Baby Lock PRO BL8800 User manual

MODEL BL8800
SERVICE MANUAL

- 1 -
TABLE OF CONTENTS
A.REMOVING THE FRONT COVER............................. 2
B. REPLACING THE FRONT COVER........................... 4
1. HEIGHT OF NEEDLE BAR........................................ 5
2. GAP BETWEEN NEEDLE AND HOOK ..................... 6
3. TIMING OF THE HOOK............................................. 7
4. HEIGHT OF THE FEED DOG.................................... 8
5. NEEDLE PLATE AND NEEDLE POSITON ............... 8
6. TIMING OF THE FEED MOTION .............................. 9
7. ADJUSTING THE FORWARD AND REVERSE
STITCH ................................................................. 10
8. BOBBIN WINDER .................................................... 10
9. HEIGHT AND DIRECTION OF PRESSER FOOT ... 11
10. HEIGHT OF NEEDLE THREADER ....................... 11
11. ZIGZAG TIMING • NEEDLE STOP POSITION ..... 12
12. MOTOR BELT TENSION....................................... 12
13. TIMING BELT TENSION........................................ 12
14. BACKLASH OF HOOK GEAR ............................... 13
15. UPPER THREAD TENSION UNIT......................... 13
16. ADJUSTING THE LOWER THREAD TENSION.... 13
LOCATING THE DEFFECTED ELECTRICAL PART .. 14
The self-diagnostic program......................................... 14
HOW TO CHECK......................................................... 14
a. Frequency of power line........................................... 14
b. Condition of switches and sensors .......................... 15
b-1. Adjustment for buttonhole lever position............... 16
c. Phase of feed pulse motor ....................................... 17
d. Phase of zigzag pulse motor.................................... 17
e. Condition of foot controller and speed control lever. 17
WARNING MESSAGES ON LCD ................................ 17
TROUBLE SHOOTING OF ELECTRICAL PARTS...... 18

a
b
c
fig. A-1
fig. A-2
fig. A-3
fig. A-4
d
fig. A-5
e
- 2 -
A.REMOVINGTHE FRONT COVER
1. Remove the set screw (a) and the light cover. (fig. A-1)
2. Remove the left side screw (b) inside the thread take
up lever cover. (fig. A-2)
3. Remove the screw (c) located on the backside of
machine, above the spool pin. (fig. A-3)
4. Tilt the machine backward.
Remove the 4 screws (d) and base. (fig. A-4)
5. Remove the 2 screws (e) on the bottom of front cover.
(fig. A-5)

f
fig A-6
fig A-7
g
fig A-8
h
ij
fig A-9
- 3 -
6. Stand up the machine.
The terminal cover will come out.
Insert the screwdriver into the hole of machine from
backside.
Hook the tip of driver into the groove of forward-
reverse adjusting knob (f). (fig A-6)
Slide them to the left and remove the knob.
7. Hook the tip of screwdriver to the front cover holder (g)
and pull down. (fig. A-7)
8. Tilt the machine backward again.
Hold the machine casting and push the left bottom
corner (h) of front cover upward. The hook inside of the
cover will come off. (fig. A-8)
9. Bring up the front cover carefully.
Disconnect the two cord connectors (i, j) from the CPU
curcuit board. (fig. A-9)
Terminal
cover

fig. B-1
fig. B-2
fig. B-3
fig. B-4
k
l
n
m
m
n
fig. B-5
f
- 4 -
B. REPLACINGTHE FRONT
COVER
1. Lower the presser foot lifter (k).
Turn the hand wheel toward you until the thread take-
up lever (l) rises to its highest point. (fig. B-1)
2. Connect the two cord connectors (i, j) from front cover
to the CPU circuit board on machine. (fig. A-9)
3. Set the front cover onto the machine casting so that
the tip of thread tension relasing lever (m) should be
hooked into the notch of tension guide (n). (fig. B-
2,3,4)
Check that the tension releasing mechanism has been
connected certainly.
4. Press the left side of front cover downward so that the
hook inside of cover will snap into a place.
5 Tighten the 2 screws (e) onto the bottom of front cover.
(fig. A-5)
6. Push up the front cover holder (g). (fig. A-7)
7. Insert the forward-reverse adjusting knob (f) into the
hole with the hook facing forward. (fig. B-5)
8. Replace the terminal cover and base, and tighten 4
screws (d) onto the base. (fig. A-4)
9. Tighten the screw (c) onto the back of machine. (fig. A-
3)
10.Tighten the screw (b) onto the take-up lever cover. (fig.
A-2)
11. Replace the light cover and screw (a). (fig. A-1)

