HP LaserJet 6p/mp Service Manual - Page 58

Print engine control system Laser and scanner drive Based on information received from the Formatter, the DC Controller sends signals to the Laser/ Scanner Assembly to modulate the laser diode ON and OFF and to drive the Laser/Scanner motor. Refer to "Image formation system" later in this chapter for more information. Paper motion monitoring and control The DC Controller PCA controls paper motion by continuously monitoring the various paper sensors and coordinating the timing with the other print processes. For a detailed explanation of paper movement, and the interaction of photosensors and solenoid with the paper movement process, refer to "Paper feed system" later in this chapter. 12 V shutoff switch The 12 volt DC power shutoff switch, Switch 101, located on the top of the printer, is activated by the printer door. The front door must be closed before the printer can resume printing. Engine test switch The Test Print, Switch 201, located on the DC Controller, is activated manually through an access hole at the front of the printer. This switch causes the print engine to perform a self-test diagnostic which bypasses the Formatter PCA and prints a full page of black vertical lines. This test is useful for troubleshooting printer problems because it isolates the print engine from the Formatter PCA. (See Chapter 7, "Troubleshooting," to learn more about how to perform an engine test.) Motor The Motor is controlled by the DC Controller PCA. The Motor provides all of the printer's paper movement. Power system (on DC Controller PCA) The AC, DC, and high voltage power supply circuits are all contained within the DC Controller PCA. AC power distribution The AC power circuitry supplies AC voltage whenever the power cord is connected to the AC power source. AC voltage is distributed to the DC power supply circuitry and to the AC driver circuitry, which controls AC voltage to the fusing assembly's heating element. 56 Functional overview EN