Radio Broadcast (May 1928-Apr 1929)

368 RADIO BROADCAST OCTOBER, 1928 FIG. 3. INSTRUMENTS AND WIRING ABOVE THE CHASSIS With the rotor plates of the condensers fully meshed, the position of the variable arm of resistor PP-2000, when viewed from the left end of the chassis in this diagram, should he two thirds of the way up towards the vertical on the left hand side. The coded holes in the chassis correspond to the numbers in Fig. 4. three New Jersey stations, wor. waat, and wkbo. In this location we are able to tune webh and wmbb in Chicago, kdka, and several other stations within a radius of 1000 miles. On several occasions, shortly after midnight, we have listened to programs broadcast by kfi and khj, Los Angeles, on a loud speaker. The Chicago stations were often mistaken for local broadcasters. All in all, the "Vivetone 29" is a receiver which is not difficult to build or operate, and which is sufficiently selective to cope with the present broadcasting situation and, with sufficient sensitivity to amplify weak signals up to the point where they can be enjoyed. LIST OF PARTS A S NOTED above, all the parts used in this receiver are of standard design, and may be replaced by equivalent parts of manufacturers other than those mentioned below. The type numbers of the parts listed below correspond with the lettering on the diagrams. 4 Hammarlund variable condensers, 0.00035 mfd., type ML-00035 1 Dubilier condenser, 1.0 mfd., No. 907 1 Dubilier moulded micadon condenser, 0.00025 mfd. 1 Hammarlund illuminated drum dial 1 Pair Yaxley phone tip jacks 1 Centralab potentiometer, 5000 ohms, type PP-5000 1 Centralab potentiometer, 2000 ohms, type PP2000 1 Centralab potentiometer, 15 ohms, type PP015 1 Centralab switch-type Radiohm, 200,000 ohms, type RS-200 3 Daven grid stabilizers, 400, 500 and 600 ohms. respectively 1 Dubilier Metaleak, with mount, 4 megohms 4 Aluminum Junior box shields 4 Benjamin Lekeless Transformers, No. 9072 1 Hammarlund coupling connector 1 Jewell voltmeter, 0-3 volts a.c, No. 190 1 Aluminum shielded chassis, "Vivetone 29" 1 Yaxley 12-wire cable connector and plug, No. 612 3 Benjamin 4-prong sockets, No. 9040 1 Benjamin 5-prong socket, No. 9036 i Micarta front panel, 7" x 26" 1 Corbett cabinet, 7" x 26" x 10" deep 1 roll solid Braidite wire 1 roll flexible Braidite wire 3 CX-326 tubes 1 CX-327 tube To make the set operative either of the Vivetone A-B-C-power-pack amplifier units, or the following accessories, are necessary: Audio amplifier of good design Filament transformer to supply if, 25 and 5 volts a.c. Source of B power (90 and 45 volts) C battery ( — 45 volts) FLEXIBLE. TWISTED BRAIDITE; TWO WIRES TOR EACH LEAD N8.I-RED \ N9.2-BLACK / CABLE COLOR CODE (V,V. N2.3 RED. WITH GREEN TRACER "1 2'/zV AC. N2.4 BLACK. WITH GREEN TRACER J A.C. NS.5RED. WITH YELLOW TRACER \ . v . r N«. 6BLACK WITH YELLOW TRACER J »»■ A.C. N9.TYELLOW. BN9.9 SLATE, B+90V N9 8 BLUE. B+4V. N9. 10 GREEN, INPUT. GND rr-n ANT. 422 BLACK 422 RED 21 TWISTED BRAIDITE; TWO WIRES FOR EACH LEAD. (HI THESE NUMBERS COINCIDE WITH THOSE ON TOP SIDE OF METAL BASE, AND MEAN THAT WIRES GO THROUGH HOLES IN METAL BASE. UNDER-SIDE VIEW OF METAL SUBBASE FIG. 4. THE UNDER SIDE OF THE CHASSIS The potentiometer, PP-015, is insulated from the chassis, and its shaft should not touch the aluminum. Care should also he taken in mounting the cable plug receptacle that its position is such that none of the pins will touch the aluminum chassis.