I-7
Black and blurred horizontal stripes
Possible cause
Step
Check
Result
Remedy
Scratch on the
drum
1
Are the horizontal stripes at 94mm
intervals?
Yes
Replace the drum
unit.
Toner stuck on
the develop
roller
2
Are the horizontal stripes at 17mm
intervals?
Yes
Print several sheets
and see what
happens.
The problem will
disappear after a
while.
Scratch on the
fixing roller
3
Are the horizontal streaks at 50 mm
intervals?
Yes
Replace the fixing
unit.
I-8
Dropout
Possible cause
Step
Check
Result
Remedy
Transfer failure
1
Is the transfer roller soiled? Is it
scratched?
Yes
Replace the drum
unit.
High-voltage
power supply
failure
2
Open the top cover and measure
the voltage at the transfer electrode
plate at the right side while printing
with the interlocks defeated.
Is the voltage correct?
Yes
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.
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 ...