JVC 330 Service Manual

Contents

Chapter 2—Functional DescriptionModel 330, 340SC and 370SC Service Manual 2-75PrismThe prism receives the high intensity light from the xenon arc lamp and polarizesthe light horizontally. The prism reflects virtually all of this light toward the ILA®assembly. This light is then phase modulated into a vertical plane by the input sideof the ILA® assembly and then reflected back toward the same prism. Since theprism reflects only horizontal light and passes vertical light, this high intensity,vertically polarized image goes straight through the prism and into the projectionlens.Projection LensThe projection lens picks up the high intensity image from the prism and transmitsit to the projector screen. The projection lenses are individually mounted so theycan be focused and aligned separately. The green lens is fixed horizontally and thered and blue lenses allow horizontal movement to align them with the green lens.Various focal lengths, (focal length = throw distance/screen width), are availablefor different sized rooms and screens.Arc Lamp AssemblyThe high intensity light from the Xenon Arc Lamp produces a “full screen” outputof between 3,000 and 6,800 lumens, depending on the model of projector. Theoutput from the arc lamp, along with the output from the ILA® Assemblies,produces the images on the screen.NOTE: To protect equipment and personnel against explosion hazard, the arclamp is covered with a safety glass plate and is mounted in a protective metalhousing. This housing provides protection and ensures accurate alignment of thearc lamp optical axis with the projector housing by means of machined surfacesand precision alignment pins.The Arc Lamp itself, a gas-filled device, maintains a relatively constant voltage.It, therefore becomes the voltage controlled device and the SPS Arc Lamp supplycontrols the current to the lamp. The constant voltage maintained by the lamp andthe constant current provided by the SPS result in a constant power supplied to theArc Lamp.The arc lamp and reflector housing is never disassembled in the field. The arclamp is replaced by exchanging the complete assembly.The Arc Lamp Assembly also includes the Ignitor and its circuitry. The Ignitorcircuit provides a momentary high voltage that excites the xenon gas inside theArc Lamp. After the arc lamp is struck and turns on, it is maintained by a high-current, low-voltage power supply.