Canon imageRUNNER ADVANCE 4551i Service Manual page 106

■ Primary Charging Bias Control
The machine is directly charged by the charging roller. DC bias and AC bias that stabilized the charge is applied to the primary
charging roller.
No.
[1] Primary charging bias control signal
■ Constant voltage control of DC bias and AC bias
The primary AC bias control circuits on the DC controller PCB control the DC bias and AC bias applied to the primary charging
roller to keep their voltage at the fixed level.
The primary AC bias control circuits control constant voltage control and current quantity of electric discharge control of the AC
bias by the environment.
* The current quantity of electric discharge control minimizes charged AC bias to lengthen drum life. Electric discharge product
on the drum decreases by decreasing the primary AC bias. Therefore, the image smear by fusion with the water decrease.
■ DC/AC bias switch control
The DC/AC bias output varies according to the environment detected by the environment sensor (S16).
■ Drum Unit Detection (New/Old)
This machine reads information recorded in the Drum Unit Memory and detects whether the drum is new or old based on the
information, when the power is turned on.
When a new drum is detected, it is judged that the Drum Unit has been replaced.
Operation of the host machine
1. Check whether Drum Unit Memory is present in each drum unit.
Primary charging roller
HVT PCB
Environment sensor
[2] [1]
Primary AC bias
control circuit
Name
Photosensitive drum
Primary DC bias
control circuit
DC Controller PCB
No.
[2] Environment sensor detection signal
93
2. Technology
Name