International projectionist (Jan 1943-Dec 1944)

This department is a collection of random thoughts and some not so random; fact, 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 ol the serviceman's activities are invited. Emergency Operation of TA-4144 Power Units In case of failure of the exciter supply TA-7351, the TA-4144 Power Unit will furnish exciter lamp current. In many installations, a wire has been pulled from the TA-4144 Power Unit to the TA-7351 Power Unit for this purpose. A note was left in the units outlining the procedure for emergency operation. It is also suggested that a small note be posted on the outside of the unit, being a constant reminder of the emergency hookup available. — A. E. Nolan, RCA. Removing Foreign Matter From Film Here is an easy way to remove any foreign matter such as hair, lint, or dirt, which might get into the aperture of the projector while the machine is running. Use a little oil or clean grease on the emulsion side of the film applied on the upper intermittent loop. As the film travels down past the aperture all foreign matter will adhere on the spot where the oil is applied. Mark the spot well on the reel below so that the film can be cleaned upon rewinding. I have tried this method under some very stubborn conditions and have found it very successful without the necessity of stopping the show. — Nat Ripp, RCA. Checking Relay Contacts Relay contacts occasionally continue to arc even after careful cleaning. This can be detected by holding a small mirror under the relay and darkening the projection room. If the relay is still arcing, it will be plainly visible in the mirror. — Hall Prosser, RCA. Conservation of Stop Pins In the MI-9701 Fader Switch, one of the three stop pins receives more wear than the others because in normal operation it is continually swung back and forth from No. 1 to No. 2 position. When this pin begins to show wear, it is advisable to transfer operation to one of the other two pins. This can easily be done by changing the inputs to the switch as follows: At the terminal board connect the external input wires from machines No. 1 to No. 3 on the board; connect machine No. 2 to No. 1 on the board, and connect special input No. 3 to No. 2 on the board. These wires should be plainly tagged so that when checking the switch connections one will know exactly what change has been made. The knob should then be given a one-third turn so that the proper machine is indicated. This procedure will greatly increase the life of the stop pins. Frequent cleaning and lubrication of these pins will reduce the wear considerably. — R. 0. Northrop, RCA. Matching a High Impedance Output to Amplifier A PEC transformer makes a good matching transformer on any equipment having a low impedance input for matching high impedance microphone or phonograph pickup. — A. C. Holland. RCA. Simplifying Removal of Fuses By winding a piece of friction tape about %" wide by IV2" long around the small 1, 2, or 3 ampere glass fuses, they can be removed or replaced very easily without danger of getting a shock. This same procedure may be followed to facilitate the removal of any type fuse. — G. E. Reiger. RCA. Improving Operation of Victory Carbons Since these carbons have a higher resistance than the old ones, there is considerably more variation between a full trim and a stub than there was on the old carbons. For this reason, some projectionists leave only enough carbon projecting from the jaws to run the reel in the machine rather than clamp a new carbon near the end. In this way, the resistance is lower and there is less trouble with erratic speed. The projectionist has to reset the carbons for every reel but the arcs burn more steadily. — B. D. Douglas. RCA. Precaution Against Shorting Power Unit Transformer As a precaution against shorting plate and filament when installing or removing a No. 29225 Rectifier from the socket in an MI-9520 Power Unit, a calling card may be placed between the plate contact and the tube base. The card may be extended down between the shell of the socket and the porcelain, thus giving good protection when changing lubes while the transformer is being used for emergency a.c. exciter lamp operation. — Carl Welsher, RCA. Reconditioning Equipment Damaged by Fire In covering a fire job recently where one of the projectors and soundheads were badly damaged by fire, considerable experimenting was done in an effort to find a satisfactory solvent that would remove the burned film and smoke from metal and glass projector and soundhead parts easily and without damage. It was found that acetone, obtainable at all drug stores, cleans the glass parts quickly and with very little effort, while the metal parts may be cleaned with peroxide. (Acetone has very little effect on metal.) The parts should then be wiped thoroughly dry and oiled to prevent rust or corrosion. — C. R. Shepard, RCA. Emergency Exciter Lamp Operation Since the physical characteristics of a 27-volt, 1-ampere exciter lamp is the same as a 10-volt or 7%-volt lamp, a 27-volt exciter lamp can be used in emergency to replace either of the two lamps if a rectifier supplying 27 volts to an arc lamp is available. There are many of these rectifier sources available and it is an excellent idea to carry a 27volt lamp as an emergency spare. If the arc lamp supply is a generator, the voltage is in the vicinity of 45 volts. A low-voltage bulb, the type used in batterylighting emergency systems, will give the correct voltage drop when connected in series with the 27-volt exciter and arc supply. A suitable resistor may also be connected in series with the 27-volt lamp to provide emergency operation. — Anthony W. Falcone, RCA. Conservation of Replacement Pxrts When the stop plate for the pressure roller assembly of the PS-24 soundhead wears so that a notch forms at the retaining pin and the pressure roller is not held sufficiently close to the drum, drill two holes at the opposite end and turn the plate. This method eliminates replacement of the entire stop plate. — W. Wall, RCA. (Continued on page 20) APRIL 1943 13