Baby Lock BL7800, Service Manual

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∗
You must turn off the power and remove the connectors from printed circuit boards before measuring resistance.
∗
Refer to the illustrations for check locations.
PROBLEM CHECK REMEDY
1.
When power is
turned on, buzzer
does not sound and
the LED does not
light up.
1)
If the voltage between both inlet terminals is
measured when the power cord is plugged in
is the standard voltage (120 VAC, 220V,
230V, 240V) displayed.
2)
When power switch is set to on, is resistance
at both ends less than 1
Ω
?
3)
Remove connector CN2 from the power
supply board, and check following voltages
using a tester:
Voltage between pins 2 and 3 should be
about DC 5V. Voltage between pins 4 and 5
should be DC 20 to 30 V.
4)
Is the fuse blown?
5)
Other
1)
Replace the power cord.
2)
Replace the power supply unit
assembly.
3)
Replace the power supply unit
assembly.
4)
Replace the fuse after correcting
defect that caused fuse to blow.
5)
Replace the main PC board
assembly or operation board
assembly.
2.
After the power is
turned on, pulse
motors do not
return to their home
positions with
respect to the
needle position.
(Zigzag pulse motor
when needle bar is
raised and feed
pulse motor when
needle bar is
lowered.)
1)
Are the resistances between the connector
pins given below normal for pulse motors
which do not return to the home position?
Zigzag (CN1).................. 1-3, 2-4
→
8 to 10
Ω
Feed (CN2).................. 1-3, 2-4
→
8 to 10
Ω
2)
Set the home position for the same pulse
motors irrespective of needle position.
3)
Is a fuse blown?
4)
Is the voltage between pins 4-5 normal when
the connector (CN9) which is output from the
power supply board is disconnected?
Between 4-5 DC 20 - 30 V
5)
Others
1)
Replace the pulse motor which
shows an abnormality, or the
lead wire assembly.
2)
Replace the NP PC board
assembly.
3)
Replace the fuse after correcting
the defect that caused the fuse
to blow.
4)
Replace the power supply unit
assembly.
5)
Replace the main PC board
assembly.
3.
Pattern cannot be
selected.
1)
Does switch on SS PC board remain in the
pressed condition after the key on the
operation board is pressed?
2)
When the foot controller is connected, does it
remain depressed?
3)
Others
1)
Adjust installation, or replace the
SS PC board assembly or
operation board.
2)
Check.
3)
Replace the operation board
assembly or main PC board
assembly.
4.
Main motor does
not run.
1)
Does the balance wheel rotate easily?
2)
Is main motor connector (CN2 on power
supply unit) connected properly?
3)
Is resistance of both ends of main motor
connector (CN2 on power supply unit) 24 to
34
Ω
?
4)
Do start/stop switch, backstitch switch, needle
position switch, and thread cutter switch
operate correctly?
Resistance at both ends of each switch:
When switch is pressed .......... 1
Ω
or less
.
When switch is released
.........
∞
1)
Adjust the installation position so
that it moves easily.
2)
Check
3)
Replace the main motor.
4)
Replace the SS PC assembly.