Canon GP605 Service Manual page 638

CHAPTER 13 TROUBLESHOOTING
c. Zero-Level Check
A "zero level check" may be used as a means to find out the condition of the surface potential
control circuit.
Reference:
A zero-level check is to find out whether a microprocessor is reading 0 V when the surface
potential of the drum is 0 V.
A zero-level check enables a check on the microprocessor on the DC controller PCB and the
measuring unit, and it may be either of the following two ways; method 1 enables a check on the
level shift circuit on the DC controller PCB, while method 2 enables a check on the potential
measurement circuit:
1. Method 1
1) Turn off the power switch.
2) Short J522-1 and -2 on the DC controller PCB with a jumper wire, and disconnect the connec-
tor J3 of the potential control PCB.
13-46
COPYRIGHT © 1999 CANON INC.
J522
Figure 13-G202
Connector (J3)
CANON GP605/605V REV.0 JAN. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)