International projectionist (Jan-Dec 1935)

Trouble Charts Enable Quick Equipment Repairs By A. C. SCHROEDER MEMBER, I. A. PROJECTIONIST LOCAL ISO, LOS ANGELES, CALIF. PREPAREDNESS in the projection room very often is not thought of until old man trouble sneaks up on us and raises the devil. Something goes wrong, and then we find that our memory has gone back on us. Which fuse is the one for the exciter lamp circuit? which contactor is the one for the Number 2 machine? or in what part of the circuit is the attenuator? When checking circuits and apparatus we say to ourself that we know just where everything is ; but did you ever put something away and then a few days later be unable to remember where it was? The answer to all this uncertainty is a set of charts, covering everything in the projection room, and some things outside, but closely associated with it, such as grids for the arcs, batteries for the amplifiers, motor generators for the amplifiers and for the arcs, etc. Some of these charts accompany this article. Yours will not be exactly like these, but they will be similar. If you should make up a set to fit your room, do not say, "I'll remember this, so there is no need of putting that down here." You probably will not remember it when the hour of need arises. They are alright if you are sure that you will know what they stand for a year, or even three months, from now. Even when there is no trouble, but changes in the wiring or the equipment are contemplated, a set of drawings will often pay for themselves in the time saved in planning the work. It will not be necessary to chase everything out to "see where this goes" and "where that goes." A glance at one or more drawings will show these things at once, and often will bring things to mind that save time and money by having all needed material on the job before starting, or at least ordered and on the way so it will be handy when ready for it. Material Shortage Imagine planning and starting a job and then being without some needed material. The next day (sure, most of our changes are made between 12 midnight and 8 or 9 a. m.), the needed stuff is ordered, but we are informed that it is not obtainable in town and must be ordered from some other city! Well, if you are a cussin' man, this is the time to demonstrate such talent. In Figure 1 we have the general wiring of the projection room: lights, machine motors, dowsers, etc. You can make your drawings with more detail or you can leave some of it out. For instance, the wiring in the fuse panel can be shown, or it can be drawn in outline only, as in this figure. On the other hand, the three wires for each dowser can be shown just by one line, to show what parts are connected, since we know that it takes three wires to operate it. The panel in your room may not have all the circuits as shown here. The battery charger, 42 amplifier, and M. G. set for the horn field supply may be fused outside the room, or there may be another panel in the room to take care of some of the circuits. Then, again, your panel may have all these and many more. There may be three machines, curtain controls, and even house lights. If your outfit has a motor control cabinet, show that, and don't forget that there are fuses and a switch in the box. REGULAR AND EMERGENCy 3-PHASE SUPPLY FIGURE 2 GRIDS SWITCHES -STARTER FIELD RHEOSTAT M.G SWITCH BOARD ./Hr PROJ. ^2-i PROJ. STEREO .STEREO SPOT 42 AMP. HORN M.& BAT CHARGER fuse: PANEL STA.#I. Q-Tj DOWSER MOTOR MACH. LIGHTS BOOTH LIGHTS FRAMING LIGHTS U n_r STA *Z. DOWSER MOTOR FIGURE 1 Some installations have the switch cut out, some may have the fuses cut out, although I have never seen that. Some have a door switch on the box. Make a note of these things or show them in the drawing. Whatever circuits and equipment you may have and however it is arranged, make your drawings neat and accurate. Notes and lettering should be legible and give all information that may be required. You need not be a draughtsman to make neat and understandable drawings. Projector Arc Circuits In Figure 2 we have the arc circuits and their supply. Here again there may be many variations. Possibly you have no emergency supply, or you may have a gas engine for this purpose. Where I work we have the regular set running on 220 volts, while for emergency and for stage shows we use an enormous generator (that is, enormous for a picture theatre) the motor of which runs directly off the 2300-volt supply. The other end of the generator is coupled to a large Winton stationary engine through a dog clutch. Anything of this sort in your theatre could be in the drawing. Maybe you use a mercury-arc rectifier, or one of the new copper-oxide rectifiers. Some houses use DC right off the lines. I have even heard of one house that used 500 volts DC, breaking it down by the [19]