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a

 fig. 12

a

 fig. 13

a

- 12 -

11. ZIGZAG TIMING • NEEDLE

STOP POSITION

The zigzag timing and the needle stop position when
start/stop switch is pressed are controlled by the
computer system. However, the needle bar position
(upper shaft revolution angle) is detected by the sensor
slit.
Therefore, if the slit is not correct position, the timing and
stop position will be incorrect. Adjust as follows:

1. Remove the front cover.

2. Loosen the screw (a) on the timing slit with a hexagon

socket screw key (1.5 mm). (fig. 11)
Align the guide-lines on the upper shaft and left side of
slit.
At this adjustment, do not move the slit side-ways.

3. Tighten the screw (a).

12. MOTOR BELT TENSION

If the motor belt tension is too tight or too loose, machine
will not run smoothly.
Adjust as follows:

1. Remove the front cover.

2. Loosen the screw (a). (fig. 12)

3. Push the pulley towards the belt so that the belt should

have flexibility of 5-6 mm when average pressure is
applied on its side.

4. Tighten the screw (a).

13. TIMING  BELT TENSION

If the timing belt is too tight or too loose, the machine will
run heavily or the timing of hook and feed motion will be
changed incorrectly.
Adjust as follows:

1. Remove the front cover.

2. Loosen the screw (a). (fig. 13)

3. Push the pulley towards the belt and tighten screw.

The belt tension should have a flexibility of 4-5 mm
when average pressure is applied to its side.

When you have adjusted the timing belt tension, recheck
the timing of the feed motion (sec. 6) and the timing of the
hook (sec. 3 ) again.

 fig. 11 View from lowerside

Summary of Contents for PRO BL8800

Page 1: ...MODEL BL8800 SERVICE MANUAL...

Page 2: ...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 LOCA...

Page 3: ...e 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 machin...

Page 4: ...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...

Page 5: ...ension 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...

Page 6: ...cing 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 tim...

Page 7: ...d 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 a...

Page 8: ...t 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 b...

Page 9: ...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...

Page 10: ...l 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...

Page 11: ...the screw d fig 7 3 If the forward stitch is finer than the reverse stitch turn the screw to the right fig 7 2 b If the reverse stitch is finer than the forward stitch turn the screw to the left fig...

Page 12: ...er foot lifter has a slight play in down position 10 HEIGHT OF NEEDLE THREADER If the height of needle threader is not correct the hook on therader will not enter the needle eye Adjsut as follows 1 Re...

Page 13: ...N If the motor belt tension is too tight or too loose machine will not run smoothly Adjust as follows 1 Remove the front cover 2 Loosen the screw a fig 12 3 Push the pulley towards the belt so that th...

Page 14: ...ou have adjusted the backlash of hook gear check the timing of the hook again sec 3 15 UPPER THREAD TENSION UNIT The upper thread tension regulator unit has been adjusted to the best sewing conditions...

Page 15: ...ch fig I 3 When this program has started correctly the LCD will indicate the machine icon and version number of this program fig I When buttons are released the LCD will change to indicate the Frequen...

Page 16: ...dle bar position 1 not intercepted 0 intercepted left needle position This sensor is intercepted by the lever of gear on the zigzag pulse motor shaft Move the needle bar right or left and check the re...

Page 17: ...ile lifting the presser foot lifter slightly Then slowly move frame back again Lower the lifter when BH f changes to 0 5 At this time the presser foot frame should be about 1 mm forward from the extre...

Page 18: ...f foot controller and speed control lever The condition of foot controller is indicated on the first line of LCD Foot controller is not connected the number 255 will appear Connect the foot controller...

Page 19: ...ser foot is lifted Check the Presser foot switch by Self diagnostic program Exchange the Presser foot switch Exchange the CPU circuit board Bobbin wind icon is appeared although the Bobbin winder spin...

Page 20: ...rcuit board LCD does not indicate Exchange the LCD board Exchange the CPU circuit board Can not control sewing speed by Speed control lever Check the condition of the Speed control lever by Self diagn...

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