International projectionist (Jan-Dec 1940)

This department is a collection of random thoughts and some not so random; fact, fancy and opinion relating to the man behind the man behind the gun — the serviceman. The prime purpose of this section is to promote a closer relationship between serviceman and projectionist based on a better understanding of their mutual problems through an exchange of news and views, kinks and kicks. To this end, contributions relative to any phase of the serviceman's activities are invited. VENTILATING problems are imminent; and, since experience is reputed to be a great teacher, the following is offered for the weal of projectionists and managers who have to worry about such things: One night last June I went into a theatre and found the place stifling, although it was equipped with a modern pressure ventilator. The manager said he had been complaining to his home office for seven weeks and that they decided an expert ventilation engineer was needed — "as soon as one was available." He had eight walkouts that evening, so I decided to look over the system myself. The system consisted of two drum-type fans in tandem arranged to draw cool air from outside in summer and with ducts and dampers to permit heating and recirculation in winter. While heat had been necessary the results had been fine; and the manager said that in 1937 when the theatre was built the cooling had been perfect. There were four speeds on the fans, but at the time the top speed produced only a faint movement of air. After the show I had the local electrician check the wiring, which was found to be OK, while I checked all ducts and dampers. Finally I crawled into the fan rcom and decided that the fans were turning in the wrong direction. Reversing one leg of the 220-volt, 3-phase supply gave proper rotation, and the system then functioned perfectly. The exhibitor was saved the expense of having an expert in on the job. We found afterward that a representative of the local electric company had been making demand load tests at the theatre in April, and we assumed that he had changed the leads while connecting his instruments. This drum-type fan is peculiar in that when it is reversed it continues to blow air but at a very low rate. — F. A. Brown, Altec, Boston. • • • Projectionists who are following the progress of television will be interested in R.C.A.'s new Iconoscope tube which will be known as the "Orthicon." This new eye for the television camera can see through a wide variety of lenses and under a wide range of lighting conditions. The "Orthicon" will enable the telecasters to pick up programs on a cloudy day or when the setting sun dims the scene. The problem of lighting the scene to be televised has been of major importance in the past. • • • It is frequently convenient to use a cork stopper in the film cement bottle. However, the mouth of the bottle and the cork stopper soon become coated with the dried cement, resulting in an unsatisfactory arrangement. If the cork is first coated with a thin layer of oil, it can be used for months without difficulty. Be careful not to get any oil in the cement. — W. W. Gilreath, R.C.A., Louisiana. [Note: Good stunt, but wholly unnecessary since introduction of new splicing liquid that neither discolors, hardens or thickens, requires no thinning agent, and retains its "oomph" down to the last drop. — Ed.] • • • Request for service stated: "Running on zero (volume control point) on one machine— still too loud. Other machine OK." It developed that this unusual condition was due to one of the output wires being grounded to its lead shield, thus shortcircuiting the volume control which fed the full output of the machine into the main amplifier. — Pete Case, Altec, Newark, N. J. • • • Every projection room equipped with Simplex projectors should carry an extra Gil 2 gear. This gear would be the first to strip in the event of a bind-up in the mechanism. The G112 gear is a mechanical fuse in a gear circuit, so to speak, and a spare should be on hand at all times. — C. B. Zimmer, R.C.A., New Jersey. m • • Who hasn't had trouble with noisy rheostats, particularly on the old-style systems using direct current for vacuum tube filament supply? I have had more success in eliminating rheostat noise by connecting an electrolytic condenser directly across the terminals of the filament rheostat itself, than by connecting the condenser directly across the power supply, as is the usual practice. — R. P. Egry, Altec, Pittsburgh. • • • More cold weather news relative to the tolls exacted by old man winter. This is a case of a "delayed" trouble. At the Colonial Theatre, Moravia, N. Y., the sound system was badly damaged and inoperative due to events as follows: Cold weather froze and broke the pipes of the sprinkler system in an upper floor of the building. Nothing happened until the pipes thawed out and began to leak, when water ran down onto the sound equipment. — G. A. Brown, Altec, Syracuse, N. Y. • • • Extreme care should be exercised when installing any a.c. type arc lamp, in order to prevent hum pickup in the sound system. The proper ground should be installed and particular attention given to loose connections in order to prevent circulating currents. Wires carrying a.c. oi pulsating d.c. should be twisted whenever possible. The field set-up by parallel a.c. leads are the source of many hum troubles. — S. H. Schultz, R.C.A., Washington, D. C. Oil collects dirt, deteriorates insulationon wires, impairs the efficiency of a lens system, and is one of the most frequent causes of inferior sound. M. A. Walsh, R.C.A. Field Engineer in the New York district says that the best way of preventing excess oiling is to use an oil can with a small spout from which you can place oil in a bearing at will and in definite quantities of one or two drops at a time. Excess oil should be wiped off frequently and absorbent pads used at the base of the projector head. — M. A. Walsh, R.CA.r New York City. • • • The best place to store a spare fuse isright beside the fuse receptacle, or tied tothe receptacle. When a motor refuses to start, try spinning it by hand while the current is on — the centrifugal switch may be stuck. Any apparently minor sound troubles should be noted on a slip of paper and reported to the sound engineer on his next call. Troubles which have apparently corrected themselves will be of particular interest, since these troubles may indicate the development of a major defect. Be sure to write it down, as these minor troubles experienced are often forgotten. Every projection room should be equipped with a first-aid kit and chart. — M. B. Faige, R.C.A. , Boston. MARCH 1940 25