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THE PROJECTOR 213
source used. Every morning the lamphouse floor should be cleaned of all refuse.
The frequency of examination of wires inside the lamphouse is dependent upon how heavily loaded they are, and what the normal temperature is inside the lamphouse. If the temperature is excessive, then, since the resistance of copper increases with increased temperature, the wires should be examined frequently. (22) If the wires are heavily loaded and the lamphouse temperature is high, the wires become more or less oxidized, and in this condition their resistance is very high and in danger of fusing at any moment.
(23) The condition of the stranded (asbestos covered) wires may be tested, roughly, by their resistance to bending. If they are stiff and hard to bend they are in fair condition; if they bend easily, then split the insulation and examine them. If they are dark brown clear through, replace them. Unless this is done, not only will power be wasted by their excessive resistance, but they will certainly fuse later and stop the show until replaced.
(24) If the wire shows dark brown on its outer surface, is stiff, and is copper-colored inside, it is still serviceable. Thf/ reference is to stranded asbestos covered wires only.
(25) At reasonable intervals — about once every two weeks — all wire connections (binding posts, etc.) should be taken apart and cleaned. Scrub the contact surfaces well with crocus cloth or 00 sandpaper. Very often a connection will form a thin, almost invisible scale of high resistence. This happens mostly in places of high temperature such as lamphouses, where it is good practice to clean all wire connections once a week.
Lamphouse Support and Alignment
(26) The rods upon which the lamphouse is mounted must have sufficient movement to enable the projectionist to locate the mirror or condenser at the proper distance from the aperture required by the optical system, (27)