fig. 1-1
fig. 1-2
fig. 1-3
a
5.2±0.2 mm
b
- 5 -
1. HEIGHT OF NEEDLE BAR
Height of needle bar could be the cause for stitches to
skip. Check as the following procedures.
1. Set the pattern number at “2” which is straight stitch on
center needle position.
2. Raise the needle bar to its highest point by turning the
handwheel toward you. Remove the presser foot.
Remove the set screw (a) and needle plate. Lift up the
bobbin holder and remove it. (fig. 1-1)
3. Turn the handwheel toward you until the needle comes
to its lowest point.
Then, the spacing between the surface of hook race
and the top edge of needle eye must be 5.2±0.2 mm.
(fig. 1-2)
(= Turn the handwheel until the top edge of needle eye
is aligned with the surface of hook race, at this time the
needle bar should be rising 5.2±0.2 mm from its lowest
point.)
If this spacing is not correct, adjust as follows.
4. Remove the light cover.
5. Lower the needle to its lowest point by turning the
handwheel.
6. Loosen (not remove) the screw (b) on the needle bar
holder. (fig. 1-3)
Raise the needle bar until the needle eye is aligned
with the hook race. Then, lower the needle bar 5.2 mm
and re-tighten the screw (b).
CAUTION: DO NOT change the needle bar direction at
this adjustment. The long groove of needle must be
facing frontwards.

fig. 2-1
fig. 2-2
0.02-0.1 mm
fig. 2-3
fig. 2-4
a
- 6 -
2. GAP BETWEEN NEEDLE AND
HOOK
If the needle hits aginst the hook, it may be the cause of
needle and thread breakages. If the gap between needle
and hook is too big, it will cause to skip stitches. Check
and adjust as follows:
Prior to make this adjustment, check that the needle is not
bent and the needle is inserted correctly.
1. Remove the needle plate and bobbin holder. (See Sec.
1-2)
2. Set the pattern number at “1” . (Straight stitch on left
needle position)
3. Turn the handwheel toward you until the needle will
cross over the hook. (fig 2-1)
Then, check the gap between needle and hook is
about 0.02 to 0.1 mm. (fig. 2-2)
If the needle is hitting against the hook or if the gap is too
much, adjust as follows:
4. Remove the light cover.
5. Remove the cap on the back side of machine. (fig. 2-3)
6. Loosen (do not remove) the lock screw with a hexagon
socket screw key (3 mm). (fig.2-4)
Adjust the gap by turning the adjusting nut (a) with an
open ended spanner (10 mm).
- If the gap is too big, turn the nut upward.
- If the needle is hitting the hook, turn the nut
downward.
When correct gap is obtained, hold the nut and
retighten the lock screw. Check the gap again.
7. Replace the cap and light cover. Replace the bobbin
holder and needle plate.

