Controls - Canon MF720 Series Service Manual

Controls

■ High-voltage power supply control
● Overview
The high-voltage power supply PCBs are to apply high-voltage bias to the primary charging roller, the primary transfer pad, the
secondary transfer external roller, and the ITB cleaning unit. Such high-voltage bias is generated through control by the DC
controller on the high-voltage power supply PCBs.
The figure below shows the high-voltage power source schematically.
Type Bias applied
Primary charging bias DC negative
Developing bias DC negative
Blade bias DC negative
Primary transfer bias DC negative
Secondary transfer bias DC positive
DC negative
ITB cleaning brush bias DC positive
ITB cleaning roller bias DC positive
Cleaning blade
Photosensitive
drum
Sweeper strip
Charge the photosensitive drum surface negatively.
Deposit toner on the static latent image formed on the
photosensitive drum.
Adjust the charged toner amount on the developing cylin-
der.
Transfer the toner image on the photosensitive drum to the
ITB.
Transfer the toner image on the ITB to the paper.
Clean the secondary transfer external roller.
Charge the toner on the ITB positively.
Charge the toner on the ITB positively.
Waste toner container
Purpose
35
2. Technical Explanation
Applied to
Primary charging roller (car-
tridge)
Developing cylinder (cartridge)
Developing blade (cartridge)
Developing blade (cartridge)
Secondary transfer external roll-
er
ITB cleaning brush
ITB cleaning roller