Print engine control system

Printer laser/scanner drive

Based on information received from the formatter, the ECU sends signals to the laser/scanner assembly to modulate the laser diode “on” and “off” and to drive the laser/scanner motor. For more information, see “Image formation system” later in this chapter.

Paper motion monitoring and control

The ECU 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, see the “Printer feed system” section later in this chapter.

12-volt DC power shutoff switch

The 12-volt DC power shutoff switch (SW101), 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 engine test switch (SW201), located on the ECU, is activated manually from the bottom of the HP LaserJet 3100/3150 product. The switch causes the print engine to perform a self-diagnostic which bypasses the formatter 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. (See the “Engine test” section of Chapter 6, “Troubleshooting,” for more information about engine tests.)

Motor

The motor is controlled by the ECU. The motor provides all of the printer's paper movement.

EN

ECU/power system 69