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ECU/power system
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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.