Operation Of Main Motor Is Not Stable, Maximum Speed Operation Is Not Possible, Or Speed Cannot Be Adjusted; Correct Patterns Are Not Created; Buttonholes Are Not Stitched Correctly; Manual Operation Of Feed And Zigzag Is Not Possible - Baby Lock BL7800 Service Manual

Main motor does
4.
not run.
Operation of main
5.
motor is not stable,
maximum speed
operation is not
possible, or speed
cannot be adjusted.
Correct patterns are
6.
not created.
Buttonholes are not
7.
stitched correctly.
Manual operation of
8.
feed and zigzag is
not possible.
Is the presser foot lever lowered, or does the
5)
presser foot switch operate correctly?
Resistance at both ends of switch:
When switch is pressed .......... 1
When switch is released .........
Others
6)
When turning on power and moving the
1)
speed slide, does voltage between pins 3-2 of
the speed VR connector change between DC
0 to 5 V?
When operating the machine at a slow speed,
2)
do voltages between pins 2-1, 4-1, 5-1, 6-1 of
connector CN3 of the NP PC board each
alternate between DC 0 to 5 V?
Others
3)
If the power is turned off and the needle bar is
1)
moved horizontally by hand, does it move
easily?
Are the resistances between the connectors
2)
for the zigzag, feed, and side feed pulse
motors normal?
(CN1).................. 1-3, 2-4 → 8-10 Ω
Zigzag
(CN2).................. 1-3, 2-4 → 8-10 Ω
Feed
When operating the machine at a slow speed,
3)
do voltages between pins 2-1, 4-1, 5-1, 6-1 of
connector CN3 of the NP PC board each
alternate between DC 0 to 5 V?
Others
4)
Is the presser foot correct?
1)
Is the resistance between pins 4-5 of the BH
2)
switch connector (CN5) normal?
When buttonhole lever is lowered .... 1 Ω or less
When buttonhole lever is raised ......................∞
When the buttonhole lever is lowered and in
3)
the conditions below, is the resistance
between pins 1-2 and 2-3 of the BH switch
connector (CN5) normal?
Buttonhole lever is
pulled forward.................. 1 Ω or less
Buttonhole lever is
pushed back ....................
4) Others
The feed and zigzag manual keys turn off and
1)
on normally?
Does the voltage alternate between DC 0 to 5
2)
V at both ends of the main PC board
condensers C4 and C9 when the power is
turned on and the feed manual VR and zigzag
manual VR are slid?
Are the resistances normal between the pins
3)
of the feed and zigzag pulse motors listed
below?
(CN2).................. 1-3, 2-4 → 8-10 Ω
Feed
(CN1).................. 1-3, 2-4 → 8-10 Ω
Zigzag
4) Others
Ω
or less
∞
Between 1-2 Between 2-3
∞
∞ 1 Ω or less
- 39 -
Replace the presser foot SW
5)
assembly.
Replace the main PC board
6)
assembly or power unit
assembly.
Replace the VR PC board
1)
assembly.
Replace the NP PC board
2)
assembly.
Replace the main PC board.
3)
Adjust the installation position so
1)
that it moves easily.
Replace the malfunctioning
2)
pulse motor or the lead wire
assembly.
Replace the NP PC board
3)
assembly.
Replace the main PC board
4)
assembly.
Check
1)
Adjust or replace the BH switch
2)
assembly.
Adjust or replace the BH switch
3)
assembly (see page 30).
Replace the main PC board
4)
assembly.
Replace the operation board
1)
assembly.
Replace the operation board
2)
assembly.
Replace the feed or zigzag pulse
3)
motor, or the lead wire
assembly.
Others
4)