HP 8550 Service Manual - Page 527

The scanner motor fails to move forward or to move in reverse. Cause Cable Rail Step 1 2 Scanner home 3 position sensor (PS101) Connectors, 4 wiring Copy module dc power supply Scanner motor 6 driver PCB Scanner motor (PM1) Checks Yes/No Action Is the drive cable routed correctly? NO Route the cable correctly. Is the rail free of dirt? Does it NO move smoothly when moved by hand? Check the surface of the rail for dirt and foreign matter or some other obstacle; clean, lubricate, or correct as necessary. If the rail is soiled, clean it with alcohol, and apply a small amount of lubricant. Is the scanner home position NO sensor (PS101) normal? See the instructions for how to check the photo-interrupters. Check the wiring and lightblocking plate; if normal, replace the sensor. Are connector J301 on the NO scanner motor driver PCB and connectors J3, J5, and J6 on the copy module main power supply PCB connected securely? Connect the connectors securely. Measure the voltage between the NO following terminals of the scanner motor driver PCB. Is it as indicated? J301-9 and -8: about +5.2 V J301-7 and -6: about +15 V J301-5 and -6: about -12 V J301-4 and -2: about +38 V J301-3 and -1: about 38 V See "No dc power to the copy module" on page 520. Replace the scanner motor driver YES PCB. Is the problem corrected? End. NO Replace the scanner motor. EN Copy module troubleshooting 525