Canon S820MG Service Manual page 203

With GP301/HG-201 media, uneven
print density due to carriage
imbalance appears as vertical lines
in the print.
If port settings are not ECP and a
large file is printed, the print speed is
extremely low.
(cf. A3100-ECPSpeed.XLS)
GP301 friction with head occurs
when "Highest Quality" is selected in
the driver's Custom setting.
In order to prevent printed sheets
rubbing against each other, feeding
pauses immediately before a sheet
is ejected on top of a still-wet high
density printout.
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All Vibration from the motor causes off-target dot
placement. As the off-target dot placement
always occurs at the same locations during
head alignment, it is considered uneven
vertical density.
All The data quantities sent are large. Because
of this, the difference in transfer speed
between ECP and other settings has a
marked effect on print speed.
All Due to 12 pass printing, print speed is low
and it becomes easy for cockling (buckling of
the paper) to occur.
All Specifications.
ManualsBooks
Intentionally raise alignment values by one
step after head alignment. By slightly shifting
the entire head alignment from the accurate
position, uneven vertical density becomes
unnoticeable.
[Method]
1. Perform head alignment from the driver
utility.
2. Perform the head alignment again.
3. Intentionally select one value higher for
pattern E.
[Note]
Although uneven vertical density will
disappear, there may be horizontal striping
and a noticeable loss of sharpness.
USB connection is recommended. In the
case of parallel connections, change port
settings to ECP.
Adjust the paper thickness lever setting when
the problem occurs
[Note]
The message "The paper thickness lever is
not set correctly" will appear.
Change the driver settings.
[Method]
1. In the driver utility, while pressing down the
shift key, select "Custom Settings."
2. Uncheck the option "Prevent inter-sheet ink
transfer."
[Note]
When the setting above is turned off, ink
smearing due to friction between output
pages is likely to occur.