Brother NX600 Service Manual page 205

Repair Manual
Problem Primary factors and causes
8 Stitch skipping, Bad needle interference
thread abrasion adjustment
Thread breakage
Loose needle interference
adjustment screw
Bad front-back needle drop
adjustment
Bad needle plate attachment
position
Bad needle bar rise adjustment
Loose timing adjustment screws Adjust needle
Stitch skipping, Bad needle bar height
thread abrasion adjustment
Thread breakage
Loose timing adjustment screws Adjust needle bar
9 Does not turn Bad main motor
(Electronic sounds
Main motor connector
and operating
disconnection
display lamps
Bad power supply unit F
normal at startup)
Bad SS-VR F PCB assy.
SS-VR F PCB assy. and
operation F3 PCB assy.
connector disconnected
Does not turn Bad NP PCB assy.
(No electronic
NP PCB assy. and main PCB
sounds / operating
assy. connector disconnected
display lamps
Bad pin jack assy.
normal at startup)
10 Irregular rotation Grease or dust adhering to
(rotation slow / fast speed sensor
/ unstable)
Grease or dust adhering to NP
PCB assy.
Bad NP PCB assy.
Interference between speed
sensor and NP PCB assy.
• Damage to speed sensor
• NP PCB assy. damage
Bad main PCB assy.
Repair method
Adjust needle interference(4-12)
Adjust needle interference(4-12)
Adjust needle interference(4-12)
Adjust left-right needle
interference
Reattach the needle plate
Adjust needle bar rise(4-8)
interference(4-12)
Adjust needle bar height(4-9)
height(4-9)
Replace main motor(3-27)
Plug connector in
Replace power supply unit F(3-
29)
Replace SS-VR F PCB assy. (3-
35)
Plug connector in
Replace NP PCB assy.(3-25)
Plug connector in
Replace pin jack assy.(2-10)
Remove grease or dust
Remove grease or dust
Replace NP PCB assy.(3-25)
Eliminate cause of interference
• Replace upper shaft
assy.(3-5)
• Replace NP PCB assy.(3-
25)
Replace main PCB assy. (3-25)
Items for Inspection method
Inspection and standards
Needle and tip Lightly press the lower
gap part (cover part) of the
SS button while running
on the right base line,
and check for the faint
sound of the needle
and tip hitting.
Back-front needle Turn the pulley by
drop position hand, and confirm that
there is a gap with the
needle before and after
the needle plate A
needle hole.
Needle bar rise With a 2.9 – 3.3 mm
rise from the lowest
Needle
point for the needle,
interference
confirm that the tip of
the rotary hook comes
to the left side of the
needle.(4-8)(make
reference mark on
needle bar supporter
assy. )
Needle bar When the needle and
height outside of the bobbin
tip meet when turning
the pulley on the left
base line, confirm that
the distance from the
top of the needle hole
to the bottom of the
rotary hook tip is 1.0 –
1.4 mm. (4-9)
Sewing machine Check that the sewing
runs when S/S machine starts and
button is pushed stops when the S/S
button is pushed when
green.
Machine Check that it switches
operation while to fast, middle and slow
rotating speed when the speed
control lever is
operated and that at
high speed there is no
rotational variation.
(4-12)
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