Canon imagePRESS C850 Series Troubleshooting Manual page 17

[Reference] In case Adjust Fixing Speed 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.
6) Change the setting value to minus side and press "OK" button.
The configurable range for the value is from "-20" to "+20". (Default: 0)
7) Select the paper type which is set from step 2) to step 6) and output the image which had the symptom to make sure that the
symptom does not occur any more.
If the symptom does not improve, then check other factors.
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