B. Controlling the Scanning Lamp Intensity1. OutlineFigure 4-105 shows the circuit used to control the intensity of the scanning lamp, andthe circuit has the following functions:q Turning ON and OFF the scanning lamp.w Controlling the intensity of the scanning lamp.• Maintains the intensity to a specific level against changes in the voltage of thepower supply.• Controls the intensity to suit the sensitivity of the drum.• Controls the intensity to suit the density of the originals (AE control).e Checks the activation of the scanning lamp.2. Operationsa. Turning ON and OFF the Scanning LampWhen LAON (scanning lamp ON signal) is ‘0’, the output of the differentialamplification/potential control circuit goes ‘0’, keeping the arc circuit from turning ONand, thereby, not supplying power to the scanning lamp (LA1).When LAON goes ‘1’, the output of the differential amplifier/phase control circuitgoes ‘1’, causing the arc circuit to turn ON and, thereby, supplying power to the scanninglamp (LA1).b. Controlling the Intensity of the Scanning LampThe intensity of the scanning lamp is increased or decreased by controlling thesupply voltage to the scanning lamp according to the intensity adjustment signal (LINT)from the DC controller PCB.Figure 4-105Q156D/AconverterQ159Errordetectioncircuit12VPWOFFJ111-B6J111-B7J111-B8CVRONLINTLAONJ503-4J503-2J503-2Lamp ONdetectioncircuitPower switchSW1ScanninglampJ501-1Arc circuitLamp regulatorDC controller PCBHIM1Differentialamplifierphase controlpower voltagecircuitJ501-3Microprocessor(master)ThermalfuseTP2COPYRIGHT © 1997 CANON INC. CANON NP6045 REV. 1 MAR. 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)CHAPTER 4 IMAGE FORMATION SYSTEM4-6
