Toshiba 4580, Service Manual

Page: 185 / 379

6570/5570 DRUM 10 - 2 Mar. 1999 © TOSHIBA TEC
10.2 Functions
(1) Drum
The drum comprises a drum-shaped, Aluminum base coated with an organic photosensitive element
(photoconductor) film. The principle of “Photoconductivity” indicates that insulating properties of the
material are evidenced in the dark. Likewise, its conductive properties are evidenced in the presence
of light.
(2) Main Charger
The main charger is configured by stretching a special wire between two insulation blocks provided
at both ends of a u-shaped metal bracket. When high voltage is applied to this charger wire, the air
around the wire is ionized (electrostatically charged). The ionized air is attracted to the drum’s sur-
face. This phenomenon is referred to as “corona discharge.” In the dark, the surface of the drum is
negatively (minus) charged using the principle of corona discharge.
(3) Charger wire cleaner
The charger wire cleaner moves backwards and forwards to clean the charger wire after the power is
turned ON and after more than 2000 continuous copies have been made since the door switch is
turned ON or from the previous cleaning operation.
(4) Discharge LED
“Discharge” refers to the process of reducing or eliminating the electrostatic charge left on the photo-
sensitive element after the charging and the transfer processes. The function of the discharge LED is
to lower the electrical resistance of the photosensitive surface that was left over after the exposure
and transfer processes. The LED device is a light source. The LED has two effects, a cleaning effect
and “pre-exposure” effect. The cleaning effect neutralizes and eliminates the residual charge on the
surface of the photosensitive element while the pre-exposure effect maintains a fixed photosensitive
surface potential before the charging process is again initiated.