HP Designjet 4000 Printer series - Manual (Page 237)

Tell me about printheads
In order to increase printing speed, two printheads are connected to each ink
cartridge, giving eight printheads in total.
The printheads are extremely durable and do not need to be replaced every time an
ink cartridge is replaced. They will continue giving excellent results even if the ink
cartridges are low in ink.
To maintain optimum print quality, the printheads are automatically tested at regular
intervals, and automatically serviced if necessary. This takes a little time and will
occasionally delay printing.
When a printhead eventually needs to be replaced, the front panel identifies the
printhead with a cross in place of the printhead number:
Caution Whenever you buy a new printhead, you get a new printhead
cleaner with it. When you replace a printhead, always replace the printhead
cleaner at the same time. Leaving the old printhead cleaner in the printer will
shorten the new printhead's life and possibly damage the printer.
235
Tell me about
the ink
system