Engine control subsystems Laser/scanner control Based on information received from the engine controller PCB, the formatter sends a direct signal to modulate the laser diode on and off. The modulated laser beam strikes the surface of a rotating scanning mirror, then a focusing lens directs the beam onto the photosensitive drum. The printing system synchronizes the process by continuously monitoring the beam detect signal. Paper-feed control The engine controller PCB controls paper motion by continuously monitoring the various paper- sensor levers, and coordinating the timing with the other print processes and systems. See “Pickup/ feed system” on page 86.
Microswitch control The engine controller PCB controls the following microswitches and reports any errors to the formatter: Top door and toner cartridge switch. Activated if the top door is open. The toner cartridge is detected electronically. Engine test switch. Activated manually through an access hole on the side of the gear plate. This switch causes the print engine to perform a self-test diagnostic, bypassing the formatter. See "Engine test" in chapter 7. Motor control The engine controller PCB controls the following motors and reports any failures to the formatter. See “Basic print-period operating sequences” on page 71. Main motor.
Rotates during interim period (following initial power on), print, and last rotation, or when the top cover is opened or closed. Scanner motor. Operates during the interim period and the print period. Fan motor. Rotates at full speed while the main motor is rotating and continues rotating for 30 seconds after the main motor stops. Rotates at full speed, half speed, and then stops during power-on and the standby period. Reverse motor. A stepping motor responsible for changing the paper direction. It is capable of clockwise and counterclockwise rotation. Fuser-assembly control The fuser assembly’s film contains a heater.
The engine controller PCB controls the fuser heater during the following temperature modes. See “Basic print-period operating sequences” on page 71. initial print between-page postprint The engine controller PCB maintains the fuser at a temperature of 195 degrees C (383 degrees F) during print temperature mode. If the fuser system overheats, reaching about 220 degrees C (428 degrees F), a relay opens the power circuit to the fuser heater, causing a fuser error message. If the fuser system exceeds 230 degrees C (446 degrees F), the thermal fuse melts, cutting off power to the fuser assembly. The engine controller PCB monitors the fuser heater temperature through a thermistor.
78 Chapter 5 Theory of operation C7058-90936