Brother NX600 Service Manual page 211

Repair Manual
Problem Primary factors and causes
18 Cannot sew BH BH sewing impossible
• BH is blocked
• Bad BH connecting point
• BH cannot
switch
• BH lever detached
• BH switches
• Connector disconnected
part way
through
• Operation drags
• BH presser button
attachment holder is pulled
out fully.
Becomes straight Bad feed forward/reverse
line adjustment (100 stitches forward
and reverse)
19 Cut thread switch Bad operation PCB assembly
is pushed but there
is no thread cutting
Bad SS-VR F PCB assy.
operation
Bad main PCB assy.
Bad thread cutter pulse motor
Thread cutter pulse motor
connector disconnected
Parts related to the thread cutter
lever gear drag
Thread cutter Thread scraps and dirt adhering
operates, but the to the thread hook assy.
thread is not cut
Bad timing for thread hook
assembly fly out.
• Grease or dust adhering to
NP sensor
• Bad NP PCB assy.
• NP PCB assy. connector
disconnected
• Interference between NP
sensor and NP PCB assy.
Thread hook assy. does not grab
the thread.
• Bad thread hook assy.
shape
• Thread hook lever presser
spring floating
• Lack of inner rotary hook
pile
Bad cutting edge on NT lower
thread cutter.
Repair method
Readjust BH switch
(4-19)
Replace BH switch assy.(3-59)
Plug connector in
Replace BH switch assy.(3-59)
Reset the range for the BH
presser button attachment
(Move back two marks from the
maximum permissible range)
Adjust feed forward/reverse(4-
17)
Replace operation PCB
assembly(3-37)
Replace SS-VR F PCB assy. (3-
35)
Replace main PCB assy. (3-25)
Replace C pulse motor (3-75)
Plug connector in
Reassemble the parts for which
operations drag
Remove thread scraps and dirt
Remove grease or dust
Replace NP PCB assy.(3-25)
Plug connector in
Eliminate cause of interference
Replace NP PCB assy.(3-25)
Replace thread hook assy. (3-
77)
Replace presser spring(3-77)
Replace inner rotary hook
Replace NT lower thread cutter
(3-77)
Items for Inspection method
Inspection and standards
Bar-tack Check that there is no
Eyelet sewing stitch skipping or
clogging with BH
pattern sewing.
With the BH presser
moved the extent of its
range by hand, confirm
that there is slack on
the BH side and the
other side. (4-19)
Thread cutting Carry out thread cutting
function on the left base line and
the right base line, and
confirm that the
Schappe Spun Sewing
Thread #60 is actually
cut. (3-77)
6 - 9