Canon iR6570 series, Portable Manual

Page: 46 / 320

Chapter 2
2-12
F-2-12
2.1.6 Checking the Surface Potential Control System
0008-7914
iR5570 / iR6570
1. Outline
If an image fault occurs, it is necessary to find out whether the cause is in the static image formation block
including the photosensitive drum and the potential control system or if it is caused at time of development or
transfer.
An image fault may be isolated by finding out whether the surface potential is correct using service mode.
2. Disabling the Auto Control Mechanisms
As a means of checking the potential control system, the auto control mechanism may be disabled (hereafter,
non-auto control mode).
If the image fault in question is more or less corrected when the machine is in non-auto control mode, you can
suspect the potential measurement unit and the DC controller PCB as the cause of the fault.
You can also take advantage of non-auto control mode as a tentative remedy when the auto control mechanism
has a fault.
Check the developing assembly
for leakage; if normal, go to a
check on the transfer output.
Make the following selections (DC
value of the developing bias):
COPIER>DISPLAY>HV-STS>BIAS.
Covert the indication during printing
(V) into a control voltage with
reference to "Potential Control
Conversion Table."
Is the
deferense between
the actual measurement of
HVT_DEV-BIAS_DC and 'BIAS'
in service mode
± 10%?
YES
NO
Checking the Developing Bias Output
1) Check the transfer charging assembly for
leakage.
2) Make the following selections in service
mode, and try changing the setting:
COPIER>OPTION>BODY>FUZZY.
3) Try replacing paper.
Make the following selections in service mode
(level of current of transfer charging). Convert
the reading (mA) during printing into a control
voltage based on 8.5 "Potential Control
Conversion Table."
Replace the
photosensitive
drum.
NO
YES
NO
YES
NO
Is the
difference between
the measurement of HVT_
TRANSFER and 'TR' in
service mode
+/- 10%?
Checking the Transfer Output
Is the toner
image on the photosensitive
drum before transfer
normal?
Replace the
high-voltage transformer.
Is the problem
corrected?
YES
Replace the
DC controller
PCB.
Replace the
DC controller
PCB.
END
Enable potential control: COPIER>
OPTION>BODY>PO-CNT=1
B
Measure the voltage HVT_DEV_BIAS
_DC during printing of J102A-8 on the
DC controller PCB.
Disable the potential control mechanism
by setting '0' for the following:
COPIER>OPTION>BODY>PO-CNT.
Measure the voltage HVT_TRA during
printing of J102A-12 on the DC
controller PCB.