2. Operationa. Turning On and Off the Scanning LampWhen LAON (scanning lamp activation signal) is ‘0’, the output of the differentialamplification/phase control circuit goes ‘0’, and the arc circuit remains off, depriving thescanning lamp (LA1) of power.When LAON is ‘1’, on the other hand, the output of the differentialamplification/phase control circuit goes ‘1’, and the arc circuit turns on, supplying thescanning lamp (LA1) with power.b. Controlling the Intensity of the Scanning LampThe intensity of the scanning lamp is controlled by controlling the voltage of powersupplied to the scanning lamp according to the intensity adjustment signal (LINT) fromthe DC controller PCB.LINT varies the pulse duty between 10% and 57.6% according to the setting of theCopy Density key or the density of the original, sensitivity of the drum, and setting of theintensity control VR so that the effective value of the voltage of power to the scanninglamp will vary between 45 and 65 V (phase control).Figure 4-106c. Checking the Activation of the Scanning LampWhile the scanning lamp remains on, the activation detection circuit generates theactivation detection signal (CVRON) at all times. CVRON is sent to the error detectioncircuit on the DC controller PCB.If the lamp activation signal (LAON) goes ‘0’ and the scanning lamp turns onbecause of a short in the activation circuit or the like, the DC controller PCB causesPWOFF to go ‘0’, thereby turning off the relay inside the power switch and, ultimately,turning off the power switch (SW1); this condition deprives the lamp regulator of ACpower.3. Auto Exposure ControlThe machine is equipped with an auto exposure mechanism which automaticallycontrols the intensity of the scanning lamp to suit the density of the originals.When copies are made in auto exposure (AE) mode, you can obtain fogging-freecopies without having to adjust the copy density manually. The intensity of the lampcontrolled by the AE mechanism is indicated on the control panel.AE mode may be executed on the copier side or the RDF side, the latter of which isused when originals are placed in the RDF. The copier’s AE mode is used, however,when manual feeding is selected.Pulse duty: 10%Pulse duty: 50%COPYRIGHT © 1997 CANON INC. CANON NP6350/NP6251 REV. 0 JULY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)CHAPTER 4 IMAGE FORMATION SYSTEM4-7Download service manual and resetter printer at http://printer1.blogspot.com