fig. 3-1
fig. 3-2
a
fig. 3-3
b
fig. 3-4
1.5-2.0 mm
- 7 -
3.TIMING OFTHE HOOK
Prior to making this adjustmetnt, be sure that the needle
bar is set at the correct height. (See sec. 1)
Check the timing of hook as follows:
1. Remove the needle plate and bobbin holder. (See sec.
1-2)
2. Set the pattern number at “1”. (Straight stitch on left
needle position)
3. Turn the handwheel toward you until the needle is at
its lowest point.
4. Then, turn the handwheel slowly to turn the hook
counter-clockwise until the tip of hook is aligned with
the right side of needle. (fig. 3-1)
At this time, the gap between the tip of hook and the
top edge of needle eye should be 1.5 to 2.0 mm.
If the gap is too small or too large, adjust as follows:
5. Tilt the machine backward.
Remove the bed lid by removing the screw (a) and
sliding bed lid to the left. (fig. 3-2)
6. Loosen the two screws (b) on the lower shaft gear with
a hexagon socket screw key (2.5 mm). (fig. 3-3)
7. Turn the hook race by hand so that the tip of hook will
align with the right side of needle.
In this position, hold the race with your left hand and
turn the handwheel toward you to obtain the correct
gap (1.5 to 2.0 mm). (fig. 3-4)
8. Tighten the screws (b) and check the timing again.
9. Replace the bed lid, bobbin holder and needle plate.

fig. 4-1
fig. 4-2
0.8+0.05 mm
-0
ab
fig. 5-1
fig. 5-2
a
- 8 -
4. HEIGHT OFTHE FEED DOG
If the feed dog does not come up over the needle plate
enough, it will result in insufficient and/or uneven feed of
fabrics.
The feed dog should come up over the needle plate
0.8+0.05 -0 mm. (fig. 4-1)
If it does not come up enough, adjust as follows:
1. Tilt the machine backward and remove the bed lid by
removing the screw and sliding it to the left. (See sec.
3-5)
2. Lower the presser foot lifter. Turn the handwheel until
the feed dog comes to its highest position.
3. Loosen the lock nut (a). Adjust the height of the feed
dog correctly by turning the inner screw (b). (fig. 4-2)
4. Hold the screw (b) and re-tighten the lock nut (a).
5. Re-check the height and motion of feed dog by turning
the handwheel.
5. NEEDLE PLATE AND NEEDLE
POSITON
When the zigzag width is set at maximum, the needle
should fall evenly into the both sides of needle plate hole (
the distance needle and edge of hole at each side). (fig.
5-1) If it is not so, adjust as follows:
1. Set the pattern number at “4” and stitch width to 5.
2. Remove the presser foot and the light cover.
3. Loosen the screw (a) located on the top of the needle
bar guide assembly. (fig. 5-2)
By slightly moving the needle bar left or right, adjust
the needle position so that the needle falls evenly into
the hole.
4. Tighten the screw (a) and re-check the position of
needle.

fig. 6-1
a
fig. 6-2
fig. 6-3
b
- 9 -
6.TIMING OFTHE FEED MOTION
If the feed motion is too fast of foo slow, it will be the
cause of fabfic puckers or needle breakage. Check and
adjust the feed timing as follows:
1. Tilt the machine backward and remove the bed lid by
removing the screw and sliding it to the left. (sec. 3-5)
2. Check that the guide-lines on the lower shaft and feed
cam should be aligned. (fig. 6-1)
If it is not so, adjust as follows.
3. Loosen the two screws (a) on the feed cam with a
hexagon socket screw key (2 mm).
Hold the feed cam with a screw key and turn the
handwheel either direction until the guide lines on the
lower shaft and feed cam are aligned.
4. Tighten the screws (a).
Next, check the timing of the up-down movements.
5. Turn the handwheel toward you until the needle comes
to its lowest position.
At this time, the guide-line on the feed rock cam should
be coming to its lowest point. (fig. 6-2)
If not, adjust as follows:
6. Remove the base.
Loosen the two screws (b) on the belt pulley with a
hexagon socket screw key (2 mm). (fig. 6-3)
7. Turn the lower shaft so that the guide line comes to its
lowest point.
At this point, hold the lower shaft with a pair of pincers
not to retate and turn the handwheel until the needle
comes to its lowest position.
8. Tighten the two screws (b).
9. When you have adjusted the timing of up-down
movement, check the timing of hook again. (sec. 3)
Guide Line
Guide Line