Radio today (Sept 1935-Dec 1936)

JVEW Power Output TUBE TESTER TESTS ALL TYPES METAL AND GLASS Model No. 1501 Dealers Net Price $46.67 NEW TRIPLETT MULTI-PURPOSE TUBE TESTER No. 1501 combines ten instruments in one. Here are the ten instruments: 1. Test all type tubes (New Power Output Test) 2. Neon Short Test 3. Separate Diode Tests 4. Neon Paper Condenser Tests 5. Electrolytic Condenser Leakage 6. D.C. Voltmeter and Milltammeter 7. Ohmmeter 8. A. C. Voltmeter 9. Decibel Meter 10. Impedance Meter Radio dealers have always wanted a tube tester that would test tubes under conditions approximating their use in a radio set. Here it is. Try it out. See for yourself how this instrument can save you time in hunting for troubles and help you sell more tubes. Model 1500 is a Power Output Tube Tester with Neon Short test and shadowgraph line voltage indicator. Dealers Net Price . . . $36.67 For more information see your jobber. Send for catalogue to THE TRIPLETT ELECTRICAL INSTRUMENT CO. Bluffton, Ohio * tJfr ***** t ***** *l pMCiAWH1 feLECTRJCAX LN STRU MINTS Mai! Coupon for Details i TRIPLETT ELECTRICAL INSTRUMENT CO. Dept. RT-J Bluffton, Ohio, U. S. A. Please send me (check) More information 1501, 1500 1936 Catalogue information on Name Street City -State SERVICE NOTES-RIDER Using cathode-ray oscillograph * Ever since the start of the exploitation of visual alignment apparatus employing the cathode-ray tube, the matter of basic response curves to be used for comparison with the images appearing upon the screen, has been the subject of discussion. . . . What type of curve should be developed in the i-f. amplifier? . . . How can a serviceman align visually if he does not know the proper curve for the system? . . . These are the two leading questions hurled at men who speak about visual alignment. The problem is not as difficult as it appears. Standard response curves for comparison are valuable, but it is possible to get along within them, that is, if the operator is familiar with the various types of response curves which may be developed with tuned circuit of the variety to be found in radio receivers. Incidentally, this type of information is also of value to the man who does not possess cathode-ray tube type of alignment equipment and who is using the conventional meter type indicators. Basically, there are two types of response curves of interest in connection with alignment. One of these is the single-peak type of curve which results from loose or critical coupling of the circuits involved, and the other is the dual-peaked or even triple-peaked response curve which results from over-coupling of the circuits involved. As a general rule, the majority of i-f. transformers utilized in superheterodyne receivers, unless otherwise stated, are of the loose-coupled type and when properly adjusted develop a single-peaked response curve. However, it is possible to develop double-peaked response curves by over-coupling the two circuits, usually found in these transformers. I-f. transformers which employ three coils are usually over-coupled and develop multi-peak response curves, usually of the dual peak variety. Speaking in generalities, the response curve developed with a transformer is a function of the coupling between the circuit and the adjustment of the tuning trimmers. Units which are designed to develop a single-peak, when very accurately tuned have a sharp peak with steep sides. Incidentally, the steepness of the sides is a function of the efficiency characteristics of the unit. The more efficient the unit electrically, the steeper the sides and the greater the response to the peak frquency, which is the resonant frequency of the r^r: i r i 450 4?7 -46t> 46? 470 Fig. 1 — Unretouched photographs of cathode-ray patterns taken by John F. Rider, service editor of Radio Today 44 Radio Today