Motion Picture Herald (Jan-Mar 1932)

February 13, 1932 Motion Picture Herald 31 tain or restore the show. It is suggested, however, that the amplifier so replaced be retained in the projection room and repaired there; the replacement amplifier, being regarded, whenever possible, as in the nature of a loan, to be returned in a few hours. The part at fault is found by the conventional methods of testing for electrical trouble already mentioned. These involve the use of appropriate meters and circuit drawings. In most cases, it will be found advantageous to replace, rather than to repair the faulty part, since such parts are only seldom verv expensive. Occasionally the time involved in repairing such a part will be less than the cost of replacement, but this will prove the exception rather than the rule. Replacement of the defective part does not end the requirements of projection room repair. On the contrary, the amplifier must be thoroughly inspected and tested to make certain that no ulterior fault exists, which may have caused the breakdown of the part in question, and which will therefore cause any replacement of that part to break down also. Resistances commonly consist of a number of turns of resistance wire, which may be exposed, or may be baked into an enamel plate or tube. In the former case, a burntout section can be jumped by any suitable conductor ; in the case of the enamel-covered type, repair is impractical — and should not be attempted. Inductances consist of a number of turns of insulated copper wire wound around a core of iron or iron alloy. Rewinding the coil is too expensive to be practical, so that repair is inadvisable unless the burnt-out section happens to be confined to the surface layer. Some inductances are buried in tar, or some similar compound, and repair of these is wholly inadvisable. Both inductances and resistances occasionally are built in a number of sections, with individual contact points for each section. In some cases, not all of the sections will be in use. An unused section, if of equivalent electrical value, may sometimes be substituted for one which has burnt out. The transformer is substantially a double inductance, subject to the same considerations with regard to repair. Condensers may be of two types — "dry" and "electrolytic." The former, Avhen punctured, will sometimes — not always — heal itself. It will do this if the insulating material between the plates is of such nature that it will melt, flow into the puncture and seal it. A condenser of this type should not be thrown away until it has been tested at working voltage to make sure it has not healed itself. It can sometimes be made to heal itself by repeated exposure to working voltage. The electrolytic type can be repaired by being connected across a direct current line according to its marked polarity and at its rated voltage. The insulating film in the condenser will repair itself. An ammeter connected in series with the condenser will show current flowing until the repair is completed, after which current will no longer pass. PERFORMANCE COUNTS! and on this basis Distributed by Progressive Independent Theatre Supply Dealers mm SUPER HIGH INTENSITY PROJECTION LAMPS are preferred and used in theatres from coast to coast. Correctly engineered and carefully built. A demonstration will convince you. BREMKERT LIGHT PROJECTION CO. Engineers & Manufacturers • St. Aubin at East Grand Blvd. Detroit Carbon Prices Reduced EFFECTIVE January 1, 1932, substantial price reductions apply to all National Projector Carbons. Motion Picture Theatres will save from five to twenty-eight per cent on their carbon costs at these new prices. This announcement is in line with National Carbon Company's policy of sharing with the industry benefits derived from its program of intensive research and steady improvement in manufacturing methods. Use National Projector Carbons in your theatre. A sound investment in 1931. A better investment in 1932. NATIONAL PROJECTOR CARBONS , . . Sold exclusively through distributors and dealers, ISational Carbon Company will gladly cooperate with the producer^ exhibitor, machine manufacturer or projectionist on any problem involinng light, NATIONAL CARBON COMPANY, INC. Carbon Sales Division • Cleveland, Ohio Unit of Union Carbide MNM and Carb on Corporation BRANCH SALES OFFICES: NEW YORK PITTSBUReH CHICAGO SAN FRANCISCO Double Bearing Attachment For SIMPLEX and KAPLAN Machines Turn Your Old Style Single Bearing Into Double at a Saving of Over $100 on Each Movement Eccentric Takes Up Star and Cam Play, Same As CoiTiple+e As Shown, Only $35.00 in the Single Bearing. 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