Radio Broadcast (Nov 1926-Apr 1927)

MARCH, 1927 ELECTRIFYING THE "HI-Q" RECEIVER 471 Det. P Fil. Switch 12l,mp. lllJacks 10 B + 180 9 B+ 90 8 B + 67JS 7.B+45 f To Filament \ windings of v Powe r Tr a n s. gfTo center tap Ion Fil. Trans. 5 C-, 1st. A. F. 4 C+ 3 B 2 A1 A + FIG. 2 terminals of the double resistor mounting at the end toward the main control panel. Connect the minus-F terminal of the second audio transformer to the terminal of the resistor mounting nearest the transformer and in the clips of the mount place the 50,000-ohm resistor. Mount a 1 .o-mfd. condenser on the baseboard directly opposite the double resistor mounting and connect one terminal to the soldering lug of the resistor mount which is connected to the F terminal of the transformer. Connect the remaining terminal of the resistor mount to the minus-C binding post (No. 6 in Fig. 2) and continue a branch wire to the unconnected terminal of the 1. o-mfd. condenser. A piece of double conductor lamp cord, about two feet long, should be connected to the filament terminals of socket No. 5 to be later attached to the power unit, as the filament of the 171 tube is to be heated by a. c. The output impedance should be mounted in the unoccupied space at the extreme left of the baseboard. The 4. o-mfd. condenser can be most conveniently mounted by making a small hole ■n shield section 2B and fastening the condenser against the side of the shield. Fasten the Imp telephone jacks in the small strip of bakelite and mount this assembly to the baseboard by means of the small brass angle bracket. In making the following connections for the output device, shown in Fig. 3, use No. 14 Celatsite or other well insulated wire: Make a connection from the P terminal of the power tube socket (passing the wire between shield sections iC and 2 A) to the P terminal of the output impedance. Run a wire from the 135-volt binding post to the B terminal of the impedance. Connect terminal Si of the impedance to one terminal of the 4.0-mfd. condenser, and the other terminal of the condenser to one of the Imp jacks. Connect the other Imp jack to the center tap of the filament transformer. THE POWER UNIT NOW let us tackle the job of building the power unit according to the diagram, Fig. 4, or the picture layout, Fig. 5. After the instruments are mounted in place, it only requires sixteen connections to complete the unit. The following is a list of the apparatus required: 1 Thordarson Power Compact, R-171 $15.00 1 Tobe B Block, No. 760 . . . . 11.00 1 Yaxley Automatic Relay, Type No. 444 500 1 Yaxley Cable No. 660 . . . . 3.50 1 Q. R. S. Red Top FullWave Rectifier Tube 6.00 1 Benjamin Socket, No. 9040 ... .75 2 Clarostats (Variable High-Resistance Units) ' . 4.50 1 Tobe Veritas Resistor, 10,000 Ohms. 1.10 1 Tobe Veritas Resistor, 5000 Ohms . 1.10 1 Sangamo Bypass Condenser, 1 .o-Mfd. Series B 1 .95 2 Lynch Single Resistance Mounts . .70 1 Baseboard, 7 x 9 x£ Inches ... .25 Total $50.85 4.0 mfd By pass Condenser, To filament windings of power transformer FIG. 3 For the sake of clarity in giving these instructions, we shall assume that the outfit is to be housed in a console cabinet as shown in the illustration, in which case the relay may be mounted on the inside of the cabinet. There is no set rule for laying out the instruments; the arrangement shown in the photograph on this page will be found to provide short leads and facilitate the wiring. Be absolutely sure that you leave sufficient room between the Thordarson Compact and the Clarostat to enable the cable plug being inserted in place without hindrance from either of these parts or the connecting wires. In wiring the powerunit, use No. 1 6 Celatsite, or No. 14 bus wire with Acme cambric insulating tubing. Do not use poor quality insulation. Three pieces of flexible rubber covered wire, about eighteen ortwenty inches long, are required, one of which is to be connected to the A-plus (red) terminal of the cable connector and another to the A-minus (green) terminal. Connect the remaining lead to the C terminal on the filament side of the power Compact. The A-plus wire is later to be connected to terminal No. 1 of the automatic relay and the A-minus is to be connected direct to the negative terminal of the storage battery. Terminal No. 2 of the relay connects to the positive terminal of the storage battery. The console makes an ideal installation as it permits the batteries, power-supply unit, charger, and other incidentals to be kept out of sight. It should be selected to harmonize with the other furnishings in the room where it is to be used. The Superior console, shown in the photograph on page 470, may be secured with a Stevens conoidal speaker built in the compartment at the top, or the loud speaker may be purchased separately to be hung on the wall or placed in a different part of the room. The compartment of the Superior console in which the "Fli-Q" is to be mounted, is in reality a drawer. It is unnecessary to remove the receiver from the baseboard on which the instruments are mounted. The console drawer is furnished with a walnut front slotted in the center to facilitate cutting out a section of the drawer so as to permit the panel of the " Hi-Q" to be mounted behind this walnut drawer front, as shown in the photograph. After this section has been cut out, a narrow walnut beading, such as is used in picture framing, should be fastened around the edges to give it a finished appearance. The "Hi-Q" should then be placed in the drawer and securely fastened in place. Fasten the automatic relay on the inside wall of the cabinet as shown in the illustration on page 472, and then place the storage battery and trickle charger in position. A number of convenient holes in the base-board have been provided for passing the cable and other connecting wires from the storage battery and power-unit to the receiver in the lower compartment. Pass the cable through the larger hole directly over the audio amplifier. Each lead of the cable (except the green and brown) has a little metal tag fastened to it indicating to which binding post of the receiver it should be attached. The brown lead should be connected to the B-plus 675-volt binding post and the green lead to the B-plus 90-volt binding post. Now connect the flexible wire from the C THE POWER-SUPPLY UNIT This device has been designed for use with the "Hi-Q" circuit, and supplies A and C voltages for the power tube in addition to B voltages for all the tubes in the receiver