General Electric Models G-105 and G-106
Radio Service Data Sheet
December 1938 Radio-Craft

December 1938 Radio-Craft

December 1938 Radio Craft Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Craft, published 1929 - 1953. All copyrights are hereby acknowledged.

General electric G-106 Vintage Radio (raddiomuseum.org) - RF CafeGeneral Electric engineers were really thinking 'outside of the box' when designing the 1938-vintage Model G-106 console radio. In addition to its stylish wooden cabinet, the 13-station, piano-keyboard-like 'Touch-Tuning' tuning scheme employed a motor-driven variable resonant tank circuit. No doubt the sound of a motor spinning inside was a major selling point for hooking techno-audiophiles of the era. There are some good photos of a restored GE Model G-106 console radio on the RadioMuseum.org website that includes details of the tuning mechanism.

General Electric Models G-105 and G-106

 - RF CafeGeneral Electric Model G-106·receiver featuring automatic program selection, Beam-a-Scope antenna, and touch-tuning. The pushbuttons are in the form of piano keys.

10-Tube Superhet.; 3-Bands (540-1,575 kc.; 1,575-5,700 kc.; 5,700-18,000 kc.); "Beam-a-Scope" built-in antenna; 13-Station Touch­Tuning System; Push-Pull Output; A.V.C.; Power Output (max.) 13 W.; Automatic (time clock) Program Selection (Model G-106 only)

Alignment Procedure. I.F. Alignment with Oscilloscope

Condenser gang at minimum capacity vertical input to ground and junction at R-25, R-12, and R-17. Adjust trimmers in order mentioned for a single . curve of maximum amplitude. . The resulting curve on the "Normal" position is shown in Fig. 2A. The expanded curve taken with tone control at "Treble 1" is shown in Fig. 2B.

Alignment Procedure. I.F. Alignment with Meter

Condenser gang at minimum capacity- output meter connected across voice coil volume control at maximum input as low as practical.

Mechanically adjust dial pointer to first line at left-hand end of dial scale with condenser gang fully meshed.

Connect output meter across voice coil - antenna switch turned to counter­clockwise position.

 - RF CafeAdjust; trimmers in order listed for maximum-output.

Adjust padder for maximum output in vicinity of 580 K.C. while rocking gang condenser.

Touch-Tuning

Figure 1 shows a simplified schematic of the control circuit and the following cycle of operation may be traced very easily. When a key is depressed. it completes the 23-volt circuit through the button making contact with the contact segment (CT) and energizes one winding of the motor. The other winding on the motor is energized through the condenser C51. The direction of rotation of the motor is dependent upon whichever half of the contact segment (CT) that the station button first energizes. When voltage is applied to the motor, the rotor is pulled further into motor field. and engages its rubber cone hub with the dial drive wheel which in turn rotates the gang condenser and contact segment (CT). This operation continues until the insulated segment (1) breaks the station button circuit to the contact segment and removes voltage from the motor. The inertia in the tuning system drives the insulated segment past the station button and makes contact with the other half of the contact segment. This ener­gizes the other winding of the motor and causes the motor to reverse. The brake on the dial drive wheel· does not allow the tuning

 

 

Posted May 17, 2017

Radio Service Data Sheets

These schematics, tuning instructions, and other data are reproduced from my collection of vintage radio and electronics magazines. As back in the era, similar schematic and service info was available for purchase from sources such as SAMS Photofacts, but these printings were a no-cost bonus for readers. There are 220 Radio Service Data Sheets as of February 2, 2018.