Oki B 4100 Maintenance Manual page 528

The EP (image) drum surface is charged to about -750 V by the contact charge of the charge
roller.
When light from the LED head irradiates the EP (image) drum surface, the light energy generates
positive and negative carriers in the CGL. The positive carriers are moved to the CTL by an
electrical field acting on the EP (image) drum. Likewise, the negative carriers flow into the
aluminum layer (ground).
The positive carriers moved to the CTL combine with the negative charges on the EP (image)
drum surface accumulated by the contact charge of the charge roller, lowering the potential on the
EP (image) drum surface. The resultant drop in the potential of the irradiated part of the EP
(image) drum surface forms an electrostatic latent image on it. The irradiated part of the EP
(image) drum surface is kept at about -100 V.
surface potential
40055101TH Rev.4
(V)
–750
EP drum
–100
0
Charged part
Light
from
LED
Part Charged
irradiated part
by
LED
528 /