HP LaserJet M9040/M9050 Service Manual - Page 140

Pickup roller home position control operation The pickup roller home position control operation sets the pickup roller at its home position as an advance preparation to allow the roller to pick up the document. 1. The SCB monitors the pickup home position detection sensor (PICK-S) to detect the home position. 2. At the initial operation, or after delivering the document, the SCB rotates the pickup motor in the reverse direction and checks a signal from the PICK-S. 3. When the PICK-S detects the pickup home position lever on the shaft of the pickup roller, the SCB determines that the pickup roller is at its home position and stops the pickup motor. 4. When the SCB cannot detect the home position of the pickup roller within a specified period of time after the pickup motor starts rotating in the normal direction, the SCB recognizes the pickup motor failure and notifies the CP. A 30.1.9 error is shown on the control panel. ADF document size detection The sensors and the potentiometer send signals to the SCB, and these signals are transferred through the intermediate PCA to the CP. The CP calculates the size of the document based on the signals in the service menu. ADF document size detection terminology ● TRS-S: ADF document length detection (short) ● TRL-S: ADF document length detection (long) ● TRVR: ADF width detection unit (potentiometer) NOTE: The width detection unit can be calibrated in the service menu. Figure 5-21 ADF document size detection 122 Chapter 5 Theory of operation ENWW