LUFKIN, Texas - A friend and I got to talking about vacuum tubes the other day and quickly realized we were showing our age. At a minimum one has to be pushing the half-century mark to have hands-on experience with tubes - unless you're a nostalgia buff.

Long before computer chips, circuit boards and, before that, transistors, radios and televisions worked off tubes, which looked like small light bulbs except the bottoms had pins instead of threads. John Ambrose Fleming is considered the father of electronics because 100 years ago this fall he invented the vacuum tube diode, which was able to detect radio signals. His invention - and subsequent improvements made by others - ushered in the age of radio and, a few decades later, television.

Which brings me to the tube tester.

By the early to mid-1960s most radios were powered by transistors instead of tubes. Transistors had reduced the size of radios and made them portable. But televisions were still powered by tubes. In addition, many middle-class living room contained, as part of the furniture, a large tube-powered radio inside a wood-veneer case about the size of a dorm refrigerator.

I was a radio nerd as a child. When I was about 9 I built a crystal radio, from a mail-order set ordered from Heathkit. Crystal radios - the purest, earliest form of the medium - are like magic. They require no outside electrical source, because they're powered solely by the radio waves they attract. A quick perusal of the Internet indicates that kids both young and old are still building crystal radios. Later I built a "real" radio - complete with tubes along with a Heathkit volt-ohm meter as well, to test the circuitry I inexpertly soldered together. On occasion, a tube would malfunction somewhere inside the bowels of the radio I built or maybe in our cavernous black-and-white TV. It would be time for a trip to the corner store and the tube tester.

The tube tester was about the size of a slot machine. The top surface contained a number of sockets with different pin configurations. The upright portion had a gauge and needle, or maybe a set of lights ranging from red to green. My memory is a bit hazy.

Here's how it worked. You found the pin socket that fit the tube in your hand and pushed it in. The needle gauge or flashing lights would indicate if the tube was any good or not. If it wasn't, then you opened the doors underneath and searched through the bin of tubes stacked in small boxes on the shelves, until you found one whose number matched that of your tube. You handed the clerk a couple of bucks and headed home to plug in the new tube in high hopes the radio or television would spring back to life.

Vacuum-tube TVs died out quickly, once solid-state technology took hold in the mid-to-late 1960s. Accordingly, tube testers vanished nearly as fast as the Edsel. The only consumer item I can think of that vanished quicker than tube testers were slide rules, once pocket calculators became affordable in the early 1970s.

Now I'm really dating myself. You can still buy slide rules on e-Bay, but I haven't found anyone offering a tube tester for sale.

Gary Borders is publisher of The Lufkin Daily News, gborders@coxnews.com.

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