SIGNALS

I love tubes. You love tubes. Everybody loves vacuum tubes. Of course, the ultimate vacuum tube is a cathode-ray tube — the glowing heart of good, old analog televisions. What a cool invention — a device that can input electrical signals and convert them into visible moving images. Hmm — would it be possible to build your own CRT as a DIY project? You betcha!

In these pages, we have recently returned to those thrilling vacuum-tube days of yesteryear. We discovered that the technological simplicity of vacuum tubes means that a modestly skilled amateur can make DIY vacuum tubes, and not only that — can use them to make a functioning audio amplifier. But what about televisions? Literally the most visible part of an analog television is a vacuum tube. That is, its picture tube. And, like audio amplifier tubes, you can build your own CRT using modest tools and skills.

Among several similar videos, I particularly like this video. The YouTuber does a terrific job of explaining the from-scratch build. And “from-scratch” I mean fabricating the internal elements, blowing the glass tube, applying the phosphor, etc. At the 25:30 mark, the builder tackles the tricky problem of procuring phosphor. His solution, employing creative destruction, violates every safety warning known to government and man, and also is immensely ingenious.

In the end (at 1:07:20) the builder's CRT does indeed work as advertised, displaying the applied waveforms. The builder admits that the result is “primitive” and yes, the picture quality is essentially non-existent. But that's not the point. Rather, the project helps us to appreciate the essential elegance of this once-revolutionary technology. Actually, this DIY CRT probably looks a lot like the very first CRT prototypes, devised in the late nineteenth century. And, while we fully understand and expect the result, whereas the original inventors stood before the great unknown, our untidy glass tubes and tangle of wires lets us relive some of the wonder of their discovery.

Well, I hope you have enjoyed these DIY audio/video vacuum tube projects. Never underestimate the power of a slightly crazed person in a basement workshop. Next time: How to build your own lunar lander. Just kidding! Or am I?

Postscript #1 For your viewing pleasure, here is another YouTube video showing the troubleshooting and repair of a vintage (1949) television. This Motorola VT73 set (with a jumbo 7-inch screen!) is a real beauty, wired point-to-point in the days before printed circuit boards. They don't make 'em like that used to. And sometimes that's a good thing.

Postscript #2 A note from the esteemed Sound and Vision legal department: If these videos inspire you to build your own CRT or otherwise poke around them, please take all necessary safety precautions; there are a beaucoup number of power supplies here, including a high-voltage supply with all of its attendant dangers. Toying with televisions in your basement is not for the faint of heart, or the slipshod.

Postscript #3 Whatever happened to your old television? You know — that sweet cathode-ray TV? It's been a while. Oh, I remember now. From its privileged place in your living room, you moved it to your bedroom, then to the guest room, then to the garage. Then you put it out on the curb. But it just sat there. No one wanted it. Finally, you took it to a recycling place and tossed it on the analog pile. Then you drove away. You never even looked back. Sad face.