2.2
Troubleshooting Image Defects
Procedures to be followed in the event of specific image defects.
I-1
Light
Possible cause
Step
Check
Result
Remedy
Scanner
window
1
Is the scanner window dirt?
Yes
Clean the scanner
window with a soft
dry cloth.
Poor contrast
2
Is the contrast adjustment dial in the
center of the click position?
No
Set it to the center
click position or
reasonable position.
Toner sensing
failure (toner
cartridge side)
3
Is the problem solved when 4 or 5
pages are printed after the cartridge
is replaced with a full one?
Yes
The wiper of the
toner cartridge is
defective. Replace
the toner cartridge.
Toner sensing
failure (printer
side)
4
Can printing be started with the
drum unit removed?
Yes
Toner sensor failure.
Check if the toner
sensor needs
cleaning and check
the toner sensor
connection.
Drum
connection
failure
5
Is the drum shaft connected with
electrode when the drum unit is
installed?
No
Clean contact
electrodes between
the printer body and
the drum shaft of
drum unit.
Transfer
electrode
contact failure
6
Is there continuity between the
transfer roller shaft and the transfer
electrode on the external drum unit?
Yes
Remove the transfer
roller and clean the
contact electrode.
Clean the external
electrode.
Transfer failure
7
Is the problem solved when the
transfer roller is replaced?
Yes
Replace the drum
unit.
Developing bias
contact failure
8
Are the developing bias contacts
between the printer body and the
drum unit soiled?
Yes
Clean the terminals
of both sides.
High-voltage
power supply
failure
9
Open the top cover and measure
the voltage at the electrode plate at
the right side face while printing
defeated.
Is the voltage correct?
No
Check the harness
connection between
the high-voltage
power supply and
the panel sensor
PCB.
If the connection is
normal, replace the
high-voltage power
supply PCB.
Panel sensor
PCB failure
10
Perform the same check as step 8
above.
No
Replace the panel
sensor PCB.
Summary of Contents for HL-720
Page 1: ...SERVICE MANUAL MODEL HL 720 730 730Plus R LASER PRINTER ...
Page 36: ...II 19 1 3 10 Engine I O HL 720 Fig 2 21 shows the engine interface circuit Fig 2 21 ...
Page 37: ...II 20 HL 730 730Plus Fig 2 22 shows the engine interface circuit Fig 2 22 ...
Page 61: ... Fig 3 18 2 4 1 1 1 ...
Page 92: ...SERVICE MANUAL MODEL HL 760 R LASER PRINTER ...
Page 109: ...II 8 1 3 4 DRAM Two 4M bit DRAMs x 16bits are used as the RAM Fig 2 6 ...
Page 113: ...II 12 1 3 10 Engine I O Fig 2 12 shows the engine interface circuit Fig 2 12 ...
Page 114: ...II 13 1 3 11 Paper Feed Motor Drive Circuit Fig 2 13 ...
Page 133: ...Appendix 2 Main PCB Circuit Diagram 1 3 CODE UK3227000 B48K272CIR 1 3 NAME ...
Page 134: ...Appendix 3 Main PCB Circuit Diagram 2 3 CODE UK3227000 B48K272CIR 2 3 NAME ...
Page 135: ...CODE UK3227000 B48K272CIR 3 3 NAME Appendix 4 Main PCB Circuit Diagram 3 3 ...