Canon NP1550 Service Manual

Also see for NP1550: Service manual

OPERATIONS AND TIMING IC. Controlling the ScanningLamp1. OutlineThe scanning lamp (LA1) is controlled bythe DC controller PCB; see Figure 3-18.Specifically, the DC controller• turns the scanning lamp ON and OFF.• controls the intensity of the scanninglamp.2. Mechanisma. Turning the Scanning Lamp ON and OFFThe microprocessor (Q303) on the DCcontroller PCB controls the lamp regula-tor. The scanning lamp goes ON whenthe scanning LAMP ON command (LAON)is '1', and it goes OFF when the signal is'0'.b. Controlling the Intensity of the ScanningLampThe intensity of the scanning lamp isswitched between when the black devel-oping assembly is used and when the CTunit is used.When the CT unit is used, the LIGHTINTENSITY CONTROL command (LIC)goes '0' to raise the lamp voltage byabout 3.5 V higher than when the blackdeveloping assembly is used.During AE exposure, however, thevoltage (70 V) applied to the scanninglamp remains the same.The NP-1550 adjusts the copy densityusing its development bias; see p. 3-22.Error ProtectionThe> condition of the scanning lamp ismonitored using the LIGHT signal(LGHT).If the LIGHT signal (LIGHT) is receivedby the DC controller for about 20 sec, theerror detection circ uit generates the ACSHUTOFF signal (ACOFF) to force therelay (S105) on the AC driver/DC powersupply, PCB to go OFF, thereby cuttingAC power supply (P. 3-39). In this caseE220 error is displayed.DC controller PCB Lamp regulatorFigure 3-183-20 COPYRIGHT© 1992 CANON INC. CANON NP-1550 REV.1 SEPT. 1992 PRINTED IN JAPAN (IMPRIKE AU JAP0N)