Radio Digest (July 1924-Apr 1925)

18 RADIO DTGES T— Illustrated April 4, 1925 FOUR FILTER SUPER (Continued from pnge 15) terminal In the lower row on the (liter box, which has been designated PI. connections shown In figure 15 leading to the Biter bos all connect to the terminals in the lower row. The connections for the terminals in the upper row are shown in figure 17. Tn figure 16 it Will be noted that there are no wires leading down through holes 29, .'!0 and 31. References to figure 17 will show the wires that pass down through those holes. Figure 10 BhOWS where these three wires connects to the grid of the oscillator tube as shown ill figure 1">, and its connection is continued around the circular part of tin socket and up to the stator plates of I be oscillator condenser C2. The lower end of the plate coil connects by a short wire directly to the P terminal of the oscillator tube socket. Part of the connections at the left end of the panel and sub base have had to bi omitted for clearness, as otherwise there would be too many wires and it would lie impossible to follow them. Reference to figure 2 should make this wiring (bar and it will be seen that the two Ore O x-i i <w O TO CENTER. O TC-1 POTENTIOMETER TC-4 °p-, °c-i jB+2 F-E jB+3 F-3 lB+4 F 4 O x-2 0 o P-E G-2 o o x-3 x-<v O O 0 o P-3 G-3 P-4 G-4 'i .9 30 31 Pigure 17 lead below the sub base. The wire from hole 2'.< runs to the plus 45 binding post, which is the second from the left, and is continued across to the right and then forward to one of the long springs on the double circuit jack which is in the plate circuit of the second detector tube, ft will lie noted in figure 16 that a wire is tapped off which passes up through hole 28 to the oscillator coil. Oscillator Coils The plate coil is the center of the three toils wound on and this wire leading up through hole 28 connects to the upper end of this plate coil. Figure 2 shows the rotor plates of the oscillator condenser connected to one end of the grid coil and also to the negative filament bad. In figure 15 the rotor plates are con■d to the negative filament where it comes up through hole 20 to the negative terminal on the oscillator tube socket. The prid coil is the topmost of the three coils wound on and its lower end is dropped through hole 22 to connect to the negative filament connection as shown in figure 16. The upper end of the grid coil London, Madrid Newcastle, Aberdeen— that's just a few of them AGAIN Elgin Super-Rein•*■ *-artz leads all others! Every trans-Atlantic report investigated was found to be ABSOLUTELY authentic ! Many happy owners of Elgin sets again tuned in the European stations. ELGIN The Ford of Radio " will give you the selectivity and distance it has given others. And you can save $50.00. Let us tell you how — FREE Mail the eouoon TODAY (or the complete working drawings ot the famous Elgin SuperReinarf. the set that gets the distant stations. They are free — no obligations, just a stamp tor postage, please! tear out this coupon— .... 5 RSSte*1* ■ ■ ■ ■ ■ >RINT In pencil! ends of the secondary of the antenna coupler connect to the two short springs of the double circuit jack, while the center tap on the secondary of the antenna coupler connects to the single short spring on the closed circuit jack. The rotor plates of the midget condenser of .000045 mfd. capacity, in addition to connecting with the rotor plates of, the loop condenser, as indicated in figure 15, also connect with the long spring of the two circuit jack, for which no connection is indicated in figure 16. The wire from the plate of the second detector tube which passes down through hole 27, and is the only wire remaining which carries any Radio frequency current, connects to the remaining long spring of the double circuit jack to the right. Audio Frequency With all the Radio frequency leads now in, and presumably placed up close against the under side of the sub base, the audio frequency leads can be put in and so bent that they will be about % inch below the sub base, where they are underneath. The input terminals of the first push pull The "Goode" Two-o-One A Le Ton d'artjent Postpaid QUARTER AMPERE AMPLIFIER — DBTBCTOK RADIO TUBE GUARANTEED SATISFACTORY All "GOODE" Tubes Sold Direct to the Consumer — No Dealer Profits $1.89 5.00 ONE — "Goode" Detector-Amplifier THREE— "Goode" DetectorAmplifiers (All postage prepaid) The "Goode" Two-o-One A Tube ampules or detect!. It l» a quarter ampere. Ire rolti, itandard bate silvered tube. Send express or postal money order — New York draft — or personal check to — The Goode Tube Corporation Incorporated Owensboro (Dept. A) Kentucky transformer are run down through holes 13 and 14 and connect to the two short springs of the double circuit jack. One of these input terminals is marked P, so he sure that it connects to the short spring which makes contact with the long spring connected to the plate of the second detector tube when no plug is inserted. Next connect the two outer terminals on the output side of this first transformer to the grids of the amplifier tubes as shown in the upper right hand corner of figure 15. The center terminal on this output side connects to negative on the C battery, while the plus side of the C battery is connected to the negative