Charging Mechanism; Controlling Pre-Exposure Led; Pre-Exposure Led Control - Canon iR5055 Series Service Manual

Chapter 7
1. Adjusting the Density for Copying
The machine increases the developing bias to decrease the copy density. If increased in excess, the bias can cause light images; if decreased in excess, on the other
hand, the background can developing fogging. In light of this, the machine executes density processing using changes in the developing bias and image processing
(binary density processing).
Purpose: to obtain the density suited to the user's needs.
Method of correction: uses the developing bias and image processing (binary density processing) according to the F-value setting.
F value
1
2
3
4
5
2. Adjusting the Density for Printing
The machine increases the developing bias to increase the print density. If increased in excess, the background can develop fogging. At the lower limit of the de-
veloping bias, the machine uses the changes in the developing bias and image processing (thickening processing) to ensure appropriate density.
Purpose: to obtain the density suited to the user's needs.
Method of correction: uses the developing bias and image processing (thickening) to suit the F-value setting.
F value
1
2
3
4
5
6
7
8
9
*1: Thickening processing may be enabled for all F values in user mode ('correct fine line').

7.5 Charging Mechanism

7.5.1 Controlling Pre-Exposure LED

7.5.1.1 Pre-Exposure LED Control

iR5065 / iR 5055 / iR5075 / iR5075N / iR5065N / iR5055N
The machine is equipped with a pre-exposure LED used to prevent adhesion of excess toner on the photosensitive drum because of residual charges. The following
is an item associated with the pre-exposure LED control system:
1. turning on/off the pre-exposure LED
7-8
Developing DC bias standard value
(V)
240
220
180
140
120
Developing DC bias standard
value (V)
218
205
194
182
170
153
137
120
120
T-7-5
Shift (V) Image processing
60 yes
40 no
0 no
-40 no
-60 yes
T-7-6
Shift (V) Thickening*1
48 no
35 no
24 no
12 no
0 no
-17 no
-33 no
-50 no
-50 yes
Image density
lighter
darker
Image density
light
dark
0015-4487