Intermec EasyCoder PD4 Installation Instructions page 2

To install the thermal printhead
1 Turn off the printer and unplug the power cord.
2 Open the side door of the printer.
3 Raise the printhead by pulling out the printhead lever and turning it
counterclockwise a quarter of a turn.
4 Remove any thermal transfer ribbon.
5 Remove the old printhead by pulling it out toward the front of the
printer.
Steps 6-9 describe how to replace the printhead adapter PCB which is
necessary if you are changing to a printhead with different resolution (for
instance, going from 200 dpi to 300 dpi). If this is not the case, go to
Step 11.
Note: If you are using a PD4 printer, you cannot switch to a
printhead with a different resolution other than that which the
printer was designed for.