Motion Picture Herald (Jan-Mar 1932)

30 Twenty years of rehearsing ought to make any act perfect — and LeRoy Sound Equipment has twenty years of study and experiment behind it. It's sure-fire payoff. Embodies every feature that a projectionist could demand, and the one feature that every owner says is indispensable — moneymaking. Ruggedly designed ; built of finest materials by most skillful men ; nothing haywire about LeRoy. Ball bearings where the friction comes — chrome plate, harder than steel, where wear falls. Film edge guide adjustable for wear in one second ; renewable in one minute. Easily installed; easily operated; easily paid for out of extra profits. Models for Simplex, Powers and Holmes Portable Projectors. Money-back guaranty if unsatisfactory. Write for details. 421 LYELL AVE., ROCHESTER, N. Y. Affiliated with Octo Engineering Association, Inc. Replacement parts for Powers Simplex Projectors 15 years experience in building precision machinery and motion picture parts enables us to guarantee your complete satisfacticni on gears, sprockets, film rollers, studs, shafts, screws, springs, etc. Any part sent for inspection at our expense. Write for our new catalogue listing over 1,5(X) different parts. Ask about our special discount to reputable firms. Qualityprice — service. Vou can't beat it when it's from Motion Picture Machine Co. C. F. HUSSEY, Pres. 3110 Lisbon Ave. Milwaukee, Wis. Better Theatres Section Parts for mechanical repairs are commonly obtained to best advantage from the manufacturer of the drive assembly. Occasionally the local machine shop will be able to duplicate a simple part more reasonably, and very often more quickly. The manufacturer's part, however, will usually be less expensive, having been made in some quantity, and it should generally be more reliable. The advantage of the local machinist will be largely confined to the time factor. Disc Producer Projection room repair of the disc reproducer is in general inadvisable, and this is especially true of the oil-filled types. But in all types, a slight injury to the armature destroys the usefulness of the device. In general, the most economical practice would be to keep a spare reproducer on hand and to make no attempt at projection room repairs. When unavoidable, such repairs should be undertaken only with as much care as if the reproducer were a fine watch. Lens Assemblies Lens assemblies are of several types, each of which presents somewhat individual problems of trouble and repair. Perhaps the most common trouble of these assemblies is loss of adjustment (owing to vibration of the projector), which results in reduced volume at higher frequencies. Adjustment may be lost in two ways: The lens barrel may move forward or backward, impairing the focus ; or it may rotate slightly, in which case the beam of the exciting light will not be horizontal where it crosses the film, and both quality and volume will suffer. A few lens assemblies are so mounted that they can be adjusted without special tools, but in most cases a separate jig made for the purpose will be required. For although lens adjustment can often be effected by hand, it is a time-consuming process, in which half a dozen or more attempts will fail before one that is even moderately successful has been achieved. A volume indicator and a multiple-frequency reel are neccessary adjuncts to any attempt at readjusting the focus of slit assemblies. Successive adjustments are tested by means of the film and the indicator until one is reached that gives a satisfactory response curve. Time can be saved if a high-frequency loop is available. In that case only a single run need be made with the multiple-frequency reel. This will indicate the degree of high-frequency response necessary for a satisfactory adjustment. The high-frequency loop is then threaded and run continuously until the indicated response has been reached. Lens assemblies are also subject to oil leakage— volume falls off sharply if even a small amount of oil finds its way inside tliis assembly. Dirt collecting on the inner portions of the lens tube also leads to loss of volume, and sometimes to noise as well. AL-my lens tubes can be disassembled in tlie projection room for cleaning. If they are liandled carefully, no harm will result, provided the frequency film and the volume indicator are available for checking adjust Febriiary 13, 1932 ment after they have been restored to service. But wherever instrumental check is not available, or careful handling is not assured, it will be safest and least expensive to have the tube readjusted by its maker. Ordinary sound and the human ear will not replace the frequency-film and the indictator. The ear may report the sound as unsatisfactory, but it will not be sensitive to extremely small changes in quality, and therefore it will not be able to report whether any small step made in adjustment is a step in the right or in the wrong direction. For that purpose, the instrument is indi'=pensable. Faders and Switches SWITCHES OF THE type in which contact points are carried upon long, slender prongs, occasionally cause trouble when the prongs become bent or otherwise lose proper tension. Such prongs can be readjusted l)y means of a suitable tool, the action of Avhich can, perhaps, be best described by saying that this tool "combs out" the prongs, straightening them. In the absence of such a tool, adjusting prongs of this type is so difficult as to be sometimes nearly impossible, and almost always inadvisable. Resistances of the type commonly used in those faders that function as volume controls, occasionally burn out. A burnt-out resistance of this kind is not amenable to projection room repair. It should be replaced, if a duplicate can be obtained ; if not, the fader should be returned to its maker. Sometimes, however, it may be possible to secure a resistance of somewhat different design but of equivalent electrical value. Contact studs of faders, or other volume controls, not infrequently cause trouble because of the amount of wear to which they are subjected. It may happen that the contact fingers, in touch with these studs, groove them in such fashion as to make perfect contact more and more difKcult as time goes on. Occasionally it Avill be possible to have a local machine-shop make up a contact arm of somewhat different design, which will brush the stud over a larger area, and so prevent grooving. This is a simple precaution that may prolong the useful life of a fader or volume control to several times that of its normal expectancy. Amplifiers The electrical apparatus combined in an amplifier most commonly includes one or more transformers, tube sockets, condensers, reactances and resistances. Any of these constituent parts may, by breaking down, prevent the amplifier from functioning. In most cases of amplifier trouble not more than one or two of these parts will be found at fault ; only on rare occasions, several of the parts ; practically never, a majority of them. Replacing the part at fault is obviously less expensive and less troublesome than replacing the entire amplifier and returning it to its maker for repair. \Vhen the trouble cannot be located quickly, it may prove desirable to replace the amplifier by another in order to main