Elegy for the color CRT

(This column appeared, in slightly edited form, in EE Times, January 22, 2007; it also contains a correction, marked with an *, to that print version)

No doubt about it: 2006 was the year of the flat-screen, as sales of LCD, plasma, and projection screens dominated the consumer market. The color cathode-ray tube (CRT) which has served us well for 50 years is now a dinosaur.

So be it. Our industry is one of innovation and progress, with little time for tears or remembrances. But it's worth understanding what the analog CRT represented.

In its color version, it was a part of a huge development effort across many disciplines. The Radio Corporation of America (RCA) invested over $1 billion of its own money in the 1950s (equivalent to over $10 billion today); to develop our NTSC-based color-television system. This was a solo corporate R&D effort, targeted at creating both a market and its product (the classic chicken-and-egg dilemma), somewhat similar but far more complicated than the Edison electric-light bulb and power-generation situation of the late 19th century.

RCA scientists, engineers, and manufacturing specialists worked many paths simultaneously, Reference 1. They developed a clever way to piggyback color information onto the existing monochrome signal, while ensuring both signal and receiver backward and forward compatibility; they used understanding of how the eye perceived color and images to evade technical limits; they came up with new ways to synchronize a local receiver to a signal's phase information via a color burst, they developed the image orthicon for capturing color images as well as its radically different complement, the mask-based CRT, for displaying them, to name just a few of the many battles they faced.

The CRT effort was especially difficult. It required research into bright RGB phosphors, and three synchronized guns squirting electrons at the shadow mask located right behind these phosphors. Making color CRTs broke ground in large-size vacuum-tube manufacturing, in making and precisely locating the shadow mask inside the tube, and in designing magnetic coils and matching drive circuits to deflect the electron beams, all for a high-volume, mass-market environment. Worse, if any piece of the signal path didn't happen, all the other pieces were useless; there was no “partial success”. You either won big, or had nothing.

It's easy to look back and say that the RCA engineers made short-sighted decisions, such as interlacing two fields to form a single image frame, or piggybacking the color information onto the existing monochrome encoding, but I disagree. It's easy to be smug with the hindsight of decades, and our advances in technology, and say “what they should have done is.” Reality is they did a brilliant job of working over, around, and through countless problems in an all-analog world, where the only digital system was the telegraph and a typical TV receiver had 200 vacuum tubes.

Of course, in our industry, being today's leader is no assurance of longevity. Ironically, last month the RCA accessories business* was sold for $50 million to Audiovox by Thomson SA, who acquired RCA from General Electric in 1988; Thomson still retains the RCA brand itself (click here). Paraphrasing Satchel Page, “don't look back, you might see someone (or something) catching up with you!”

1. “Tube: The Invention of Television”, by David E. Fisher and Marshall Jon Fisher, 1996.

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