HP LaserJet 4250 Service Manual - Page 131

As the pre-feed sensor (PS102) detects the media, the dc controller PCA turns off the clutch, which stops the media. When the dc controller PCA detects that the laser/scanner is ready it activates the feed clutch again. The feed roller moves the media farther into the printer. The registration shutter corrects page skew and the media is transported to the fuser/delivery block. For information about the timing of these operations, see General timing diagrams. Printing from tray 1 The tray 1 paper sensor (PS105) detects the presence of media in tray 1. When the dc controller PCA receives the print command, the printer starts the initial rotation phase, which consists of main motor warm-up, scanner motor warm-up, high-voltage control sequence, and fuser warm-up. When the initial rotation phase ends, the tray 1 pickup solenoid (SL102) is activated. The cam rotates, the paper-tray lifter rises, and the media comes in contact with the tray 1 pickup roller. At the same time, the tray 1 pickup roller rotates twice and picks up a sheet of media from tray 1. The separation pad prevents additional sheets from feeding with the first sheet. The sheet then reaches the registration assembly, where its skew is corrected. The sheet then passes through the transfer, separation, and fusing stages; through the delivery unit; and is to the output bin. NOTE If media is removed from tray 1 after the initial rotation phase, but before the pickup roller pulls the media from the tray, the tray 1 pickup roller might continue to rotate up to six times, after which a jam detected. Paper-pickup-and-feed system 117