Canon PC940 Service Manual - Page 102
Controlling the Transfer Roller Bias, Outline
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CHAPTER 4 IMAGE FORMATION SYSTEM D. Controlling the Transfer Roller Bias 1. Outline The circuit shown in Figure 4-105 is used to control the voltage applied to the transfer charging roller, and has the following functions: • Turning on and off the transfer bias. • Controlling the transfer bias to a constant voltage. • Correcting the transfer bias voltage level (ATVC) • Switching the transfer bias polarity (cleaning bias) Main transformer Transfer positive DC bias generation circuit T101 (Q101) (Q900) Transfer positive DC bias ON signal T_REV_ON* Transfer overcurrent detection signal HV_LIMIT Transfer current detection signal T_FW_S Transfer bias voltage detection signal Transfer bias T_FEEDBACK detection circuit Microprocessor Microprocessor Serial communication Transfer DC bias control signal T_FW_DRV Transfer bias control circuit Transfer DC bias ON signal T_FW_ON High-voltage transformer control signal CLK32K +24V T302 Transfer high-voltage transformer Photosensitive drum Transfer charging roller DC controller PCB Figure 4-105 Composite power supply PCB 4-8 COPYRIGHT © 1999 CANON INC. CANON PC800s/900s REV.0 AUG. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)