September 1945 Radio-Craft[Table of Contents]
People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Radio-Craft was published from 1929 through 1953. All copyrights are hereby acknowledged. See all articles from Radio-Craft.
Once mobile and other high-vibration and impact operational environments became the norm for communications, it became necessary to design hardware so that electronic components would not work themselves loose and cause intermittent or total failure. With vacuum tubes, placing locking shields over them did the job, but that caused other issues such as increased cost, poor cooling, and increased chassis size and weight. Some circuits with high power and/or frequency benefited from shields, but most did not need them. Sylvania introduced a scheme called "Lock-In" (trademark name of "Loktal")where the center pin incorporated a circumferential groove that latched into a capturing mechanism. It was strong enough to keep the tube properly seated but loose enough to be easily removed during servicing. Some models exploited the heavier metal contact for use as an electrical element. The downside was that although the pinout fit the standard octal base (8 pins), the contact diameters were smaller than standard pins (in order to facilitate higher frequency operation) so they made poor contact in standard octal sockets.
Wide use of "Lock-In" Tubes by the Military Seen Influencing Set Design
Repairmen Should Prepare For Servicing High Frequency Sets Carrying These Tubes
The armed forces have been using millions of Sylvania Lock-In Tubes of various types. During 1944 alone, millions of a single type tube, of lock-in construction, were supplied.
Why? Because the mechanical and electrical features of the Sylvania Lock-In are better, more rugged than any other tube made. Most important is the fact that, because of this electrical perfection, the lock-in can handle high and ultra-high frequencies much more efficiently, as necessary for FM and television.
Because of this special construction the Lock-In Tube has no trouble taking in its stride the recent FCC assignment of the band between 88 and 106 megacycles to frequency modulation. In fact it is right in step with the continuing trend of the industry toward higher frequencies.
Yes m'am, I carry those radio tubes especially made for this high frequency set.
Sylvania Serviceman Service
One of the most direct sources of information about the industry, particularly for radio servicemen, is Sylvania Electric's well-informed 8-page monthly bulletin - Sylvania News.
This interesting and helpful paper was started in the early 1930's for the purpose of supplying repairmen with a handy reference file that would contain past and current news of those items that would benefit them most.
Many features of special interest to radio servicemen are dealt with, making the 8-page Sylvania News a really helpful bulletin for repair shops all over the country.
Subscriptions are free to radio servicemen. To have your name placed on mailing list, just write to Frank Fax, Sylvania Electric, Emporium, Pa.
Lest We Forget
This Stands for Honorable Service to Or Country
Makers of Radio Tubes; Cathode Ray Tubes; Electronic Devices; Fluorescent Lamps, Fixtures, Wiring Devices; Electric Light Bulbs
Posted August 19, 2014