HP LaserJet 4100 Service Manual - Page 440

Laser/scanner drive The HP LaserJet 4100 series printer has two diodes in the laser/scanner assembly. The printer uses a twin-beam method to scan two lines simultaneously. Based on information received from the formatter, the engine controller board sends signals to the laser scanner assembly to modulate the laser diodes on and off and to drive the laser scanner motor. See "Image formation system" on page 108 for more information. Paper-motion monitoring and control The engine controller board controls paper motion by continuously monitoring the various paper sensors and coordinating paper movement with the other print processes. For more information, see "Paper feed system" on page 117. Solenoids, sensors, clutches, and switches The engine controller board monitors the various sensors and switches in the printer and controls the solenoids and clutches for paper movement. See "Engine controller board inputs and outputs" on pages 96 through 100. Engine test print The engine controller board has a built-in engine test pattern that can be printed without using the data from the formatter. See "Engine test" on page 190 in chapter 7. Motors See "Timing diagram" on page 131 for specific timing details for the printer motors. This printer and optional input trays are driven by the main motor, which is controlled by commands from the CPU. EN Chapter 5 Theory of operation 101