HP Designjet 4000 Printer series - Manual (Page 179)

If you have vertical misalignment, you will see something like this:
If you have bidirectional misalignment, you will see something like this:
Corrective action
1.
Align the printheads, using the same paper type with which you were
experiencing unacceptable print quality, if feasible (some paper types are not
suitable for printhead alignment). See “How do I align the printheads?” on page 119.
2. If there is no improvement in print quality, contact your customer service
representative.
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How do
I
use the
Image
Diagnostics
Print?