Baby Lock BL7800, Service Manual

Page: 42 / 46

- 40 -
9.
Vertical movement
of the needle bar
and backstitch
operation are
abnormal.
1)
Are the resistances of both ends of each
switch on the SS PC board either 1
Ω
or less
or
∞
depending on whether the switch is on or
off?
2)
Do the voltages between pins 2-1, 4-1, 5-1,
and 6-1 of the NP PC board assembly
connector (CN3) alternate between DC 0 to 5
V when the machine is operated slowly?
3)
Is the bobbin winder switch turned off?
4) Others
1)
Replace the SS PC board
assembly.
2)
Replace the NP PC board
assembly.
3)
Adjust the bobbin winder
mechanism (see page 31).
4)
Replace the main PC board
assembly.
10.
Foot controller does
not operate
normally when
depressed.
1)
Is the resistance between 2-3 of the pin jack
connector (CN11) 1
Ω
or less when there is
no pin jack and when there is a pin jack?
2)
Does the resistance between 1-3 of the pin
jack connector (CN11) change from the low
Ω
range to 10k
Ω
when there is a pin jack and
the foot controller is depressed?
3)
Others
1)
Replace the jack assembly.
2)
Replace the foot controller or
jack assembly.
3)
Replace the main PC board
assembly.
11.
Thread tension can
not be set well.
1)
Is the thread route correct?
2)
Is the insertion of the lower thread correct?
3)
Is the combination of needle, fabric, and
thread correct?
4)
Is the dial tension correct?
5)
Is the rotary hook tension correct?
6)
Is the gap in the thread tension device
correct?
1)
Check
2)
Check
3)
Check (see page 36)
4)
Adjust the dial tension and upper
thread tension (see page 32).
5)
Adjust the rotary hook tension
(see page 33).
6)
Adjust the upper thread tension
(see page 32).
12.
Needle bar release
mechanism does
not operate
correctly.
1)
Does the needle bar release mechanism
operate smoothly?
2)
Is resistance between 1-3 and 2-4 of the
zigzag pulse motor connector CN1 8 to 10
Ω
?
3) Others
1)
Adjust the needle bar release
mechanism.
2)
Replace the zigzag pulse motor
or the ZPM lead wire assembly.
3)
Replace the main PC board
assembly.
13.
Thread cutting does
not operate
normally.
1)
Does it move easily?
2)
Is resistance between 1-3 and 2-4 of the feed
pulse motor connector CN3 8 to 10
Ω
?
3)
Others
1)
Adjust the thread cutting device.
2)
Replace the feed pulse motor or
the FPM lead wire assembly.
3)
Replace the main PC board
assembly.
14.
LED does not light
up.
1)
Is the main connector for the main PC board
and operation board correctly set?
2) Others
1)
Check
2)
Replace the operation board or
the main PC board.
15.
Thread can not be
wound around the
bobbin.
1)
Is resistance between both ends of the
bobbin winder switch connector (CN10) under
1
Ω
when thread is wound, and
∞
in other
cases?
2)
Is the bobbin winder installed correctly?
3)
Others
1)
Replace the bobbin winder
switch assembly.
2)
Adjust (see p. 31).
3)
Replace the main PC board.