Canon iR5570 Series Service Manual Download

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Chapter 13

13-11

F-13-12

13.1.6 Checking the Surface Potential Control System

0008-7914

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.

When the machine is in non-auto control mode, all settings used for corona current control, laser power control, and developing bias control will be

automatically be set to default settings.

Using Non-Auto Control Mode

1)Make the following selections in service mode, enter '0', and press the OK key:

COPIER>OPTION>BODY>PO-CONT.

2) Press the Reset key twice.

3. Making a Zero-Level check

A "zero-level check" is a check made to see if the control mechanism of the DC controller PCB is identifying a 0-V level without fail when the drum

surface potential is 0 V.

A zero-level check may be made in either of 2 ways, and you can use it to decided whether the DC controller PCB and the potential measurement

PCB is free of error:

Method 1: use it to find out if the level shift circuit on the DC controller PCB is free of a fault

Method 2: use it to find out if the potential control circuit is free of a fault

(1) Method 1

1) Turn off the main power switch.

2) Remove the upper rear over.

3) Short GP33 on the DC controller PCB and GND using a cable equipped with an alligator clips or probes on both ends.

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

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."

Canon iR5570 Series, Service Manual

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