Abstract: A xerographic device having a reusable photoconductor which is subjected in repeating cycles to (1) a charge corona whereat the photoconductor is uniformly charged to a negative voltage, (2) an imaging station whereat a working portion of the photoconductor is selectively discharged, to leave a charged area on this working portion defining a negative electrostatic latent image to be reproduced on copy paper, (3) a magnetic brush developing station whereat negatively charged carrier beads transport positively charged toner to the photoconductor's latent image, to leave a toned image on the photoconductor, (4) a transfer station, including a negative transfer corona, whereat a portion of the photoconductor's toned image is transferred to copy paper, (5) a positive preclean corona whereat the negatively charged photoconductor and its positive residual toner are subjected to a positive charge, and (6) a cleaning station whereat the photoconductor is cleaned by a brush having an affinity for positively charged par

Abstract: An electrophotographic copier's magnetic brush roller applies developer material to the surface of a photoconductor drum. Two parallel centerlines define the photoconductor drum surface a fixed gap distance from the magnetic brush roller's mating surface. Moving the magnetic brush roller adjusts the gap distance between the mating surfaces. Two sandwiches of conventional, standard-thickness, flexible, plastic sheets form tools; one having a total thickness slighty larger than the desired gap between the mating surfaces of the drum and roller, and the other having a thickness slightly less than the desired gap. The desired gap is set by separating the drum and roller surfaces, inserting the tool that is slightly smaller than the gap and closing the gap sufficiently so that each of the mating surfaces on the drum and roller contacts one surface of the tool.