Monthly Archives: August 2018

LED Chaser Tube

LED Chaser TubeI saw this really cool thing in a video about early computers that used vacuum tubes to make calculations. One type of tube had a ring of lights inside the end of it that chased each other in a sequential circle giving the impression of rotation.

I’ve always been charmed by the look of glass vacuum tubes from an early age when much of the electronics in things like radios and televisions used them. If you took the back cover off while the device was on you’d see a little forest of small glass bulbs, glowing white/amber. These were accompanied by resisters, capacitors and coils, all arranged on a brown board with lots of wires going all over. There was a smell of something hot and sort of melting. The warmth from the tubes was seeping out right at you.

Back in the 1980’s I found some large vacuum tubes (used in radio transmitters) at a flea market in San Jose California that I made into decorative lamps, by mounting the tubes above the big 6 amp transformers needed to light up the plate inside them and make them glow. They used a huge amount of power, and got very hot, but they sure looked beautiful. I experimented with a way to try and make them look beautiful like that, but not draw so much power. Using a small torch I melted a tiny spot on the side of the glass tube. The vacuum inside the tube caused the glass to melt inwards until it eventually burst inwards with a hole just big enough to wiggle a tiny “grain-of-wheat” light bulb into.  These are the little lights you often find in model railroads that only need 6 volts and very little current. If you held the tube so the wires were behind it, it looked just like a normally powered-up tube, but didn’t get hot at all. An electronics engineer friend in the Silicon Valley saw one of these on a sculpture I was making and commented on how cool the vacuum tube looked. He started looking all a round for the big 6 amp transformer that should have been there to give the tube its power. “Now wait a minute…There’s no…(still nosing all around) wait, you can’t just…” “All right (resignedly) how did you get that tube to light up?” I clued him into my little secret. “Looks convincing, doesn’t it?” “Yes, it does!” he said laughing.

The tubes I saw with the chaser lights in the video about early computers must have had small lights in them too, possibly neon. I decide to make a similar object by using a decade counter chip run by another chip that provides a clock signal. In place of lights, I assembled a rig of bright red LEDs. I had to cut the tube away from its base and cut out the original electronics to fit the LED assembly in their place. I’m really happy with the result! You can see a video clip of this thing in action at my KARF website: