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Q2431-90912 Chapter 5 Theory of operation 67
Introduction
This chapter presents an overview of the relationships between major components in the printer.
It also provides a general description of the following:
● Basic operation of the printer
● Power supply
● Laser/scanner assembly
● Image formation
● Paper pickup and feeding
● 500-sheet feeder operation
● 1,500-sheet feeder operation
● Envelope feeder
● Duplexer
● Stacker and stapler/stacker
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), the image formation system (which transfers a toner image
onto the print media), and.
Printer operating sequence
The operating sequence is controlled by a microprocessor on the DC controller PCA. The table
in this section 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 “HP LaserJet 4200 general timing diagram” on page 357 and
“HP LaserJet 4300 general timing diagram” on page 358.
Table 30. Basic printer operating sequence
Period (sequence) Description
Waiting This is the period of time from when the printer power is turned on until the main
motor or drum motor (HP LaserJet 4300 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 card ridge is installed in the printer.
Standby This is the period of time from the end of the waiting sequence until the print
command is input from the host computer, or from the end of the last rotation is
input from the sequence (described below) until a print command host computer,
or until the printer power is turned off. The message READY appears on the control-
panel display.
Initial rotation This is the period of time when the photosensitive drum is stabilized to prepare for
printing.
Print This is the period of time from the initial rotation until control system detects the
page entering the printer (the page is detected by the top of page sensor (PS103).
Last rotation This is the period of time from the completion of the print job until the main motor
or drum motor (HP LaserJet 4300 only) 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 (sent by the host computer) the printer returns to the initial
rotation period. If no print jobs are waiting, then the printer returns to the standby
period.