Work Clamp Is Not Raised - Brother HE-800A Service Manual

5-24. Work clamp is not raised (2) Pulse motor stepping sound can be heard
Cause
Machine stopping
position
Work clamp lifting
speed is too fast.
Upper thread
scissors
Lower thread trimmer
Loose screws
Work clamp lifting
height setting
Threading
Check
Rotary hook touches
lower thread retainer at
the stop position
Work clamp lifting speed
setting
Interference between
upper thread scissors and
work clamp
Upper thread scissors
operation
Interference between
fixed knife set, lower
thread clamp, lower
thread presser and lower
thread retainer.
Rubbish, dust or thread
scraps present
Check for loose screws in
the upper thread trimmer,
lower thread trimmer and
work clamp lifter
mechanisms.
Check the work clamp
lifting height setting.
Lower thread threading
Lower thread tension
Remedy
Adjust the needle up stop position.
Retainer
Use memory switch No. 02 to retard the work clamp
lifting speed.
Check the standard adjustments with the upper
thread scissors removed.
* Be particularly careful when sewing joints.
Apply grease to the inclined face of the opening
cam.
Repair or replace the parts.
Lower thread
trimmer link A assembly
Remove all rubbish, dust and thread scraps from the
lower thread trimmer.
Securely tighten all screws.
Change the settings of memory switch Nos. 04, 05,
06.
* If the work clamp lifting height is too high, the lower
thread trimming operation will not be timed
together with the work clamp rising and the pulse
motor may go out of step.
Insert the bobbin correctly and pass the lower thread
through the bobbin case correctly.
* If the bobbin is inserted back-to-front, it will spin
loosely and the presser lifter may go out of step.
Reduce the lower thread tension.
* If the lower thread tension is too strong, the motor
may go out of step.
Use memory switch No. 02 to reduce the work
clamp lifting speed setting to make the lifting speed
slower.
Buff this section to reduce the
thread retaining resistance.
HE-800A
5. TROUBLESHOOTING
Inner rotary
hook presser
4021Q
Lower thread
trimmer
connecting rod
Remove the shoulder
screw to check.
4022Q
4023Q
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