COPYRIGHT © 1999 CANON INC. CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)When all is ready, the duplexing driver PCB drives the horizontal registration motor fora specific number of pulses based on the paper size data from the DC controller PCB toshift the horizontal registration guide according to the size of the paper for horizontal reg-istration (Note).The horizontal registration guide returns to its home position a specific period of timeafter the leading edge of paper is moved and detected by the duplexing unit paper sen-sor (PS24). The horizontal registration motor (M7) is a stepping motor, capable of con-trolling the shift distance with high accuracy.The duplexing driver PCB will identify a fault in the registration guide if the shift dis-tance exceeds the value stored in advance (i.e., the distance the horizontal registrationguide moves from its home position), communicating the fact to the printer board*1 byway of the DC controller PCB.*1 Reader controller PCB (when making prints with the reader unit installed).Reference:E055: A fault in the drive of the duplexing unit horizontal registration guide.CHAPTER 5 PICK-UP/FEEDING SYSTEM5-27Note:If the paper is not A3, 11x17, A4R, LTRR, or B4, the horizontal registration guide mustmove a longer distance. As such, the duplexing driver PCB drives the horizontal reg-istration motor (M7) while the reversing roller is rotating counterclockwise to move thehorizontal registration guide to a point suited to the paper size.Download free service manual at http://printer1.blogspot.com