HP LaserJet 5000 Service Manual - Page 102

The Scanner Motor is controlled and monitored by the DC Controller Board. It rotates the scanner mirror during the Initial Rotation period and the print period. The fan motor is a two-phase, four-pole DC brushless motor containing a hall element and forms a unit along with the motor drive circuit. When the printer turns on, the CPU (IC301) on the DC controller PCA makes pin 99 (/HALFFAN) "H" and runs the fan motor half a turn. The CPU controls the half-speed/full-speed rotations according to the target fixing roller temperature when the CPU receives the /PRNT signal from the video controller PCA. When the fixing unit warms up sufficiently, it makes pin 99 (/HALFFAN) "H" to set the fan drive voltage (FANON) to the voltage level to run the fan motor at full speed. If the printing ends, the fan motor is run at full speed for 30 seconds after the main motor stops, then the fan motor runs at half speed. EN Power Supply System 5-11