International projectionist (Jan-Dec 1950)

is 5/16 inch, which space may be easily measured by using a 7-mm negative carbon as a gauge, since the 7-mm is practically 5/16 inch. The diameter of a 7-mm negative should just touch the tips of both carbons as it is passed through the arc gap, preferably just after the arc has been extinguished after a 20-minute run. By adjusting the motor feed to maintain the 5/16 arc gap length, you can increase the arc amperage as high as you want to with the ballast rheostat. Drop in Line Voltage Of course, if you have low d. c. voltage, that will also cause the amperage to be low. In measuring the d. c. voltage, the readings must be taken in the projection room and while the arcs are burning. To measure the voltage at no load, as you said you did, is of no value, because a drop in line voltage only occurs when the load is on: no load, no loss of voltage. A drop in line voltage occuring when the load is applied indicates either too small wires or a very long run of wiring to the projection room; in other words, too much resistance in the wiring. Of course, a small drop in voltage is to be expected, but if the voltage falls to 105 or less when the arc is burning, it is an abnormal condition which may be corrected only by cutting out some of the rheostat wire, as explained previously. To provide for the occasional job where the voltage is low, and when we have not been advised of such a condition, we have purposely built the rheostats so that it is a very simple job to cut off some of the resistance wire. Projectionist Examination Questions From time to time IP receives requests from Local Unions and from individuals for a list of questions which are used in examinations for a projectionist license. Appended is the first group of such questions, with others used in various localities to appear in subsequent issues. 1. The color of the label of a the film speed is 90 feet per minute, N.E.C. fuse rated at 250 volts and 60 frames will pass by the aper amperes is.. ture in one minute. 2. The stamped rating of a link fuse is always per cent of its actual rating. 3. Carbons used for projection service usually have their diameters expressed in.... and their lengths in 4. That type of insulation which is used on arc jaws is called insulation. 5. Nitrocellulose film is known as film. Another interesting situation is reflected by the appended exchange of correspondence: To Strong Electric Corp. I have a pair of LOU-5 Stiong Utility lamps with which I have been experiencing quite some trouble. When I throw-in the lamp switch the motors run O.K. As soon as I strike the arc the motors immediately go into reverse. This reverse action is especially marked when I am burning-in new carbons. After the carbons are burned-in well the motors work O.K. Occasionally the same reverse action sets in when I am burning buts in carbon savers. Reply To Projectionist The LOU-5 Strong Utility is rather an early model lamp which if operated at the high amperage that is common today may result in the control motor being a bit too sensitive. To overcome this difficulty by reducing the sensitivity of the motor, it is only necessary to shunt the armature with a 200-ohm resistor. We are sending to you, without charge, two of these resistors on mounting strips and with the connecting 6. There are frames to every foot of 35-mm film. 7. 35-mm professional film is threaded into the machine so that the film is 8. On a professional projector the distance from the picture aperture to the sound aperture is inches or frames. 9. A rheostat is rated at 1250 watts and has a resistance of 2 ohms. This rheostat may carry, at rated conditions, amperes. 10. An imaginary straight line passing through the exact center of a lens or of all the elements of an optical system is called the 11. In a 35-mm machine in which 12. In cementing lens elements together one usually uses 13. The black or opaque overlay on the sound track at splices is called 14. A wire which has a circular cross-section and a diameter of 1/1000 inch will have a circular area of 15. That device which instantly cuts off the light from the film and on the screen is called 16. That light source which supplies light to the photoelectric cell is called the 17. One thousand cycles is also called a 18. That device in a projector head which causes the film to remain stationary in the gate is called the 19. The openings in the front wall of a projection room through which the light from the projection lens passes are called the 20. That blade of a rotating shutter which covers the projection lens while the intermittent sprocket is in motion is usually called the [To be Continued] wire. The attached blueprint shows how they are to be mounted and connected. If after installing these resistors you continue to have trouble, do not hesitate to advise us, indicating the size carbons used, the arc amperage, and the type and make of your generator or rectifiers. Loew's Greater Profit in 1949 Despite a decline of $6,475,400 in operating revenues, Loew's, Inc., in the year ended last Aug. 31 had a net income of $6,744,761, greater by $1,435,102 than the $5,309,659 net in the previous fiscal year, company reported. Additionally, an interim report for the 12 weeks ended Nov. 24 shows a net profit after taxes of $1,652,649, equal to 32 cents per common share, compared with a net of $1,021,156, equal to 20 cents per share, in the first quarter of the last fiscal 12 months. Earnings for the recent fiscal year are equal to $1.31 per share, as compared to $1.03 per share in the year ended Aug 31, 1948. Bausch & Lomb Executive Changes Bausch & Lomb Optical Co. has announced the election of President Herbert Eisenhart as Chairman of the Board. President of the company since 1935, Eisenhart will be succeeded by Joseph F. Taylor, whose former post as Treasurer will be filled by William McQuilkin. INTERNATIONAL PROJECTIONIST MARCH 1950 13