HP LaserJet 9040/9050 Service Manual - Page 110

Pickup and feed The tray 1 pickup unit picks up media by lowering the pickup roller onto the surface of the media that is loaded in the tray, and then separating the roller from the media surface the pickup cam lifts the pickup roller up and down. When the tray 1 pickup unit turns on the pickup solenoid, the stopper leaves the cam, allowing the cam to rotate. This shifts the pickup roller up and down. After completing one rotation, the cam contacts the stopper and is held in so the pickup roller is brought to its initial position. Tray 1 utilizes the separation roller method for its multiple-feed-prevention mechanism. This method drives the feed rollers and separation roller in the reverse direction from each other. The separation roller contains a torque limiter. When a multifeed occurs, the torque limiter allows the top sheet to feed into the printer, but returns the additional sheet to the tray. Jam detection The tray 1 paper path sensor (PS2502) determines whether or not media is transported correctly to the printer. If the paper path sensor does not detect the leading edge of media within the specified length of time after turning on the pickup solenoid, the CPU stops the pickup operation and notifies the DC controller of a jam occurrence. The CPU in tray 1 detects the following jams: z Pickup retry. If the paper path sensor does not detect the leading edge of media 1 second after turning on the pickup solenoid, the CPU stops the motor once, and then restarts it. The CPU turns on the pickup solenoid 0.7 seconds after the start of the second motor rotation. z Pickup delay jam. The paper path sensor (PS2502) does not detect the leading edge of media within 3 seconds of turning on the pickup solenoid. z Residual jam. There is power to tray 1, the top cover is closed (or when the tray returns from sleep mode), and the paper path sensor (PS2502) detects media. 94 Chapter 5 Theory of operation