If it's over toning, make sure the developer and PM don't need done. Clean the ID sensors, coronas, grid and housings. Then run all of the drum adjustments properly.
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Reset your Imaging units for Bizhub and CF series.
C350/C351/C450/C451/C550/C650
CF1501/CF2001/CF2002/CF3102 http://www.chipreset.eu