International projectionist (Jan-Dec 1946)

AT YOUR SERVICE **.*"> ..;., **>n ■ This department is a collection of random thoughts and some not so random: iact. fancy and opinion relating to the man behind the man behind the gun — the serviceman. The prime purpose of this section is to promote a closer relationship between serviceman and projectionist based on a better understanding of their mutual problems through an exchange of news and views, kinks and kicks. To this end, contributions relative to any phase of the serviceman's activities are invited. Flexible Insulating Tubing A very good insulating "spaghetti" can be obtained from wartime solid house wire. A plastic insulation is used on this wire. Take a two or three-foot piece of $14 wire, strip one end slightly, place the bare wire in a vise and pull the insulation off. It can be removed easily without breaking. — R. H. Bisbie, RCA. Thrust Bearing for Film Magazines A ball thrust bearing placed on upper and lower magazine shafts next to frame will act as a clutch for smoother operation of film coming off these reels. Place the bearing on the shaft after the spring has been removed, replace the spring, and tighten nut for proper tension. — G. E. Reiger, RCA. Hint on Skinning "Mike" Cable For skinning microphone cable when making up connectors and making connections, the work can be made much easier if done with a pair of pointed scissors. — M. P. Demming, RCA. Card for Checking Optical Spot By notching an ordinary calling card, as shown in Fig. 1, the card may be inserted into the end of the rotary stabilizer for observing the spot from Notch Here Spot from Opt ical j System Rotary Stabilizer Drum (Cross Section View) Notch Here View) FIGURE 1 the soundhead optical system — without having to hold it in place by hand. — • Charles Graham. RCA. Volume Control Lubricant For years I have been trying to find something that would keep contacts and volume controls quiet. I believe my quest is ended, for I have been using a product for a year now and it has worked perfectly in every instance. For example, it will keep a W. E. fader quiet between alternate monthly calls, while previously the unit would hardly operate a week without needing attention. Also, the product has completely eliminated noise in the wire-wound controls, on some of which it has been 7 or 8 months for a single application. It has also worked well in controlling noise in the Yaxley controls such as are used for changeover and volume control mechanisms. The product is known as "No-Ox" and is made by the No-Ox Laboratories of Los Angeles and Chicago. — C. F. Craig, RCA. Marker for Reel Cabinets I have always used a China red pencil for marking film reel cabinets, to avoid errors in continuity, and it worked 0. K. I believe I have found something better, namely, "Stick-O-Paint," which is available in red, white or yellow from the Lake Chemical Co., 6 East Lake St., Chicago. This marker shows up very plainly, but it wipes off easily with a rag. Ask your local Police Dept. for a sample, as they use it for marking tires and windshields for overtime parking, etc. — Lester Van Buskirk, L. U. 744, Alpena, Mich. Checking Large Capacitors in Power Supply Units In power supply units a rapid check can be made on the capacitors by removing the capacitor fuses and turning the gain of the system up until the hum is quite prevalent. Replace the fuses one at a time and note the decrease in hum. If one capacitor seems inefficient, use a short jumper lead and cross it over to the choke connection on the opposite side, and by exchanging one capacitor with the other a comparison will result which will quickly locate the defective capacitor. Fuses may also be checked at the same time in the same manner. — C. R. Shepard, RCA. Emergency Battery Charger A 6-ampere Tungar rectifier bulb is connected in series with the battery to be charged, with a resistor also in series with the other elements. In Fig. 2, R is a 10-ohm, 200-watt resistor and can be Gampere Tungar Bulb To 110-Volt A.C. Line Resistance a) -vw t|l|l|l[ Storage Battery FIGURE 2 a heating appliance element. The ammeter is optional. For the circuit to function, one cell of the three-cell storage battery is connected to the Tungar filament: after it has been brought to normal temperature the switch to this "heating" circuit is opened and the circuit is connected to the 110-volt a. c. line as shown. The filament will continue to glow even though there is no heating current supplied. The rate of charge with the values shown is around 5 amps. — P. D. Colson, RCA. Tuning the 120-Cycle P. R. Filter Here is a simple way to check on the tuning of the 120-cycle parallel resonant filter used in small RCA sets to suppress a. c. exciter lamp hum: Open the external condenser connection and substitute a Cornell-Dubilier capacitor box (I have used the model CDB3. 01 to 1 mfd. in .01 steps to good advantage). When you arrive at the capacity for greatest attenuation, measured with an output meter and no film in the soundhead at maximum volume setting, replace with a capacity of the same value. — L. P. Work, Jam Handy JANUARY 194 6 23