Brother International HL-720 Service Manual - Page 67

All black, See item I-2.

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I-4 All black Possible cause Corona failure Ditto Ditto Step 1 2 3 Check Is the drum unit corona wire broken? Are the charging terminal spring at the printer body side and the electrode on the bottom face of the drum unit dirty? When printing is performed with the interlocks defeated, is the specified voltage measured at the charging spring at the printer body side? Ditto 4 Perform the same check as in step 3. Result No Yes Remedy Replace the drum unit. Clean the charging wire at the both sides. Yes Check the connection of the harness between the high-voltage power supply and the panel sensor PCB. No Replace the panel sensor PCB. I-4 All black Possible cause Soiled fixing unit Step 1(A) Check Is the area of about 50mm from the top on the back of paper soiled? Soiling of the transfer roller Fogging 1(B) Is other area rather than the above soiled? 2 Is the transfer roller soiled? 3 Is the back of the paper fogged? Result Yes Yes Yes Yes Remedy No failure on the fixing unit, clean the transfer roller. (See below.) Replace the fixing unit. Replace the drum unit. See item I-2.

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I-4
All black
Possible cause
Step
Check
Result
Remedy
Corona failure
1
Is the drum unit corona wire
broken?
No
Replace the drum
unit.
Ditto
2
Are the charging terminal spring at
the printer body side and the
electrode on the bottom face of the
drum unit dirty?
Yes
Clean the charging
wire at the both
sides.
Ditto
3
When printing is performed with the
interlocks defeated, is the specified
voltage measured at the charging
spring at the printer body side?
Yes
Check the
connection of the
harness between the
high-voltage power
supply and the panel
sensor PCB.
Ditto
4
Perform the same check as in step
3.
No
Replace the panel
sensor PCB.
I-4
All black
Possible cause
Step
Check
Result
Remedy
Soiled fixing unit
1(A)
Is the area of about 50mm from the
top on the back of paper soiled?
Yes
No failure on the
fixing unit, clean the
transfer roller.
(See below.)
1(B)
Is other area rather than the above
soiled?
Yes
Replace the fixing
unit.
Soiling of the
transfer roller
2
Is the transfer roller soiled?
Yes
Replace the drum
unit.
Fogging
3
Is the back of the paper fogged?
Yes
See item I-2.