV at
www.eFax.com are spammers
Around 35 years ago, ur company used to build frequency counters using Nixie Tubes. One of our engineers got hold of some Nixie tubes that displayed dollar-signs. He built a device called "ExecuMeetingCounter". It had a couple digital thumbwheel switches labelled "attendees". You dialed in the number of people in the meeting and the device sat on the conference table and tallied up the cost of the meeting (using some arbitrary per-person cost).
Another fellow employee built a Nixie tube clock, but it used a 3-foot long glass PENDULUM as the rate determining device. A photodetector sensed the passing of the pendulum, incrementing the clock counters and sending a pulse to a coil to give the pendulum a "kick" to keep it going. It was an amusing mixture of old and new (at that time) technology.
The rule I was taught was to consciously decide not only to put one hand behind your back, but to hold your belt. I was also encouraged to think about holding my belt, to avoid the unconscious, "I just need another hand on the other side of this" which ends up with one hand holding a negative terminal and the other a positive, and the current running straight across your heart.
When I was 17 (before I'd been taught all that), I was helping a friend hook up an electric fence. The transformer had a wing nut on each side as a terminal, and was mounted to the wall by a nail at the top. For some IDIOTIC reason, I was trying to hook the fence up plugged in. Now, you often do have to work on live electrical equipment, but this was clearly not one of those cases.
So, in any event, I hooked up one lead, and was tightning the wing nut for one lead. Of course, since the transformer was hung from a single point, it was flopping around. Without even thinking about it (a lot of not thinking going on, that day), I swung up my left hand to stabalize the transformer... And grabbed the oposite terminal.
I remember standing there, with the muscles in my arms convulsing, and I thought, "I've got to do something." My chosen course of action was to yell "SHIIIIITTT!" at the top of my lungs. It didn't seem to improve my situation any, so I thought for a bit on what might be more productive. In one convulsive movement, I threw myself away from the transformer (my hands were locked to it by muscle spasms from the current).
So, children, that is why you should grab your belt with one hand, and hang on for dear life.