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MANAGERS AND PROJECTIONISTS 793
The claim of the manufacturer is that the control is such that both the positive crater and the tip of the negative carbon will be kept within 1/32 of an inch of their fixed position for an entire trim of carbons, without any attention on the part of the projectionist, and with no possibility of the positive crater working slowly out of position.
HAND FEED.— Both the rotating shaft and both carbon feeds have auxiliary hand feed controls, so that the lamp may at any time be operated by hand. By moving small slide bar 5-125, Fig. 304 to the left, both automatic carbon feeds will be cut out by stops on the slide bar which hold the feed pawls out of engagement with their ratchets.
CAUTION. — After striking the arc, and before you do anything else, be sure the slide bar is pushed to the right, and that the automatic feeds are functioning properly. If the automatic feeds are cut out and the projectionist does not feed the lamp by hand, damage may and probably will be done to the tip of the third electrode by the burning of the positive crater back under it.
The automatic control unit is attached to the lamphouse by means of three screws, one of which is in stud 5-128, Fig. 305, and the other two in the holes in the cross plate just above the motor, Fig. 305.
Cover 5-102, Fig. 304, attaches by means of four screws. The three springs beside the cover slip over the ratchet hubs, hold them in their bearings and supply enough friction that the ratchet will not be dragged backward by the receding pawls.
In replacing cover plate 5-102, Fig. 304, be careful that the three< springs are in their proper places, that slide-bar 5-125 is seated in its groove and that none of the parts bind, due to pressure of the cover plate. The freeness of the pawls may be tested by pressing the finger on the magnet armatures, noticing whether or not they move easily and travel their normal distance, or until the armature is stopped by the adjusting screw.
The following spare parts should be carried for the Automatic control units : (See page 869.)
Two sets motor brushes.
Two negative feed magnet springs, 5-149.
Two spring coupling, 5-105.