International projectionist (Jan-Dec 1947)

-^TTT-.-T-T — .—^-.r-. YOUR SERVICE This department is devoted to the man behind the man behind the gun — the serviceman. Its prime purpose is to promote a closer relationship between projectionist and serviceman based on a better understanding oi their mutual problems through an exchange of news and views, kinks and kicks. Contributions from both groups are invited. Protect Sprocket Puller With Thumbtack A thumbtack inserted in the sprocketretaining screw hole of the 208 reproducer sound shaft makes a good bearing surface for sprocket-puller screw, when sprockets are stuck and have to be pulled off. Convex construction of tack head makes it strong, and it won't spread or bind in the sprocket or the shaft. — R. M. Porter, ALTEC. Faulty Tube Contacts I have found that in cases where there is continuous trouble with tube prongs corroding and flattening out, it is due to socket contacts rather than the mateteriel in the prong tips. Arcing generates heat, melting the solder on the tips. Where there is arcing one will generally find corroded and pitting socket contacts. Not news, this, but with good contacts there is no prong trouble. — Louis Wolff, ALTEC. Inspecting Tungar Bulb Filaments In order to prevent eyestrain while examining tungar bulb filaments, a projectionist I know mounted a piece of colored glass within a frame formed by a piece of wire. I snitched the idea and now carry this item in my regular tool kit.— W. V. Howard, ALTEC. Reducing Flutter on Universal Base Projection angle would seem to bear little if any relation to flutter, but I am convinced that it does. Every time a system with little projection angle was modified for power and Lansing horns the same trouble developed. Using the flutter bridge, I got a little reduction here and there by replacing sprockets, etc., but the trouble hung on, especially with Technicolor film not clinging to the sound sprocket. Observing that this difficulty held true only with equipments having 5° or less projection angle, I finally eliminated the trouble with a nickel's worth of washers and pushed the film chute another l/8th inch or better toward the sound sprocket. In six months there has been no recurrence of this flutter trouble in three theatres that previously were plagued by it. I think my simple remedy licked the problem.— W. S. Welshonce, ALTEC. Exhaust Fan Affects Reflectors? A projectionist was having difficulty keeping bis reflectors from fogging. The reflectors were very hot. The arc norm ally pulled 65 amps, but in order to overcome the extreme heat the current was reduced. Of course, picture quality was impaired. Investigation revealed that the exhaust fan was filled with carbon dust, the blades being coated even though the damper was wide open. A screen in a gooseneck of the exhaust pipe was entirely plugged with carbon dust. A general cleaning of the parts involved resulted in satisfactory operation with the damper only partially open ; full current was restored to the lamps, the picture image was improved, and everybody is happy.— H. M. Steele, ALTEC. Testing Condensers in D-96101 Filter In order to facilitate the testing of condensers in the D-96101 filter, I have made the following modification: five terminals are installed at the top of the terminal strip, as illustrated. The cable form of four leads, which now goes to the positive terminals of the four condensers, is pulled back and connected to the four terminals at the left; the terminal at the right is connected to the 90-volt terminal. This latter terminal is for connecting negative leads of condensers with pigtails when this type replacement condenser is used. New leads are brought out from the condenser positive posts (or the red ™"\pA \q/\ iSA >2^ i'TU3 t'BLK ;.WH '.BL § i 0 Isl (oj s — 44ov-t + + — ' > 90V 1 u I 90 V 90V a wire on condensers with pigtails) and are connected under the screws of the new terminals. By merely removing these wires from the screw terminals, the condensers are disconnected for testing without the necessity of removing the filter chassis from the cabinet. This eliminates repeated bending and heating from soldering of the lead cable of the 90-volt circuits. — R. P. Egry, ALTEC. Substitute RCA 6C6 Tubes On the early production of Motiograph pre-amplifiers they used W. E. 310-B tubes. The middle tube has high cathode potential and will occasion hum if the least bit leaky to the heater circuit. The installation of RCA 6C6 tubes will improve this condition materially. Then again, if the pre-amplifier is installed with other than Motiograph soundheads, or on other heads not having a resistor from the p.e.c. cathode to ground, much difficulty is experienced. The installation is noisy, and after the mechanism is started the volume drops considerably in about two seconds. This is due to the limited action at the preamplifier in the absence of a resistor to ground. The p.e.c. cathode feeds the .05-mfd. capacitor direct, which soon charges up. The 2.2-megohm resistor to ground is needed to remove this charge. It may be installed at the low-capacity cable connection in the pre-amplifier. — H. H. Quackenbush, RCA. Adjusting Reel Tension Without Gauge Needless to say, considerable film is damaged and sprockets are prematurely worn due to excessive film tension. Perhaps one of the most simple and practical methods for adjusting the lower takeup for proper tension is to proceed as follows : 1. Place a full reel in the lower magazine. 2. Adjust the tension nut until the reel will barely pick up speed with the machine. It may be necessary to repeat several times before proper adjustment is attained. When this is properly done the film will not be subjected to excessive tension, yet at the same time will eliminate all possibility of piling-up of film in case the machine is stopped for any reason during the middle of a reel and then started up again. — Altec Eng. Dept. Bulb Rectifier Relay Failures In May, 1946, I installed a pair of bulb-type rectifiers, using six 15-ampere Tungars. It was for 220-volt, 3-phase, 60-cycle supply. After ten months I had an emergency call because two opposite tubes did not light. This was due to burned contacts on the relay (General Electric A. C. Contactor Type CR28101820 B2). To get at this relay requires (Continued on page 35) 26 INTERNATIONAL PROJECTIONIST • November 1^947