HP LaserJet 4250 Service Manual - Page 145

1,500-sheet feeder lifting mechanism The lifting mechanism maintains the media-stack surface at a specific position inside the 1,500-sheet feeder. So that the feeder can perform a stabilized pickup operation regardless of the size of the media in the feeder. Two wire cables lift the lift plate inside of the feeder. A motor (M1) uses pulleys in the feeder to wind the wires. When the front door of the feeder is opened, the pulley gears and the motor gear are disengaged and the lift plate lowers under its own weight. The lifting mechanism is active (the plate is in the raised position) when the dc controller PCA sends a signal, when the front door is closed, or during the print operation. The 1,500-sheet feeder control PCA driver stops the motor (M1) when the 1,500-sheet feeder paper-stack-position sensor (SR2) detects media. If the 1,500-sheet feeder paper-stack-position sensor (SR2) does not detect media within approximately 30 seconds after the start of the lift operation, the paper-deck driver PCA detects a lifter motor failure and sends a signal to the dc controller PCA. An error message appears on the control-panel display. Figure 5-14 1,500-sheet feeder lifting mechanism Paper-pickup-and-feed system 131