User Guide

Basic operation of the printer
Printer operation can be divided into four systems: the control system (which includes the power
supply and dc controller PCA), the pickup and feed system (which consists of various rollers and
transports the media through the printer), the laser/scanner system (which forms the latent image on
a photosensitive drum), and the image formation system (which transfers a toner image onto the
print media).
Printer operating sequence
A microprocessor on the dc controller PCA controls the printer operating sequence. The table Table
5-1 Basic printer operating sequence describes the basic operating sequence from when the printer
power is turned on until the final printed page is delivered to an output bin. For information about the
timing of the basic operating sequence, see
General timing diagrams.
Table 5-1 Basic printer operating sequence
Period (sequence) Description
Waiting The period of time from when the printer power is turned on until the main motor (or the
drum motor in the HP LaserJet 4250/4300/4350 only) begins to rotate. During this time the
transfer roller is cleaned and the microprocessor on the dc controller PCA checks to
determine if a print cartridge is installed in the printer.
Standby The period of time from the end of the waiting sequence or from the end of the last rotation
until a print command is received from the host computer or until the printer power is turned
off. The message Ready appears on the control-panel display.
Initial rotation The period of time when the photosensitive drum is stabilized to prepare for printing.
Print The period of time from the initial rotation until the control system detects a page entering
the printer (the top of page sensor [PS103] detects the page).
Last rotation The period of time from the completion of the print job until the main motor (or drum motor,
in an HP LaserJet 4250/4300/4350) stops. The final page of the job is delivered to an output
bin and the transfer roller is cleaned. If another print job is immediately detected, then the
printer returns to the initial rotation period. If no print jobs are waiting, then the printer returns
to the standby period.
Control system overview
The control system consists of the power supply and the dc controller PCA. It controls the pickup-
and-feed, laser/scanner, and image-formation systems. The microprocessor on the dc controller PCA
controls the printer operating sequence.
When the printer power is in the standby sequence (see
Table 5-1 Basic printer operating
sequence), the power supply supplies direct current power (dc voltage) to the dc controller PCA.
When the printer is in the standby sequence (see
Table 5-1 Basic printer operating sequence) the
microprocessor on the dc controller PCA sends signals to turn on and off various solenoids, motors,
and other printer components that process and print the image data that the host computer sends.
Introduction 105