3M 2100 Service Manual

Also see for 2100: Illustrated parts breakdown

Contents

3M 2100 Service Manual Manual pdf 6 page image

9/921-3MODEL 2100 OVERHEAD PROJECTORPRINCIPLES OF OPERATIONOptics (See Figure 1-2)The light source for the Overhead Projectoris 275 watt, 24 volt, Tungsten Lamp listedas ANSI Code FNT and rated at 75 hours.An external reflector is needed with thislamp.Care should be exercised to preventexcessive vibration or jarring of theprojector when the lamp is on. The lampfilament becomes more brittle at theoperating temperature of the projector andshocks may cause premature failure of thelamp.The glass envelope should not be touchedby the fingers when inserting the lamp inthe lampholder. Oils on the skin maycombine with the glass to form blisterswhich also will shorten the life of the lamp.The Fresnel lens, located above the lampand directly beneath the projection stage, isa condensing lens which consists of aseries of concentric rings, each of whichhas a surface curvature similar to that of athick smooth lens. The Fresnel lens is madeof plastic and may be severely damaged ifthe fan is stopped or the paths of cooling airblocked. Proper alignment and direction ofthe Fresnel lens is essential in order tomaintain the resolution and brightnessspecifications for the projector.The stage glass provides a convenient flatsurface for placing transparencies and othermaterials to be projected. Because the lightpasses through the stage, these projectionmaterials must be transparent.There are two (2) different projection headassemblies available for the projector. Oneis an Open Triplet Head with focuscorrection which has a triplet lens and frontsurface mirror and the second a closedDoublet Head which has one or twocondensing lens(es) and a front surfacemirror. The projection head is locateddirectly over the center of the Fresnel Lens.The projector is focused by raising orlowering the projection head.Proper alignment of the optical componentsand a clean machine are essential if themaximum operating capabilities of theoverhead projector are to be realized.Cleaning and alignment procedures arediscussed in Sections 2 and 4 inclusive.Cooling (See Figure 1-3)Cooling of the overhead projector isaccomplished by a motor-driven fan locatednext to the lamp housing. The cooling airenters the projector through opening “A”and exits through opening “B.” (See Figure1-3) It’s important that the flow of cooling airnot be restricted either by placing projectortoo close to a wall (about one footclearance is necessary) or by leavingforeign objects inside the projector.