C. Controlling the Supply Power for the Fixing HeaterThe temperature of the fixing heater is controlled by controlling the power suppliedto the fixing heater.The resistance of the plane-shaped heater used as the fixing heater may show somevariation depending on which production lot it comes from.For this reason, whenever you have replaced the copier’s heater, you must store theresistance value in service mode (No. 304; see p. 10-31); this way, the microprocessoron the DC controller PCB can exert proper control over power.Caution:The resistance of the fixing heater is stored in service mode at the time the copieris shipped out of the factory; do not change it unless you have replaced the fixingheater.The power of the fixing heater is controlled by a phase power control method.The microprocessor controls the output timing of the fixing heater drive signal(HTRD) so that power that suits the target temperature of the fixing heater may besupplied to the heater (potential control of the supply power).Figure 6-104COPYRIGHT © 1997 CANON INC. CANON NP6218 REV. 0 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)CHAPTER 6 FIXING SYSTEM6-5HTRDSupply powerto heater
