Checking The Potential System - Canon NP6251 Service Manual

3.

Checking the Potential System

START
Select non-potential mode. ( 4 ;
* *
'PO.CONT' '1')
NO
Has the image improved?
YES
Turn off the power switch.
Short J127-1 and -2 on the DC
controller PCB with a jumper wire.
Disconnect J103.
(zero-level check)
Turn on the power switch.
Start service
mode ( 4 ). Is the indication
* *
NO
of address P023 during initial Replace the DC controller PCB.
rotation between
'0003' and
'001B'?
YES
Turn off the power switch.
Remove the jumper wire used to
short J127-1 and -2 on the DC
controller PCB. Connect J103.
Turn on the power switch.
Check to make sure that power is
on the potential measurement PCB,
and replace the potential
measurement unit.
<Transfer Output>
Is the
toner image on the
NO
photosensitive drum before
transfer normal?
YES
Select non-potential control mode.
( 4 .CONT' '1')
* *
Measure the voltage during
copying between J114A-6 (+) and
A-13 (-) on the DC controller PCB.
(transfer output)
Start service mode ( 1 ), and
* *
select 'TC' (transfer charging
assembly current). Convert the
reading (unit: µA) into its control
voltage as shown in 4 "Potential
Control Conversion Table."
Is the
actual measurement of
NO
Replace the DC controller PCB.
step A and the reading of 'TC' in
service mode ±10%?
YES
Replace the
high-voltage transformer.
YES
Is the problem corrected?
NO
Check the transfer charging
assembly for leakage. Try changing
the setting of 'FUZZY' in service
mode ( 5 ). Try replacing copy
* *
paper.
<Scanning Lamp Output>
Select potential control mode.
( 4 ; 'PO.CONT' '0')
* *
Turn on the power switch.
Select the activation voltage limiter
of the scanning lamp( 1 ; 'LIMT').
* *
Is 'LIMT' '1'?
YES
Clean the standard white plate,
mirror, lens, and dust-proofing
glass; then, turn off and on the
power switch.
Is 'LIMT' '1'?
YES
Select non-potential control.
( 4 ; 'PO.CONT' '1')
* *
End.
Measure the voltage during copying
between J111B-7 (+) and B-8 (-) on
the DC controller PCB.
A
B
NO
NO
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