Canon LBP-1120 Service Manual

Also see for Laser Shot LBP-1120: Specifications User guide Getting started guide

Contents

CHAPTER 22 - 8B. Fixing Control Circuit1. Fixing Temperature ControlThe fixing film unit of the printer contains a plate-shaped fixing heater to heat up the fixing film.The fixing heater temperature is detected by the thermistor (TH701) on the fixing heater. When the temperaturerises, the resistance of TH701 drops and the voltage of the FIXING HEATER TEMPERATURE DETECTION signal(FSRTH) decreases.The CPU (IC201) on the engine controller PCB outputs the FIXING HEATER DRIVE signal (FSRD) based on theFSRTH signal voltage to bring the fixing heater temperature to the specified value.The fixing heater temperature is controlled by the following three modes:1) Initial temperature control: Increases to the normal target temperature after the pickup command is input to theengine controller.2) Normal temperature control: Maintains the normal target temperature (about 190°C) during printing.3) Between-page temperature control: Controls at low temperature in order to prevent the temperature rise at the non-feeding areas between pages on the fixing film.Figure 2-2-42. Fixing Heater Safety CircuitThis circuit is installed on the engine controller PCB and always monitors the abnormal rise of the fixing temperature.When the output voltage from the thermistor falls below about 0.67V (244°C) due to the elevation of the fixingheater temperature, the output of the comparator (IC302) becomes “L” and the relay (RL101) goes OFF, cutting offpower to the fixing heater.Fixing heater(H701)IC201FSRTHCPU27FSRD38 Pressure roller(TH701)ThermistorFixing film unitJ102-2J102-1+3.3V+3.3V+24VINL101FU101IC302SSR101/RLYDEngine controller PCBThermal fuse(FU701)35+3.3V+3.3VRL101+24VJ206-1J206-2Fixing heater safety circuit