Intermec EasyCoder 501 XP Service Manual page 45

Chapter 8 Print Unit
8.3 Stepper Motor
44
Description
The stepper motor drives the platen roller via a short belt and the
ribbon assist roller and the ribbon rewind unit via another, longer
belt. A freely rotating pulley attached to the printer's center section
makes the outside of the longer belt drive the ribbon assist roller.
The stepper motor is driven in half-step mode between 70 and
145 mm/sec., and in full-step mode between 145 and 300 mm/sec.
However, when motor slows down at the end of a label, it will still
be driven in full-step mode even below 145 mm/sec., which will
result in a slightly increased noise level during the last centimetre
or so of the label.
The stepper motor has a stop accuracy of 2 dots, that is the theoreti-
cal feed error will be max. +1 dot. However, mechanical condi-
tions such as a worn platen roller or a slippery liner may affect the
feed accuracy adversely.
The stepper motor is fi tted by means of two #T20 Torx screws to a
bracket, which in its turn is attached to the print unit gable by three
#T20 Torx screws. The pulleys of the stepper motor are glued to
the motor's shaft.
Replacement
Replace the stepper motor as follows:
• Switch off the power and disconnect the power cord.
• Open the front and right hand doors.
• Remove the cover over the electronics compartment, which is
held by eight #T10 Torx screws.
• Disconnect the cable to the stepper motor from P420 on the
CPU board.
• Remove the tension of the belt to the ribbon rewind unit by
loosening the two #T20 screws that holds the unit.
• Dismantle the stepper motor from the bracket by removing the
two #T20 Torx screws.
• Free the belt from the pulley of the ribbon rewind unit and
manipulate the stepper motor so it comes free from both belts.
Remove the stepper motor.
• When putting back the stepper motor, fi t the short belt fi rst,
while letting the long belt hang loosely on the idler in a loop,
through which you can insert the pulley of the stepper motor.
Do not put the long belt around the pulley of the ribbon rewind
unit until you have fi tted the stepper motor to the bracket and
checked that both belts are engaged by the pulleys.
• Connect the cable of the stepper motor to P420 on the CPU
board (marked "STM1".)
• Adjust the tension of the belts as described in Chapter 8.5 and
put back the cover.
Refer to illustration on next page!
Intermec EasyCoder 501 XP – Service Manual Ed. 4