Brother DP-550CJ, Service Manual

Page: 169 / 194

REPAIR
Mechanical
SERVICE MANUAL
4-54
(8) Check the carriage motor "jumping" phase:
a) With the CR test still active, press the UP arrow key to turn the motor on.
b) Step the motor right with the RIGHT arrow key until the carriage moves to the
rightmost position and then "jumps" (moves) back to the left one step.
c) Verify that the motor phase at the "jumping" point is "CD", "D", or "DA" only.
d) If the motor phase is not correct, repeat steps (3) through (7) above, and
repeat this step (8) to verify that the motor "jumping" phase is still correct.
e) Press RETURN or CANCEL to end the Self Test, turn OFF the machine, and
reinstall the printer and all covers.
5.4.2. Adjusting Belt Tension
Belt tension is maintained by the pulley holder spring. The spring is preset to hold the
idle pulley in position to maintain the proper tension on the timing belt. If the carriage
does not move freely, or if the belt is removed or replaced, the tension should be
checked and adjusted as follows:
(1) With power disconnected from the machine, move the carriage to the left end
(maintenance station side) and verify that the belt is properly installed.
(2) Push the idle pulley holder to verify that it moves freely. If the pulley holder cannot
be moved smoothly, there is too much friction between the pulley holder and the
CA frame.
(3) Line up the carriage with the first star wheel from the left side of the CA unit
(maintenance station side), and engage a friction meter (push-pull gauge) on the
carriage at the belt holding portion.
(4) With the friction meter (push-pull gauge), pull the carriage to the right to the last
star wheel and verify that the carriage moves freely with a friction reading of less
than 0.7 kg force.
(5) If the carriage friction is not correct, loosen the idle pulley holder screw, move the
holder as necessary to change the tension on the pulley holder spring, and
retighten the screw.