Technology of the IBM 3800 Printing Subsystem Model 3
by D. McMurtry, M. Tinghitella, R. Svendsen
IBM has introduced the 3800 Model 3 electrophotographic printer, which is a modified version of the previously developed Model 1. The Model 3 improves the print density of the 3800 Model 1 from 180×144 pels/in.2 to 240×240 pels/in.2 and permits each pel to be addressed individually. The laser print head was modified to create the higher density by using the same laser, focusing to a smaller spot size, slowing down the speed of the rotating mirror, and developing a dual-beam system. Beam-power balance and beam separation were selected for optimum print quality. The dual-beam print head required the development of a new photoconductor with improved sensitivity. That photoconductor also displayed a significantly increased lifetime. Improved manufacturing techniques were developed to reduce photoconductor defects. A digital voltmeter and a new processor were introduced that reduced the cost of the process servos by eliminating previously hard-wired elements.