Canon imagePRESS C10000VPSeries Troubleshooting Manual page 59

[Attention] The density on a high density image may be lower when the secondary transfer voltage gets lower by changing this
setting.
If the symptom does not improve enough, change the setting of the secondary transfer voltage back to the original one , and then
go to the step 7).
7) Select "Adjust Gross/Fine Black" and press "Change".
[Reference] In case Adjust Gross/Fine Black will not be displayed on the control panel, change the setting value of Service Mode
> Mode List > COPIER > Option > DSPLY-SW > IMGC-ADJ to "1". The value is "0" by default.
8) Press "-" button for gloss, Make sure the setting value [a] is set to "-1" and press "OK".
The setting range is from "-4" to "+4" ("0" by default).
Change of the setting value changes the fixing temperature.
[Caution] Changing the value may cause glossiness of image may slightly decrease.
9) Output the image having shown the symptom, and check that the symptom does not occur.
If the symptom does not improve, then check other factors.
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