Brother BES-1240BC Instruction Manual page 263

Symptom
Thread is frequently tangled in the
rotary hook.
The lower shaft motor zero point er-
ror occurs.
The lower shaft motor standby posi-
tion error occurs.
The lower shaft overheat error oc-
curs.
• Is thread tangled in the rotary hook?
Clean the rotary hook.
• Conduct BC sensor test of the test mode.
If there is any failure, replace the lower shaft module with a new
one.
• Conduct automatic out-of-step limit measurement of BC automatic test
in the test mode.
Replace the lower shaft module with a new one if there is any fault.
• Check to see if the lower shaft fan of the head with which the error
frequently occurs is correctly rotating.
If the fan is at standstill, check to see if connection from the lower
shaft fan to the BC PCB is proper. Replace the lower shaft fan with a
new one.
• If all the lower shaft fans are at standstill, check fuse F4 on the power
supply PCB in the control box.
• Is the hole next to the bed with which the error frequently occurs clogged
with dust?
If so, clean it.
• Is thread tangled in the rotary hook?
Clean the rotary hook.
• Is the lower shaft with which the error occurs rotating?
If so, check to see if connection from the lower shaft sensor PCB to
the BC PCB is proper. Adjust the lower shaft sensor. Replace the
lower shaft sensor PCB with a new one.
• If the lower shaft with which the error occurs is not rotating, check to
see if connection from the lower shaft motor to the BC PCB is proper.
Replace the lower shaft module with a new one. Replace the BC PCB
with a new one.
• Is the rotary hook rotated manually?
This is not a fault.
• Check to see if connection from the lower shaft sensor PCB to the BC
PCB is proper. Replace the lower shaft module with a new one.
• Check to see if the lower shaft fan is normally rotating. If the fan is at
standstill, check to see if connection from the lower shaft fan to the BC
PCB is proper. Replace the lower shaft fan with a new one.
• If all the lower shaft fans are at standstill, check fuse F4 on the power
supply PCB in the control box.
• Is the hole next to the bed with which the error frequently occurs clogged
with dust?
If so, clean it.
• Check to see if connection from the thermister of the lower shaft module
to the BC PCB is proper.
BES-940BC • BES-1240BC
Chapter 12 Trouble Shooting
Measures
261