II. FIXING CONTROL CIRCUITA. Controlling the Fixing TemperatureFigure 6-201The fixing temperature is monitored by the upper thermistor (THU) mounted on theupper fixing roller and the lower thermistor (THL) mounted on the lower fixing roller.When the surface temperature of the upper fixing roller and the lower fixing rollerincreases, the resistance of THU and THL will decrease, gradually lowering the voltageof the fixing temperature detection signal (FXTHU, FXTHL) sent to the M-CPU (IC202)on the DC controller PCB.The M-CPU on the DC controller PCB controls the fixing heater drive signal (FXUON,FXLON) according to the voltage of the FXTHU and FXTHL signals and through theexpansion I/O (IC203) so that the fixing temperature remains a specific value.COPYRIGHT © 1999 CANON INC. CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)CHAPTER 6 FIXING SYSTEM6-2Power supply assembly DC controller PCBFixing assemblyFXUONFXLONUpper thermalswitchUpperfixing rollerLowerfixing rollerFixing heaterdrive circuitRL101IC203ExpansionI/OIC202M-CPUBUS(THU)Upper thermistor(THL)Lower thermistorLowerthermal switchFXUONSFXLONS313021222324FXTHUFXTHL+5V+5V+5V+5VSub driver circuitSub drive circuitDownload free service manual at http://printer1.blogspot.com
