Sound motion pictures : from the laboratory to their presentation (1929)

MAINTENANCE AND INSPECTION 183 primary and the secondary windings. If a click is heard only when the contact is made the transformer is not leaky, since such a sound is caused by the momentary change of charge in the windings and the accompanying rush of current through the phones. Short circuits between the windings of a transformer may result from contact of the internal leads and the lugs. A grounded condition may be caused if these leads touch the transformer shell. Such trouble is usually brought about by the loosening of the locknuts on the terminal screws, permitting movement of the leads. Most wellmade transformers do not develop such trouble, since the internal leads are well insulated. A complete short circuit of the B battery may result if there is a direct path for current to flow across the primary and secondary windings. To test for such a condition, touch one of the testing tips successively to the shell of the transformer and the other to the terminals; when they are in proper condition no click should be heard; a distinct click indicates a short circuit. The trouble can usually be remedied by removing the shell and providing insulation on the leads. A similar trouble is experienced when the soldering lugs, attached to the terminals on the outside, are accidentally bent down so that they make contact with the shell. III. R. C. A. Sound-Projector Systems To insure proper operation the projectionist should inspect and check the equipment (daily and weekly) as follows : I. DAILY INSPECTION AND CHECK A. Projector and Reproducer The projection machine should be given the usual attention. All rollers and friction wheels in the reproducer head must be cleaned twice a day, by means of a lintless