Samsung ML-451 Series Service Manual page 223

The toner level is not even on the imaging unit roller due
to the bad blade.
8) Background
Description : Light dark background appears in whole area of the printing.
Check and cause
Does recycle paper be used?
The life of the imaging unit has been expired
The output from the HVPS is abnormal.
9) Ghost
Description : Ghost occurs at 94.2 mm intervals of the OPC drum.
Check and cause
The high voltage terminal is contaminated.
The life of the imaging unit has been expired
The life of the transfer roller has been expired.
10) Stains on back of page
Description : The back of the page is stained.
Copyright© 1995-2016 SAMSUNG. All rights reserved.
4. Alignment and Troubleshooting
Replace the imaging unit.
Solution
Use the proper papers.
Replace the imaging unit.
Replace the HVPS board.
Solution
Clean the high voltage terminals.
Replace the imaging unit.
Replace the transfer roller.
4-122