- Hewlett-Packard Printers Service Manual

Engine Controller System 5-13
Motors
See “Timing Diagram” on page 5-50 for specific timing details for the
printer motors.
The Main Motor, MT1, is controlled by the Engine Controller Board.
The Main Motor drives the Main Gear Assembly and rotates during
the initial rotation period (following power-on), the print period, the last
rotation period, or whenever the printer’s Top Cover is opened and
closed.
Figure 5-8 Main Motor Control
The Main Motor is a DC brushless motor and is unified with the motor
drive circuit.
The CPU (IC501) sets the Main Motor Drive signal (/MON) to “L” and
rotates the Main Motor. When the HP LaserJet 4000 series printer is
printing at 1200 dpi, the CPU sets the main motor rotation switching
signal (/HALF) to “L” and decreases the rotation speed of the Main
Motor to half. The HP LaserJet 4050 prints 1200 dpi at engine speed.