Canon PC940 Service Manual - Page 336

CHAPTER 11 TROUBLESHOOTING 19 The scanner fails to move forward. Cause Cable Scanner path Composite power supply PCB Pre-registration roller paper sensor (Q751) Scanner/lens drive motor (M2) DC controller PCB Step 1 2 3 4 5 Checks Is the scanner drive cable routed correctly? Is the scanner rail soiled? Move the scanner by hand. Does it move smoothly? Set the meter range to 30 VDC, and connect the meter probes to J202-2 (+) and -1 (-) on the composite power supply PCB. Is the meter reading about 24 V? Is the pre-registration roller paper sensor (Q751) normal? (For instructions on how to check the photointerrupers, see p. 11-47.) Replace the scanner/lens drive motor (M2). Is the problem corrected? YES/NO NO NO NO NO YES Action Route the cable correctly. Check the surface of the scanner rail for dirt, foreign matter, or object which may interfere. See "DC power fails to turn on." Check the wiring from J108 on the DC controller PCB to Q751; if normal, replace Q751. End. NO Replace the DC controller PCB. 20 The registration roller fails to rotate. Cause Main motor (M1) Pre-registration roller paper sensor (Q751) Registration roller spring clutch Registration clutch solenoid (SL2) DC controller PCB Step 1 2 Checks Does the main motor (M1) start to rotate when the Copy Start key is pressed? Is the pre-registration roller paper sensor (Q751) normal? (For instructions on how to check the photointerrupers, see p. 11-47.) 3 Does the registration clutch solenoid (SL2) turn on for a moment after the Copy Start key is pressed? 4 Set the meter range to 30 VDC. Does the voltage between J109-6 (+) and -5 (-) on the DC controller PCB change to about 24 V for a moment after the Copy Start key is pressed? Yes/No No Action See "The main motor fails to rotate." No Check the wiring from J108 on the DC controller PCB to Q751; if normal, replace Q751. No Check the position of the solenoid; if normal, check or replace the control ring. Yes Check the wiring from J109 on the DC controller PCB to SL2; if normal, replace SL2. No Replace the DC controller PCB. COPYRIGHT © 1999 CANON INC. CANON PC800s/900s REV.0 AUG. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON) 11-71