HP LaserJet 4250 Service Manual - Page 140
-sheet feeder pickup and feeding, The pickup roller, when the solenoid activates
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500-sheet feeder pickup and feeding Three switches on the paper-feeder driver detect the media size and the presence of the 500-sheet tray. The relationship between the switch combinations and the paper sizes is the same as for the printer. The main motor (M101) drives the paper feeder. When the dc controller PCA sends a print command, the main motor begins to rotate. When the scanner motor reaches its prescribed speed, the paper-feeder driver receives the pickup command from the dc controller PCA and activates the paper-feeder pickup solenoid. (The main motor drives the pickup roller, feed roller, and separation roller.) The pickup roller, when the solenoid activates it, rotates once and picks up the media in the tray. The separation roller removes any additional sheets and the media travels to the pre-feed sensor (PS102). The sheet then reaches the registration assembly, where its skew is corrected. The sheet advances through transfer, separation, and fusing stages; passes through the delivery unit; and is delivered to the output bin. NOTE The 500-sheet feeder detects pickup-and-feed jams the same way the printer does. See Jam detection. 126 5 Theory of operation
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