Color Spots (Black Spots) - Konica Minolta AccurioPress C2070 Troubleshooting Manual

1.1.3. Color spots (black spots)

(1) Symptom
Color spots (black spots) occurs
Yellow soft clumping
Yelllow soft cakeing
For human eyes, all looks like black spots on the print.
(2) Cause
When the temperature is high or the internal temperature increases too much, the toner or
carrier forms core. Around the core, transfer failure (1
appear.
How to classify the cause
Print test chart No53 with the density setting 255 and 128. See the sample through the loupe
with magnification x40 and look carefully the color spots.
For example, the cause of color spots on the magenta halftone could be attachment of carrier
of other color (Y/C/K) or toner (soft clumps). So please observe carefully.
In many cases, some of the above is mixed. So, take corrective action from the frequently
seen symptom.
•
For the carrier attachment, go to (Solution "1")
•
For the soft clumping, go to (Solution "2" or "3")
(3) Solution
1. Confirm that the color of the core then conduct following for the responding color.
1. Conduct Background margin fine adjustment.
Service mode→[Process Adjustment]→[Process Fine Adjustment]→[Background
Margin Fine Adj.] Change the setting to minus direction by 1 to 4 steps.
2. Utility/Counter →[Administrator Setting]→[System Setting]→[Expert
Adjustment]→[Process Adjustment]→[Front & Back Density]
Change the value by 1 to 2 steps to minus direction.
After changing the setting, conduct the Gamma Automatic Adjustment.
Service mode →[Process Adjustment]→[Drum Peculiarity Adjustment]]→[Gamma
Automatic Adjustment]
3. Check the maximum density and if it is different from target, conduct maximum
density adjustment.
Print 10 pcs of test chart No53 with the density setting 255 and 128, then see the
improvement level. (Confirm the variance of the occurrence.)
Note
•
Check that AC bias and AC frequency is set to "0".
•
After replacing developer to new one, print A3 with 15 % coverage by 100 sheets.
The lower the Duty, the better against the color spot. However it is
disadvantageous against the developing memory problem.
•
Front & Back adjustment is disadvantageous against white spots.
•
It is impossible to completely solve the soft clumping or carrier attachment issue.
However, if total 10 spots or over is seen in the entire A3 in solid or halftone, it can
KONICA MINOLTA Confidential
Magenta soft clumping
- 9 -
Black carrier
st nd
transfer/2 transfer) occurs and spots