Theatre Catalog (1946-47)

tory results are obtained from operation at the normal rated values. Amplifiers using the large type power tubes, and if not equipped with a timedelay, pre-heating relay, require preheating of the filament element. This type of amplifier is usually provided with a filament-plate switch. The tubes should always be allowed to warm up 5 to 8 minutes before closing the plate current switch. The tube contacts should be kept scrupulously clean. This will prevent poor contact which may result in intermittent noise or loss of sound. A spare phototube should be stored in a cool place. Exceedingly high temperatures may cause the volatile cathode surface to evaporate and the cell to lose its sensitivity. The phototube anode voltage should be maintained within the manufacturer’s specified limits. Operating phototubes with the anode voltage above normal may cause the tube to ionize, which will result in permanent damage to the tube. Avoid exposure to direct sunlight or projection arc, as this may decrease the phototube’s sensitivity. If the equipment uses mercury-vapor tubes, keep them in an upright position at all times after they have had their initial pre-heating. If possible, keep all spare tubes in their original packing cartons to prevent breakage. If a tube has to be removed from some part of the equipment, do not discard it immediately. Let the service engineer make a thorough test to determine if the tube should be discarded or if it can be used in some other part of the equipment. Very often a certain tube can be usd in one place where it cannot be used in another. Exciter Lamps All spare exciter lamps should be stored in the spare parts cabinet. Exciter lamps should not be dropped as the filament may be damaged or bent out of position. Avoid too much tension on the lamp base, if used with a screw tightening exciter lamp holder, as it may crack the glass envelope. After the service engineer has determined the proper exciter lamp voltage setting, it should not be changed unless some emergency expedient requires this to be done. It is extremely important not to operate the lamps at a voltage higher than rated, as the useful life will be greatly decreased. Soundheads The mechanical parts comprising the soundhead are machined to very close tolerances, because of the delicate and precise function they must perform. Improper adjustment, lack of oil, improper lubrication and lack of proper maintenance all have a tendency to decrease the life of each moving part. All moving mechanical parts and bearings should be properly adjusted and lubricated. Excess oil should be wiped off after each lubrication, Optical Systems All soundheads should be kept absolutely clean and free from oil. If necessary, small absorbent pads should be placed above the optical unit to soak up any excess oil. Most soundhead optical 324 units are sent in for repairs because the lens barrel is partially filled with oil. The soundheads should be wiped out periodically, using a cloth saturated with carbon tevrachloride or similar solvent. The lens elements may be cleaned with lens tissue and extreme care should be taken to avoid scratching the lens surface. Projector Mechanisms Projectors or soundheads should not be allowed to operate with excessive vibrations. When a machine vibrates excessively, it is a sure indication that some component part is not functioning properly. Unwanted projection room noise and poor screen results will be gradually increased if causes for vibrations are not located and corrected. Vibrations in one part of the assembled projector can lead to serious troubles in other parts, until the machine will eventually break down. NOTES ON PROJECTOR CARE Dirt has been the cause of serious film fires in preventing the proper operation of the automatic fire shutter or in clogging the fire-valve rollers. It makes them susceptible to wear and renders them useless for the purpose intended. Dirt may also cause the stoppage of sound reproduction by accumulating on the various movable contacts or on the vacuum-tube contacts in the sound equipment. It may cause losses in screen illumination, when deposited on the projectionare reflector or condensers, and has resulted in the rapid deterioration of carbon contacts with communicated damage to the adjacent parts of the lamp mechanism, Dirt on the gear teeth and shafts of the projector, combining with lubricating oil, acts like a grinding compound, causing excessive wear and shortening the effective life of the gears and bearings. On fuse clips, dirt causes high-resistance contacts and the generation of heat which may sometimes cause the fuse to blow. Make sure that the lamp house and all parts are kept thoroughly clean both inside and outside. The carbon ash, drippings, and so forth should be removed regularly once a day, especially from the shafts, bushings, and gears of the arccontrol-operating parts. The are-exhaust dampers and ducts should be cleaned frequently of carbon ash, dust, and so forth. Any blockage, no matter how small, will affect the proper burning of the carbons, cause pitting of the mirrors, and produce a gradual accumulation of ash within the lamp house. If there is a filter in the airsupply system, make sure it is in efficient working order. Care should be taken to prevent dust and dirt from blowing into the projection room through any windows if left open, Motor-Generators To get the most out of motor-generators, they should be kept clean and all dirt should be removed before sparking becomes disastrous. Increased brush life, as well as increased commutator life, will be the direct result. P Dirt on commutators causes arcing and pitting, shortening their life, increasing maintenance costs. The contacting surface of each commutator brush should be examined periodically so that the commutator and bearing wear is held to a minimum, If the generator is on a concrete floor, care should be taken in sweeping, so that abrasive dust from the concrete will not get into the bearings. Projection Room The exhibitor who is interested in keeping his projection maintenance costs low should extend to the projection room the same services used in cleaning the auditorium and other parts of the theatre. The projection room floor, walls, and ceiling should be of such materials that will not dust off. If the floor is of exposed cement, it should be kept well painted with dust-proof or sealer paint, and should be mopped frequently. A supply of lintless cloths for cleaning should be made available, as well as other cleaning facilities, such as carbon tetrachloride, brooms and dust pan, metal waste can, and the like. In fact, these should be standard equipment of the projection room. A stiff-bristled toothbrush is useful for keeping the sprockets and idler roller clean. The space between the fire-valve rollers and the castings in which they are mounted can be easily cleaned by inserting a narrow strip of film and drawing it back and forth to dislodge any dirt. Lubrication Always follow the manufacturer’s instructions and use only the grade of oil recommended by the manufacturer. The importance of lubrication of projection equipment cannot be over-emphasized, Projection equipment lubrication carried out properly and under the manufacturer’s instructions will lead to troublefree operation. The use of the proper types of oils and greases and their proper application will give longer life to equipment and keep standards of projection on a high plane. Rules for Lubrication Strict adherence should be made to the following rules: (1) Do not lubricate the mechanism while it is in motion. Doing so is haz ardous to both the mechanism and to the projectionists. (2) Do not over-lubricate. Excessive lubrication is costly and wasteful. It also impairs the quality of the sound and of the picture. Only small oil cans which dispense small quantities of oil at a time should be used. . (8) Cleanliness in conjunction with lubrication is an important matter, simce excessive oil deposits promote the collection of dirt, dust, and grit on the vital parts of the projection equipment. Should the fire rollers become coated with oil, they will collect dust and grit, which will scratch the emulsion on the film. Such marring and destruction of film is very costly, and definitely contributes to no good. THEATRE CATALOG 1946-47