A happy new year, 2007, the year of the (wild) boar.

Only 50 years ago, the dominance of vacuum tubes seemed to last forever. Those flimsy miniature tubes (mT) with dim filament glow controlled everything and everywhere. Radar, television, Hi-Fi audio, telecoms, even that young digital computer, too.

Gakken's Vacuum Tube Radio Ver.2 Some assembling needed, batteries included.

But along came that lowly Germanium transistor quietly. Followed by dirt-cheap silicon (no pun intended, because main ingredient of dirt is silicone) brothers. The rest is history.

Presently, only surviving vacuum tube is Braun tube (aka cathode ray tube/CRT) for PC display and cheap TV, though its death knell is about to toll. Your Mobile Ojisan grew up with vacuum tubes. His early training was done with clumsy eggplant-like standard tubes (ST), indestructible metal tubes, glass tubes (GT), miniatures, and funny acorn tubes, etc. So, whenever he sees a rare junk gear or two with blown-up tubes in Akiba junkyard, he just stops and reminisces about those good ole days for a moment.

Obviously, this kind of hopeless retro reactionary spirit survives strongly in Japan even after so many years of vacuum tube extinction. A publisher of educational and learning material, Gakken Co of Tokyo, publishes a popular scientific magazine for grownups, Otona no Kagaku (Science for Adults). This magazine had a special issue that gives subscribers a helping hand in assembling a vacuum tube radio, the real retro job.

Actually, the Otona no Kagaku sells the kit of this radio, "Vacuum Tube Radio Ver2", 9,800 yen (US$83). The kit is a three-tube job, regenerative detecton (1K2) and two successive stages of audio frequency (AF) amplifiers (1A2 and 2P3), the standard system of consumer radio in the 1920s and 1930s.

This project started when a huge stock of military surplus vacuum tubes was found and dug up in some undisclosed location in China. That ubiquitous inefficiency of state-owned firms of 30 years ago, or simple corruption... nobody could trace the reason for this mess-up anymore. Anyway, Gakken guys bought up these tens of thousands of 30-year-old vacuum tubes and built classic radio sets around the old but unused tubes.

Military surplus tube from China. "MILITARY" ( "Jun") stamp clearly visible on its surface.

To give some more retro flavor, tuning circuit was really overdone in the kit, its RF (radio frequency) coil being an antique loop antenna and its variable capacitor book type of 1920s throwback. And its speaker, another throwback of early Marconi days. A horn speaker!

Power source is not the Volta batteries, I'm afraid to say. Five regular 006P (9v) cube cells connected in series, producing +45V to drive three tubes. Another size C battery (1.5V) for lighting up three filaments, too. Works around 10 to 15 hours.

The kit does not need soldering job. A screwdriver (included) is enough. Simply wind the loop antenna and twist-connect several wires. That's all. You can tune into your local radio station, no problem. Sure, its sensitivity and audio quality are atrocious, but people of yesteryear have been totally satisfied with this kind of contraption. So you have to, too.

Only 10,000 kits have been offered. When the stock of tubes are gone, so will the history of vacuum tubes.

 

cheewee
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kaisei1
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