Also Be sure to see our
Audio tube listings ,
and
Octal radio tube listings ,
and
"G" Style Radio Vacuum Tube List
for more radio, audio and rectifier tubes.

Loktal tubes were designed for mobile radio use. The proper name is "Loktal" although the name is sometimes misspelled as "loctal" since "Loktal" doesn't look like the right spelling. The tubes "lock" into the socket via a spring clamp around the locator pin.

Often the tubes will have a black coating on the pins. This is not as bad as it seems. The pins are coated with silver to provide a better contact, but silver oxidizes with age which is the cause of the black color. Silver oxide is still conductive, although not as conductive as unoxidized silver.

Loktals had a short production life. Sylvania created them in 1938 as an alternative to the octal base tubes from RCA. By 1947 the tubes had fallen from favor. Probably the biggest cause of the failure was the difficulty of removing the tube from the socket because of the locking spring. This often resulted in scraped knuckles. Sometimes the tube base would remain behind still in the socket because the glue bond broke. Since the only locator indication on the tube is the base locator, that made it very difficult to figure out how to orient the tube to reglue it into the base. Generally it ment the tube was thrown out even if it was otherwise good.

The real death of the Loktals was probably driven by the rise of the 7 and 9 pin miniature tubes. They allowed manufacturers to make smaller radios, and since the miniature tubes didn't have a separate base, they were cheaper to make. Repairmen liked them because they were easier to replace and took up less storage space.

Like metal tubes, Loktal tubes were a good idea that didn't work out in real life.

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sales@mdbventures.com
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Due to the highly volatile nature of the tube business, all Prices are subject to change without notice.