filament circuit at the point where a wire comes up through hole 15. The two outer terminals on the input side of the second transformer are to be connected to the plates, while the center terminal drops through hole 17 and, as shown in figure 16, connects to the plus 90 binding post beneath the sub base. It will be noted in figure 16 that this wire from the plus 90 binding post also goes up through hole 30 and, as shown in figure 17, connects to B plus 2, B plus 3 and B plus 4. To complete the audio frequency circuit, wires are dropped from the output, side of the second transformer through holes 18 and 19, which, as is shown in figure 1 6, go to the spring and frame of the open circuit jack at the right hand end of the panel. The grid return on the second detector tube is shown in figure 17 as a wire from F4 which is to drop through hole 31 and, as shown in figure 16, connect to the plus filament bus beside hole 12. The oscillator coil shown in figure 15 is the type wound on a solid tube. If the low loss coil was made, two U-shaped pieces of heavy brass are connected to the ends of the bakelite or hard rubber strip, one at the top and one at the bottom and also to the front panel, so that this coil will be supported in the same position as that shown for the solid tube coil. Since the average rheostat is not more than 1% inch deep this coil will clear the rheostat by at least % inch. Grounding Filter Box As can be seen in figure 15, the filter box is held in position by two small right angles, one at the rear left hand corner and one at the front right hand corner. The machine screw which holds this right angle at the front right hand corner passes through the sub base and is secured on the underside by a hexagonal nut. The filter box is grounded by connecting this machine screw to the nega /////////A/A-,../,-7777n-S>t<-. WV//JMWM/&A \ '////.■aw/. w I I i vmmmm^ /<?'«* <^» \M> 1 If ¥i. ■////. 'M p w> ''///.< $& m % m u p mi M il i V/. m f It m m 1 ■J-: W/A w. i : Distance on the phones — with certainty and regularity — on the Crosley one-tube SO. The radio which told the world that the MacMillan North Pole expedition was safe and sound. The radio that kept communication open to Leonard Weeks at Minot, N. D., when all other receivers failed. There is nothing better than the Crosley 50 for the radio beginner. There is nothing to excel M in value; unless it be the larger Crosley sets. Stations always come in at the same place. For sale by good dealers everywhere. Other models priced from the two tube 51, at $18.50, to the Trirdyn Special with sloping panel, at ?C5. All Crosley Radios are licensed under Armstrong Regenerative U. S. Patent 1,113,149. Prices quoted are without accessories. Prices West of Rockies — Add 10% Write for Complete Catalog The Crosley Radio Corporation Powel Crosley, Jr., President 4491 Sassafras St. Cincinnati, Ohio Crosley owns and operates Broadcasting Station WLW ^^^^^^^y^^^ tive filament bus which passes it about Vs inch to the right. In addition to being bolted to the filter box, this right angle should also be soldered to it to make a good electrical connection. The connection between the grid returns of the intermediate transformers and the center binding post of the potentiometer is not shown in figure 15. Figure 17 shows Fl, F2 and F3 connected together and this wire is to be bent forward so that it passes just to the left of the third intermediate tube socket which will bring it right in line with the center terminal of the potentiometer to which it is connected. Fixed condensers, with the exception of grid condensers, have not been shown in any of these diagrams as they would, in place, obstruct the view of the wiring and make it too complicated to follow. Condensers C10 and Cll are two of the .5 mfd. bypass condensers and they may be secured either to the back of the front panel on each side of the potentiometer or may be fastened to the upper or lower side of the sub base close to the potentiometer. The third .5 mfd. bypass condenser is condenser C9 in figure 2. C14 is the .006 mfd. fixed mica condenser, while C8 is the .002 mfd. fixed mica condenser. C14 and C8 can be attached to the wiring on the underside of the baseboard toward the right end of the panel and supported by their connections to the wiring. The more experienced experimenter will doubtless now be able to adjust and operate the receiver by himself but for those not so familiar with this work the details on adjusting the filters, with instructions for tuning, will be presented next week. A picture layout for the connections, when two stages of audio are used instead of push pull, will also be shown. For those who have not as yet laid out the sub base it should be stated that in figure 11 the distance from the right edge of the sub base to the center of the output audio transformer should be 3% inches instead of 4 % inches as shown in upper right corner. (The wiring as explained above is identical in every respect with, that in Mr. Fournier's own set. The method by which he adjusted the intermediate amplifiers when demonstrating this set to the editors will be presented just as clearly in the next article. — Editor's note.) Super-Het Builders! MURDOCK. 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