3517 RALEIGH AVENUE, ST. LOUIS PARK, MN 55416
The 2016 Radio Workshop
One of the many highlights of this year’s annual Radio Workshop, sponsored by the Northland Antique Radio Club, was Gary Ball’s presentation on Zenith’s first transistor radio, the Royal 500 (shown above). Their unique placement of the volume and tuning knobs gave them the nickname “Owl.” When they were introduced in November 1955, sales took off and exceeded all expectations. It was an expensive item for the day at $75 (equal to $663 in 2016 dollars). During its 10 year run, the 500 would undergo six design changes and experience many chassis revisions.
Zenith sold about 100,000 of the hand-wired units. To keep up with the high demand, they had to use three different transistor suppliers. The majority were made by Sylvania in the 7XT40 chassis. Texas Instruments supplied them for the 7XT40Z1 chassis, while Raytheon parts went into the 7XT40Z chassis. Raytheon transistors cost Zenith 25% more to purchase so they were the last option. As a result, hand-wired Royal 500s with a Raytheon chassis are a rare find but easy to recognize because of their bright purple color. All three versions used (7) transistors, (4) AA batteries, and produced 0.1 watt of undistorted power.
Gary was kind enough to end his presentation by giving away free DVDs of the 2011 edition of his Zenith Transistor Radio Photo and Price Guide. To learn more about Gary’s new edition of the Price Guide, go to Garysradios.com.
Glen Berg’s presentation last year on repairing crystal phono cartridges was going to be hard to top, but he put together another fine demonstration this year showing us how to make new paper cones, from scratch, for 1920s era loudspeakers. It was wonderfully creative and complete with a variety of beautiful examples.
We asked people to bring their favorite phonograph or turntable this year.
The CardTalk is the world’s simplest phonograph. It was used by Christian missionaries to play religious talks in remote parts of the world that did not have electricity. It consists of a flat piece of cardboard creased and folded into a triangle. The base has a nub to hold the record in place. The upper "arm" has a needle which is placed on the record. The record is spun using a small pointed object like a pencil. The cardboard vibrates loud enough to be heard causing the "Card" to "Talk." Several cardboard phonograph devices were patented around the same period, including the Jauquet (1953) for a "Pocket Speaking Device", J.S. Wiener's "Sound Emitting Device" (1967) and the "Record Player" of Max Meier-Maletz (1972). Ours came from the Jack Mullin Collection.
Here’s a 1949 “Player Attachment” branded “Columbia” but actually built by Philco. Columbia introduced the Long Playing "microgroove" record format in 1948.
We also showed off this great little RCA 6BY4A single-play, portable radio/phono combination. It uses a conventional battery pack to power the tubes and (4) “D” cells to run the motor.
Kip Wallace brought in this blue Thorens Excelda portable gramophone. From the outside it looks like an old Polaroid Land Camera. The first models made in 1935 were available only in black with an internal wooden horn and a mica diaphragm. In 1942 they became available in “crackled” black, red, green, gray, blue, and brown with an internal metal horn. Production of Exceldas ceased around 1947.
Jim Thompson brought in a couple of interesting examples, including this 1983 Sony PS-F5 Flamingo portable linear tracking turntable and a 1984 Panasonic SG-J500 boombox with a built-in turnable.
Matt Hyman brought in an 1899 Columbia “Q” and a modern, outside horn gramophone kit made by Gakken capable of playing 33, 45, and 78 rpm records.
Aimee Sahlsteen brought in a Columbia stereo that originally sold for $7.95 in 1962.
John Findley shared this streamlined 1940 Arvin model 302.
But the real show-stoppers were Jeff Hed’s Peter Pan portable gramophone and his Swiss-made, 1926 Mikiphone “Portable Pocket Phonograph,” complete with an original needle tin. The Mikiphone folds down into a round can small enough to fit in your back pocket, while the Peter Pan folds down to the size of a small box camera.
Allen Lein always has a new design or two to keep things exciting. This year he brought in an output transformer impedance tester and a loudspeaker impedance tester. These can be real time-savers when you’re stuck with a missing speaker or output transformer. Both designs incorporate a built-in 400Hz sine-wave oscillator. From Howard Tremaine’s Audio Cyclopedia, “As a rule, the impedance characteristics of a loudspeaker are measured in the enclosure used with the system.” Tremaine also recommends using a “400 cps signal” to test full range speakers. Here’s the circuit for Al’s audio oscillator. To see complete circuits and construction details for all of Al’s designs go to pavekmuseum.org/Lein.html
It wouldn’t be a Radio Workshop without a presentation by Ken Ladd. This year Ken brought in a thermopile heated by a homemade alcohol burner. He was able to produce 800 millivolts which he hopes will operate a low-voltage radio that he is designing. Ken also showed us a nifty device called the “Rock-it.” It’s a small amplifier coupled to an adhesive backed transducer capable of turning anything that will vibrate into a loudspeaker. Go to origaudio.com to learn more about the device. Ken also showed us a picture frame that he made from an old television mask.
Thanks to everyone who put together a presentation, brought in a phonograph (or two), and helped set up food and drinks for everyone.