International projectionist (Jan-Dec 1947)

AT YOUR SERVICE (Continued from page 26) about three hours, as it is necessary to remove the entire case. I have made the relay easier to service by mounting it on a Bakelite panel attached to the main terminal strip. I positioned it directly above the control shaft with three inches of the relay above the terminal strip. The heat at this point should not be excessive. It is necessary to run another pair from the 110-volt control contacts and to make a new three-wire cable to run from the terminal strip to the relay. The relay can then be serviced between reels. As I believe all these relays will eventually give trouble. I think the aforementioned change could well be made on all. Also, it might be wise to have a set of spare contacts. — F. A. Brown, ALTEC. Starting Failure of Delco A-202 Motor Considerable trouble was experienced with slow starting of the Delco A-202 motor used on Motiographs. The equipment was perfectly free and all mechanical alignment was such that no trouble should be experienced. The condition was satisfactorily corrected by replacing the 100-ohm starting resistor with 50 ohms.— C. T. Hoops, ALTEC. Matched Optics; Lamp Alignment The improved results we have obtained in a number of theatres verify the importance of matching the speed of the arc lamp reflector with the projector lens speed. Lamp manufacturers usually specify a definite working distance between the reflector and aperture, but unless the lens speed is F:2 or better the working distance must be varied to effect a proper match. We are convinced beyond doubt that the well-known "pin-hole" aperture method of lamp alignment will not necessarily align any part but the reflector itself* In the event one wishes to align, or check alignment of, the carbon holders, guides, or other lamphouse parts with the projector optical system, use the straight steel rod, or (and much simpler) a stretched string from the center of the full light image marked on the port shutter, back through the projector with lens removed, and on through the carbon holders. Check string for centering in the aperture and reflector opening. —J. A. Webster, ALTEC. Hum From External Light After trying new aperture plate, with hum still present from Technicolor prints, I finally found trouble to be caused by a reflection from porthole glass to top of 49 amplifier and thence to P. E. C. through hole in front of 1-type sound unit, which is used to give screw driver access to P. E. C. terminal binding post. Since P. E. C. is sensitive to red * IP concurs, having long decried the well-advertised "pin-hole" as an effective means for lamp alignment, trade paper "experts'* to the contrary. The use of a steel rod for this purpose, as advocated by the Projection Practice Committee of the SMPE in 1935, still is the best method. — Ed. light, only Technicolor containing reds, and not black-and-white or new Cinecolor, would give hum. Hum caused by interruption of light by shutter at a rate of 48 times per second. Some fun. — G. H. Hall, ALTEC. Clarifying U Base Lubricant A useful stunt which aids in clarifying the lubricant in "U" Base drives is to affix a small Alnico magnet bar to the oil drain plugs. The magnet can be held in place with ambroid cement and causes the drain plugs to attract small particles of steel and iron which otherwise would be contained in the lubricant. The plugs can be removed periodically and any adhering metal particles removed. A wooden plug can be used as a stopper during this process to prevent the grease from draining. (Magnetized drain plugs may also be obtainable at automotive service stations). — A. D. Turnbull, Bom. Sound Equip. Co., Canada. Hum in the 46 Amplifier In a recent installation of a Voice of the Theatre horn system with a 46-type amplifier, a high 120-cycle hum level was eliminated by replacing the 247-A input transformer with an Altec Lansing A-247-A transformer. The A-247-A must have an electrostatic shield between primary and secondary, although it does not show on the diagram. Try this where hum level is high. — F. S. Barnes, Jr., ALTEC. SIX-PHASE MEANS NO FLICKER Only "C&C Type H28 70 (70 Amp.) SIX PHASE RECTIFIER Other Capacities Available Offers You SIX-PHASE Full Wave Rectified Power (Actually equivalent to 12-phase half wave) MOTION PICTURE Theatres all over the U. S. and many Foreign Countries enjoy better projected light through rectified power from the new "C&C" SIX-PHASE Rectifiers. SIX-PHASE full wave rectification eliminates ripples and disturbing harmonics unavoidable in conventional three-phase rectifiers. The superiority of "C&C" SIX-PHASE rectifiers is universally recognized by experts in projection. This new development in motion picture projection is backed by over 15 years of research and engineering in the rectifier field. With progressive theatre owners the "C&C" SIXPHASE full wave rectifier is fast becoming standard equipment. For a more perfect light on your screen, investigate the "C&C" SIX-PHASE Rectifier. Quality Equipment Pays Off at the Boxoffice Write for complete information about the new SIX-PHASE Arc Lamp Rectifier DISTRIBUTED BY NATIONAL THEATRE SUPPLY McCOLPIN-CHRISTIE corp. LOS ANGELES 3 7, CALIF. Specialists in Rectifiers for More Than 15 Years CLAYTON BALL-BEARING EVEN TENSION TAKE-UPS For all projectors and sound equipments All take-ups wind film on 2, 4 and 5 inch hob reels. Silent Chain Drives THE CLAYTON REWINDER For perfect rewinding on 2000-foot reels. CLAYTON PRODUCTS CO. 31-45 Tibbetr Avenue New York 63, N. Y. INTERNATIONAL PROJECTIONIST • November 1947 35