The printer uses an electrophotographic imaging system based on LED array technology. Two key components of the printer are the image generation system (IGS) controller and the printer control logic (PCL) board.
Image Generation System (IGS) controller: Each printer is equipped with an IGS con- troller, which provides the interface between the host computer, the PCL board, LED printhead, and the disk drives. The controller may be an EIGS or RIGS board.
Printer Control Logic (PCL) board: The PCL board directs the mechanical functions of the printer and print cycle timing. The PCL board also receives initial machine informa- tion, such as empty paper cassettes, paper jams, and fuser unit problems.
The illustration on the following page details the printing process. The numbers represent the sequence of events from the time that the system interface receives data, through the production of a print image, to the preparation for another print.
1Receiving data
Data from the host is received by the Signal Interface (SI) PCA and is passed to the Image Generating System (IGS) PCA, which temporarily stores the data in RAM. The data may consist of information generated on the host computer and sent over the host communication interface or it may consist of information generated by printer soft- ware, such as a request for test prints or to print the directory of a diskette.
2Bit Image
The IGS transforms the host file into a bit map image of 1s and 0s and stores them in user bitmap RAM. Bitmap memory is nothing more than an electronic piece of paper.
3Charging the photoconductor belt
When the IGS controller has a full page of data, it causes the PCL board to turn on the main motor, which rotates the photoconductor belt. As the photoconductor belt rotates, the main charger applies a high negative charge to it, which repels toner from the photoconductor belt except in the areas to print.
4Exposing the image
The negatively charged belt then passes the LED printhead, where the IGS controller turns the LEDs on and off to discharge the areas of the belt at a density of 300 dots per inch. The 1s in the bitmap memory turn the LEDs on; 0s turn the LEDs off. The dis- charged areas create a latent mirror image of the print on the photoconductor belt.
5Developing the image
As the photoconductor belt continues to rotate, it brings the latent image to the developer unit. A negative developer bias is applied to toner and the toner is transferred to the surface of the photoconductor belt. The negatively charged toner (which clings to small metal carrier beads) is attracted to the discharged areas of the belt. The carrier beads do not transfer. The belt, with the developed image on its surface, rotates out of the developer unit. At this time you can remove the photoconductor belt and read what is printed on it, which you may need to do when troubleshooting print problems.
Printer and Troubleshooting Overview |