Laser Printer Components
The following are the main parts of a laser printer:
- Drum
- High‐voltage power supply
- DC power supply
- Paper transport
- Primary Corona
- Transfer Corona
- Fusing rollers
- Controller
Drum The drum inside
the toner cartridge is photosensitive, which means it reacts to light. The drum
holds an electrostatic charge (except where it is exposed to light). The laser
beam is reflected onto the surface of the drum to create a pattern of charged
and not-so-charged spots, representing the image of the page to be printed.
High‐voltage power
supply The process uses very high voltage to charge the drum and transfer and
hold the toner on the paper. The high-voltage power supply converts AC current
into the higher voltages used by the printer.
DC power supply Like a
computer, most of the electronic components in the laser printer use direct
current. For example, logic circuits use +5V DC (volts direct current), and the
paper transport motors use +24V DC.
Paper transport Inside
the laser printer are four types of rollers that move the paper through the
printer. Each rubberized roller or set of rollers is driven by its own motor.
The four roller types in the paper transport system are the feed, registration,
fuser and exit roller. This is where most paper jams in a laser printer occur.
Primary Corona Also
called the main corona, this device forms an electrical field that uniformly
charges the photosensitive drum to +600V to reset it prior to receiving the
print image and toner.
Transfer Corona This
mechanism moves a page image from the drum to the paper. The transfer corona
charges the paper; the charge pulls the toner from the drum onto the paper. As
the paper exits the transfer corona, a static charge eliminator strip reduces
the charge on the paper so that it won't stick to the drum. Not all printers
use a transfer corona; some use a transfer roller instead. When working on a
printer with a transfer roller, be careful not to touch the roller. The oils
from your skin can spot the transfer roller and cause improperly charged paper,
resulting in defects in the printed image.
Fusing Rollers The
toner is melted permanently to the page by the fusing rollers that apply
pressure and heat (between 165 and 180C) to it. The fuser - not the laser -
makes the printed pages hot.
Controller This is the
motherboard of the laser printer, and it has architecture and components like a
PC motherboard. The controller communicates with the PC, houses the memory in
the printer, and forms the image printed on the page. Memory expansion is
possible on virtually all laser printers. Adding memory allows the printer to
reproduce larger documents or graphics in higher resolutions or to support
additional soft fonts.
A printer that
experiences frequent memory overflow errors may require more memory or has a
bad memory board. Check what was being printed when the fault occurs, as memory
overflow is more likely to be the cause.
