Canon iR5570 Series, Service Manual

Page: 206 / 684

Chapter 7
7-8
F-7-9
7.4.4 Determining the Laser Output
0009-3543
To measure the light area potential (VL1) for the first time after the power switch is turned on, the machine uses the most recent laser output level (LP0),
and measures the drum surface potential using the potential sensor. The DC controller PCB compares the drum source potential and the target potential;
if the measured potential is +/-10V of the target value, the machine corrects the potential of the laser output, and measures the potential once again. The
machine executes potential measurement a maximum of 8 times, and also corrects the lower output level as many times. In addition, the machine measures
the light area (VL2) for the developing bias for use in determining the laser output (LP) needed to attain the target potential.
F-7-10
7.4.5 Determining the Developing Bias
0009-3544
The machine determines the developing bias (VDC) as follows with reference to the drum surface potential (VL2):
VDC = VL2 + delta VDC
For copier potential, delta VDC=110 V
For printer potential, delta VDC=85 to 110 V (i.e., the printer potential varies to suit the reading of the environment sensor, thus ensuring the reproduction
of correct line width)
WMUPR WMUP STBY
200 C
Potential sensor
Primary charging
Grid bias
Vpc Vpc Vpc Vpc
VD
+6V
-6V
VD
VD
Correction control
sequence start
Potential control
sequence start
Previous potential
VD VD VD VD VD VD
Target VD
Fixing assembly temperature 195 C
WMUPR
WMUP STBY
200˚C
Potential sensor
Developing bias
(DC)
Laser
LP0
LP0 LP0 LP0 LP0
LP
VL1 VL1 VL1 Target VL1 VL1 VL1
Correction control
sequence start
Fixing assembly
temperature 195 Deg C
VL1
+6V
-6V
VL1
VL1
VL1
Previous potential
Target VL1
Potential control
sequence start
VL2