80 Chapter 5 Functional Overview C4170-90959
NOTE: The Intermediate PCB is only a connection point to the Engine Controller Assembly. Before
replacing the Engine Controller Assembly, make sure that the Intermediate PCB is not
damaged and that the connections are correct.
Laser Scanner Control
Based on information received from the Engine Controller Assembly, the formatter sends a
signal directly 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 Assembly controls paper motion by continuously monitoring the
various paper sensor levers, and coordinating the timing with the other print processes and
systems. See “Paper Pick and Feed System” (page 89) for more information.
Microswitch Control
The Engine Controller Assembly controls the following microswitches and reports any errors
to the Formatter:
• Top door and toner cartridge (SW1701). Activated if the top door is open. The toner
cartridge is detected electronically.
• Engine test (SW701). Activated manually through an access hole on the rear of the
printer. This switch causes the print engine to perform a self test diagnostic, bypassing
the formatter. See “Engine Test” (page 108).
Motor Control
The Engine Controller Assembly controls the following motors and reports any failures to the
formatter. See “Sequence of Operation” (page 70) for more information on timing periods.
• 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.
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