Motion Picture News (Oct-Dec 1930)

November 1 , 193 0 Motion Picture N e iv s 93 Problems of Sound in The Projection Booth Thoroughly covering that all-important topic: sound projection by means of an easily understood self-quiz for theatre managers, compiled by the Sound and Projection Department of Paramount-Publix Corp., Harry Rubin, managing director. Q. If, with a universal base there was no sound on disc, one machine okay, other machine and both movietones okay, and charging reproducer did not help, where might the trouble be and what could you do to keep the show running? A. Look for loose connection on 700-A apparatus unit or dirty connections on the film disc switch and disconnect 7-inch equalizer. Q. If, with two units, one unit blows out, and sound from the other is not enoueh to fill the house — what adjustments would you make to obtain additional volume? A. Raise the horn setting on the horn control panel to zero for the remaining unit to restore unity impedance until defective unit is replaced. More volume could be obtained by running fader at higher point. Q. Suppose volume on Red movietone had been slowly getting bad, and then suddenly went very low and noisy, where might the trouble be and what could you to do to keep the show running? A. Change P. E. cell and change tubes in film amplifier. Change "B" batteries or a poor exciting lamp. Q. Sound seems distorted. Sustained notes irregular. What is the trouble and where would you look for it? On disc? On film? What could you do to repair it? A. Flutter. On disc — rubber connector holding rings loose or Bristo set screws holding connecting shaft loose. On film — take-up out of adjustment. Take-up chain too loose, or leather disc on take-up worn. Loose tension holding film to sprocket or guide rollers, or defective projector fly-wheel. Accumulated dirt on face of sprocket in sound gate. Avoiding a Jam WHAT would you do if sound stopped suddenly on your disc sound machine while the other remained okay ? Or if your motor went badly off the proper speed ? Would either of these emergency situations jeopardize business, or have you a sufficient knowledge of the minor mechanics of sound apparatus to safely bridge the "jam" until arrival of a repairman? Every theatre owner and operator in the country should be fitted with a "surface" knowledge of projection apparatus to assure continuance of programs when trouble arises. A close study of the accompanying article will give to exhibitors the fundamentals necessary. Q. Light of exciting lamp as seen on paper when used for focusing, is yellow all over, focus apparently correct. Changing exciting lamp doesn't help. What is the trouble? A. Dirt or oil on optical assembly. Q. If while playing, disc sound stopped suddenly on one machine, while the other machine remained okay, what could you do to keep the show running? A. Look for a loose connection in 29-A connecting block or at Fader and change reproducer. After show it will be well to replace reproducer and test to see whether same is O. K. Q. If there was a bad hum in the movietone on one machine only and you could not hear in your monitor— what might the trouble be and how could you eliminate it while the other machine was running? A. The only noise that cannot be heard in the monitor as well as in the stage horns is pick-up of the noise made by the projector. This is a mechanical pick-up which can usually be eliminated by clearing the movietone amplifier where it is touching some portion of the casing. Check to see there is no bind in floating shaft. Q. If your 42A amplifier read 60 and one 43-A read 120 and the other 43-A read 100, would you suspect any trouble, and, if so, what would you do to prevent interruption to the show ? A. Replace 211-E vacuum tube in 43-A amplifier that had reading of 100. Test is made by removing one tube at a time and noting meter reading. Q. If your motor went badly off the proper speed, how would you remedy the trouble? A. Replace V-3 or V-4 with 205-D vacuum tube in control cabinet. Q. If your 702 type fader went bad on both sides, at all settings and every key position, and you could not repair it or get a new one immediately, what could you do quickly to keep the show running? A. Use a double-pole double-throw switch for the fader connecting the fader output to the blades of the switch and connecting a pair of head phones in series with switch blade as a compensating resistance. The output from each projector is connected to opposite ends of switch. Q. If sound stopped suddenly on movietone, meter on movietone amplifier read zero, what would you do to keep show running? A. Replace 239-A tubes in 49-A movietone amplifier or fuse on charging panel. Check for loose connection in F battery line. Schooling the Manager T 7 SED extensively by one of the biggest theatre chains in the country, the accompanying questions and answers on sound projection offer to every exhibitor an easy route to a thorough knowledge of every-day problems concerning successful operation of talking devices. Minor breakdowns or slight interference in the mechanics of reproducing need not command the services of outside sound engineers if exhibitors thoroughly acquaint themselves with the material presented herewith. It is suggested that the chart be constantly kept in the projection room so that ready reference may be made to it as occasion arises. Q. If 43-A amplifier meter needle dropped to zero and smoke issued from amplifier, what would you do to keep show running? A. — With only one 43-A in system? B. — With two 43-A system? A Strap output of 43-A on input of 43-A. Raise fader to 15 and gain control on 43-A amplifier to 23. Q. If needle was constantly skipping the groove, what would you do to keep the show running ? A. Start reel again with new needle and record on another proj ector and check level of reproducer arm and turntable before starting another reel on projector causing the trouble. Q. If a noise like a motorboat exhaust developed in movietone, how might you get it out while the show was running? A. Turn set-screw and upper guide roller first one way and then the other until sound is eliminated as this is caused in most cases by either frame lines or sprocket holes running where sound track should be. Q. If sound stopped suddenly and both meters on the 41-A amplifier read zero, what would you do to keep the show running? A. Replace three new tubes in 41 amplifier. If this does not correct above condition, replace film supply fuse with six-ampere fuse. This is located in the charging panel. Q. Suppose a crackling noise heard on both film and disc in one machine, but not heard at all on the other machine, what could you do to clear it while the show was running? A. Throw fader key to cut out faderr and clean fader. Leather Seats, Minus Wood, To Deaden Sound Spokane, Wash. — J. Knox Strachan, manager of the RKO Orpheum, states the house will be entirely remodeled and renovated. The house will be reseated with a new type of leather seats, especially built without wood to clafify sound projection. HeywoodWakefield are designing the seats for all RKO houses. New Simplex projection machines are to be installed, with high intensity lamp houses and a larger screen, which will insure greatly improved visibility and sound. The new marquee recently put in place is to have a change of lighting effects. The work will in no way interfere with operation.