Theory-12:-Laser Printer Components

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.