Canon imageRUNNER ADVANCE C255 Series, Service Manual, Page: 339 / 987

Field Remedy
Execute the following service mode to change the setting of the fixing speed when feeding envelopes.
( Lv.2 ) COPIER > OPTION > FEED-SW > EVLP-FS
With this setting, the fixing speed when feeding envelopes can be specified within the range of -2.0% to +2.0%. (Setting range:
-20 to 20)
There is a possibility of image displacement at the envelope's trailing edge, therefore change the setting value while checking
the wrinkle and the image displacement.
■ Dark Spots on the Halftone Image
Location
The initial ITB (the surface resistance is high) and the Drum Unit at the end of its life (the charging amount of toner is low)
Cause
When a halftone image is output, dark spots may occur locally. It does not occur in Bk color.
A slight amount of Bk developing carrier [1] is normally attached to the surface of the Bk Drum [2]. On the other hand, when the
color toner image [a] on the ITB [3] that has passed through the Y Drum, M Drum, and C Drum reaches the Bk Drum [2], a part
of the surface is slightly transferred on to the Bk Drum [2]. (This transfer symptom is hereafter referred to as retransferring.)
The amount of toner retransferred here becomes smaller in the area [b] on the surface of the Bk Drum [2] where the developing
carrier is attached. On the other hand, in the area [c] on the ITB [3] where the developing carrier had been attached, toner form
a lump and the amount of toner becomes larger.
For this reason, when the toner image on the ITB [3] is secondarily transferred to paper, the lump area [c] appears as a dark spot.
[3]
[1]
[b]
[c]
[a]
[2]
Condition
This tends to occur when the initial ITB (the surface resistance is high) and the Drum Unit at the end of its life (the charging amount
of toner is low) are used in a low humidity environment.
6. Troubleshooting
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