HP Designjet Z3100 Photo Printer series - Manual (Page 183)

First look at the upper part of the print (part 1). Each colored rectangle should be a uniform color without
any horizontal lines across it.
Then look at the bottom part of the print (part 2). For each individual colored pattern, check that most of
the dashes are present.
If you see horizontal lines in part 1 and also missing dashes in part 2 for the same color, the printhead
responsible needs cleaning. However, if the rectangles look solid, do not worry about just a few missing
dashes in part 2; these are acceptable because the printer can compensate for a few clogged nozzles.
Here is an example of a light gray printhead in a good state:
ENWW The Image Diagnostics Print 173
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