Chapter 22-361. Sets the FIXING HEATER DRIVE (FSRD) signal "L" through the ASIC and shuts off the heater.2. Sets the RELAY DRIVE (RLD) signal "L" through the ASIC.3. Sets the RELAY DRIVE (RLD-) signal "L" through the fixing heater safety circuit.4. Turns off the relay (RL301) through the relay drive circuit and shuts off the heater.2) Protective function by the fixing heater safety circuitThis circuit monitors the output voltages (FSRTH1, FSRTH2) of the main/sub thermistors.When the FSRTH1 is approx. 0.5 V or less (equivalent to 280 deg C or higher), or the FSRTH2 is approx 3.0 V or higher (equivalent to 315 deg C or higher), therelay (RL301) is turned off and the heater is shut off.3) Protective function by the thermoswitchThe thermoswitch (TP) gets disconnected to interrupt the current to the fixing heater when itreads the temperature of over 250 deg C (Note) due to an abnormal temperature rise of the fixingheater.The thermoswitch is placed away from the fixing heater. The actual temperature of the fixing heater is higher than the thermoswitch reading.2.5.3.3 Fixing Unit Failure Detection 0011-6413The CPU determines fixing unit failures under the following conditions 1) - 3), turns off the relay (RL301), shuts off the heater, simultaneously notifies the failureto the SCNT board:1) Abnormal high temperature* Abnormal high temperature on the main thermistorIf the main thermistor continuously reads 245 deg C or higher for minimum 1 second, the CPU judgesit abnormally high.* Abnormal high temperature on the sub thermistorIf the sub thermistor continuously reads 290 deg C or higher for minimum 1.5 seconds, the CPU judges it abnormally high.2) Abnormal low temperature* Low temperature during temperature controlIf the main thermistor continuously detects below 100 deg C for minimum 1 second during the printtemperature control and between-sheets temperature control, the CPU judges it abnormal.* Abnormal low temperature on the sub thermistorIf the sub thermistor continuously reads below 75 deg C for minimum 2 seconds after 20 seconds from when the heater is energized, the CPU judges it abnormal.* Break during start-up in the sub thermistorIf the sub thermistor continuously reads below 40 deg C for minimum 1 second after the heater isenergized, the CPU judges that the sub thermistor has a break.* Break in the main thermistorIf the main thermistor continuously reads below 40 deg C for minimum 0.5 second after the start-uptemperature control, the CPU judges that the main thermistor has a break.* Break in the sub thermistorIf the sub thermistor continuously reads below 40 deg C for minimum 0.5 second after the start-uptemperature control, the CPU judges that the sub thermistor has a break.3) Start-up abnormality* Start-up abnormality 1If the main thermistor continuously reads below 120 deg C for minimum 1 second after 20 secondsfrom when the heater is energized, the CPU judges it abnormal.* Start-up abnormality 2If the main thermistor reading never exceeds 5 deg C below the target temperature of temperaturecontrol within 75 seconds from when the heater is energized, the CPU judges it abnormal.2.6 Engine Control System2.6.1 Construction2.6.1.1 Overview 0008-1724The printer control system controls the laser exposure system, image formation system, pickup/feed system, delivery system, fixing system, and control system.The printer control system consists of 2 boards: DCNT board and SCNT board.The following is a block diagram of the printer control system; a brief description of individual circuits follow:F-2-51Printer control systemDCNTboardSCNTboardLaser exposure systemImage formation systemPickup/feed, delivery systemFixing systemExternals and controls systemPrint Control System Block Diagram
