International projectionist (Jan 1941-Dec 1942)

exposure to heat in a boiling out of the tar, which bubbles or oozes out of the case of the condenser. This loss of resistance material in the interior alters the capacitance, and in time may reduce the internal resistance to the point where a flashover and burn-out can occur at normal operating voltage. Condensers which are losing tar to any serious degree should be replaced. Coils and Transformers Over-hot operation is the principal external sign of impending trouble in these parts — but it must be remembered that many power transformers and some filter chokes are intended to and do operate hot. Here is where a thermometer is particularly useful, since the manufacturer can designate the same temperature rise of a given transformer. When this is exceeded, the cause may be external and lie in undue rise of the applied voltage; but it may also be internal and consist of a short-circuit of some turns of wire, resulting in increase of current flow. Finally, the cause may also be external in the sense of lowered resistance of some part in series with a choke coil, or in a shunt to a transformer secondary. It is often impracticable to open a transformer to inspect the condition of its coils. If all external conditions are checked and shown to be normal, if ventilation is checked and found normal, the coil is commonly considered at fault. This may finally be checked by installing a replacement and observing whether it operates at normal temperature. Ohmmeter tests of the transformer windings will disclose any glaring short-circuit; but one that results only in decrease of the inductive reactance may not be very evident to an ohmmeter check. However, every recourse is exhausted before a large power transformer is replaced. They are expensive, and, being expensive, are so built that they very seldom cause trouble. Suspect everything else first. A somewhat more common fault in transformers and chokes is loosening of the bolts that hold the core laminations together. If the laminations are loosened enough to allow them to vibrate, hum in the reproduced sound will result. The remedy is physical inspection and tightening of the bolts as soon as slight hum. due to this cause, appears. The smaller models are held together by rivets, not bolts, and do not produce trouble of this kind. Sockets may give trouble by loss of the spring tension with which they make contact to the prongs of the tube. Poor contact may produce noisy sound, or even in some cases sparking between prong and socket contact. Dirt in the socket will produce similar results. Whenever a tube is suspected of being noisy, or shows signs of it on tapping the tube, the socket also should be suspected. Inserting and removing the tube three or four times will usually clear any dirt in the socket; the prongs of the tube may be inspected and cleaned with carbon tetrachloride or very fine sandpaper — not emery. If the spring contact has weakened [less likely in new socket types] the socket may have to be replaced. Noisy sound is the warning. Another trouble of some socket types is breakdown of the material on which the contacts are mounted, much in the same way that some resistor cores break down under the heat of prolonged operation. Any undue difficulty in inserting or removing tubes, or any undue shakiness of the tube in its socket, whether noisy sound follows or not. calls for inspection of the socket insulating material, and prompt replacement of the socket if any fault of this kind is found. Wires and Insulation Prolonged exposure to heat may cause deterioration of thin strands of copper wire, depending principally on industrial gases that may be present in the atmosphere. Sulfurous gases, for example, are harmful to copper wire. Signs of blackening of exposed strands call for • relatively frequent inspection and, possibly, replacement of the conductor. Prolonged exposure to high temperature may produce crystalline changes in copper wire, making it brittle rather than flexible and leading it to break under conditions of even moderate vibration. Exceptional stiffness in a thin copper wire is a warning sign, indicating thai an open circuit may follow at some time or other and that replacement of that wire or of a section of it may be desirable. Heat also causes some types of rubber insulation to become hard and to crack, exposing the conductor. Where this condition is found in a location making shortcircuit possible because of exposure of the wire, replacement is indicated. Oil on rubber insulation calls for replacement more frequently. Many types of rubber will deteriorate, with resulting possibility of noisy sound. It is somewhat common practice, where this condition is found in a sensitive part of the sound system — a part followed by much amplification — to consider oily rubber a warning of noisy sound to come, and to replace it. 4V2 MILLION WARNER PROFIT Warners and subsidiary companies report for the 39 weeks ending May 31, a net operating profit of $4,433,445 after deducting all charges including amortization and depreciation, a provision for contingencies amounting to $914,000 and normal Federal income taxes, as compared with a net operating profit of $2,450,713, after a provision of $175,000 for contingencies, reported for the corresponding period the previous year. Earnings are equivalent to $4.50 per share on 99,617 shares of outstanding preferred and, after allowance for current preferred dividend requirements to $1.12 per share on, 3,701,090 shares of outstanding common. Preferred dividends in arrears amount to $33.68 per share. Recent installation of Simplex High 1-kiv. lamps in the Tivoli Theatre, Mishawaka, Ind. Room is presided over by Truman D. Rogers, LA. Local 187. AUGUST 1941 11