Canon NP1550 Service Manual

Also see for NP1550: Service manual

I OPERATIONS AND TIMING!B. Fixing and Paper DeliveryAssemblies1. OutlineThe upper and lower rollers of the fixingassembly are driven by the main motor (M1).The upper roller is heated by a singleheater (H1:900W). When the surfacetemperature of the roller rises, the resistanceof the thermistor (TH) falls, so the voltage ofthe signal that it produces FIXING ROLLERSURFACE TEMPERATURE signal (TH1)also falls.Whether the voltage of TH1 (analog) isabove or below a certain level at a given timedetermines if the microprocessor of the DCcontroller makes the HEATER DRIVE com-mand (HTRD) "1" or "0".The NP-1550 is provided with thefollowing three protection mechanisms:• The microprocessor monitors thevoltage of TH1 and indicates 'E000' o r 'E001'in response to an error, i.e., ACOFF goes '0'to turn the relay (S105) OFF, thereby cuttingthe power to the fixing heater.• The fixing roller error detection circuitmonitors the voltage of TH1 and, when itdrops below 0.9V (equivalent of 215°C),turns HTRD OFF.• The thermo switch (TS1) goes OFFwhen the temperature of its inside rises to230°C to cut off the power to the fixingheater.'Trie thermo switch (TS1) cannot beused after its contact has opened; thei<;e^ht^:yplhnc>fi'y^at room temperature.Fixing roller heater H1900WUpper fixing rollerJ317: 2Delivery rollersLower fixing rollerThermo-switchTS1 (F1 ) 230°C©iThermistor (TH)\lS105 •y?r lV/T JZ.J306-2. 24VHTRD |J304-4I5V! CWT) 24VL__ IAC driver PCB J306-4iACOFF L_ rDC controller PCBFigure 3-39COPYRIGHT© 1992 CANON INC. CANON NP-1550 REV.1 SEPT. 1992 PRINTED IN JAPAN (IHPRIME AU JAPON] 3-35