Chapter 88-28.2 Various Control Mechanisms8.2.1 Controlling the Fixing Roller Temperature8.2.1.1 Controlling the Fixing Temperature 0006-2977The fixing film unit has a plate-shaped fixing heater built into it for heating the fixing film.The fixing heater is equipped with 2 thermistor: a main thermistor in the middle and a sub thermistor at the end. Themain thermistor is used to control the temperature of the fixing heater and to detect its overheating, while the subthermistor is used to detect an error temperature on the end of the fixing heater.The CPU on the DC controller PCB monitors the main thermistor signal (FSRTH) and the sub thermistor signal(SUBTH) from the thermistors for control of the fixing heater drive signal (FSRD0) and the relay drive signal(RLYD), thus varying the supply of power to the heater and, ultimately, controlling the temperature of the fixingheater.F-8-3The CPU on the DC controller PCB executes the following 4 types of fixing temperature control:- Start-Up Temperature ControlIn response to a print command from the image processor PCB, the temperature of the fixing heater is started up toa level 15 deg C/59 deg F lower than paper passage control temperature target.Fixing assemblyFixingheaterSubthermistorMainthermistorDC controller PCBPower supply PCBSUBTHFSRTH CPU+3.3VFSRDORLYD+24VImage processor PCBFixing heater high tempe-rature error detection
