Canon PC980 Service Manual - Page 56

CHAPTER 3 EXPOSURE SYSTEM 4. Controlling the Copying Speed The machine uses a halogen lamp for scanning, and the heat of the lamp increases the tempera- ture of the copyboard. To prevent possible overheating of the copyboard glass, the temperature of the scanner is monitored by a thermistor (TH2); if its reading reaches 37.5°C or higher, the copying speed is reduced to 6 cpm. If this mechanism turns on during continuous copying, it remains on until the end of the copying job. At the end of copying, if the reading of the thermistor is 34.5°C or higher, the No. 1 mirror mount is moved forward 105 mm from the home position and stopped, thereby lowering the temperature of the copyboard fast. Reference: While the copying speed is controlled to 6 cpm, the speed of the reverse movement of the scanner is reduced to prevent overheating of the copyboard glass. (about 75 mm/sec) Switching to 6-cpm copying speed SCRV SCFW SCRV SCFW SCRV SCFW SCRV LSTR STBY

,
,, Check timing by thermistor (TH2) Main motor (M1) Pickup clutch solenoid (SL1) Registration clutch solenoid (SL2) Scanner 37.5˚C or higher I 34.5˚C or higher II I : When the pre-registration roller paper sensor (Q751) is off, the pickup clutch solenoid is turned off to prevent overheating of the pickup clutch solenoid (SL1). II : By the time the Copy Start key is pressed or the power switch is turned off and then on again next time, the scanner is moved to and stopped at 105 mm forward from the home position. Figure 3-106 3-6 COPYRIGHT © 1999 CANON INC. CANON PC800s/900s REV.0 AUG. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)