HP Designjet 4000 Printer series - Manual (Page 113)

3. Push down as indicated by the arrow shown below.
When installing the new printhead there may be some resistance, so you need to
press it down firmly but smoothly.
If you have difficulty, see “The problem is I cannot insert a printhead” on page 207.
4. Insert any other printheads that need to be installed, and close the carriage cover.
When all the printheads have been inserted correctly and accepted by the printer,
the printer will beep.
Note If the printer does not beep when you insert the printhead and the
Replace message appears on the front panel, the printhead may need to
be reseated.
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How do
I
handle
the
ink
system?