Samsung ML-451 Series Service Manual page 221

3) Horizontal Black Band
Description : Dark of blurry horizontal stripes occur in the printing periodically.
Check and cause
Bad contacts of the voltage terminals to imaging unit.
The rollers of developer may be stained.
— OPC Drum = 94.2 mm
— Charge Roller = 44 mm
— Magnetic Roller = 56.6 mm
4) Black and White spot
Description : Dark or blurry black spots occur periodically in the printing.
Check and cause
If dark or blurry black spots occur periodically, the rollers in
the Imaging unit may be contaminated with foreign matte
or paper particles. (Charge roller : 44 mm interval / OPC
drum : 94.2 mm interval)
If faded areas or voids occur in a black image at intervals of
94.2 mm, the OPC drum surface is damaged.
If a black image is partially broken, the transfer voltage is
abnormal or the transfer roller's life has expired.
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4. Alignment and Troubleshooting
Solution
Clean each voltage terminal of the Charge, Magnetic,
Imaging unit and Transfer roller. (remove the toner particles
and paper particles)
Replace the imaging unit.
Solution
Clean each voltage terminal of the Charge, Magnetic,
Imaging unit and Transfer roller. (remove the toner particles
and paper particles)
Replace the imaging unit.
If the transfer roller's life is expired, replace it.
•
Clean the inside of the set against the paper particles
•
and foreign matter in order not to cause the trouble.
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