SERVICE MANUAL FOR B373 (STAR110, PS-2200)E B375 (STAR120E, PS-2300) B376 (STAR130E, PS-2400) B377 (STAR140E, PS-2500) 5. 1998.
GENERAL INFORMATION · · · This service manual is complied for repairing service of domestic sewing machines PS2200, 2300, 2400 , 2500, STAR 110, 120E, 130E and 140E. Use this manual with Parts Catalogue for fault findings when you make a repair. This machine is manufactured based on up-to-date product specifications at the time of this issue, but there may be changes of specifications for improvements. Contact manufacturer or local sales company for such changes. Brother industries, Ltd.
I. PRINCIPAL MECHANISMS 1. 2. 3. MECHANICAL CHART ............................................................................ 2 POWER TRANSMISSION CHART .......................................................... 3 MICROCOMPUTER-CONTROLLED MAIN MOTOR (B375, B376 AND B377) ..........................................................................
1. MECHANICAL CHART * ** This part is not installed on the B373, B375 and B376 since they are not installed with the automatic thread cutter. This part is not installed on the B373 since it is not an electronic model.
2.
(B) Mechanism of feed dog and oscillating hook movement -4-
(C) Automatic 1-step BH mechanism -5-
3. MICROCOMPUTER-CONTROLLED MAIN MOTOR (B375, B376 AND B377) The sewing machine's main motor requires a constant rotation at all speeds, regardless of changes in the load, power supply or temperature. In addition, to make the machine easy to use, it should take into account that the machine should run slowly when starting sewing and the needle should be in the down position when stopping to automatically cut the thread (for B377). The needle should be in the up position when it stops (for B375 and B376).
II. TROUBLES AND CHECK POINTS 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. Machine skips stitches. ........................................................................... 9 Fabric does not feed. .............................................................................. 9 Fabric does not feed straight. .................................................................. 9 Upper thread breaks at start. ......................................................
The thread cutter does not operate correctly. (B377) .............................. 14 The upper and lower threads are not cut. (B377) .................................... 14 The upper thread is not cut. (B377) ......................................................... 15 The lower thread is not cut. (B377) .......................................................... 15 The machine locks up while cutting the thread. The moving blade does not return to its correct position. (B377) ..............................
PROBLEM 1. Machine skips stitches. CAUSE 1. 2. 3. 4. 5. 6. 7. 8. CORRECTION Improper setting of the needle. Bent or blunt needle. Improper threading. Improper combination of needle/ thread/fabric. Stretch fabric is used. Set the needle correctly. Change the needle. Reset threading correctly. Select correct combination of needle/ thread/fabric. Use stretch fabric needle. Improper timing of the needle and rotary hook. Improper height of the needle bar.
PROBLEM 8. Needle breaks. CAUSE CORRECTION 2. Needle hits inner rotary hook. 3. Needle hits needle plate. 4. 5. 7. 8. Bent or blunt needle. Improper clearance between the needle and the outer rotary hook. Machine feeds while needle is in the fabric. Needle flows. Fabric is pulled excessively. 1. 2. 3. 4. Play of worm/pattern cam gear. Play of lower shaft. Play of upper shaft. Noise from rotary hook. Adjust to proper gearing. Adjust play of the lower shaft. Adjust play of the upper shaft.
PROBLEM 17. The light does not turn on even after the power is turned on. (B375, B376 and B377) CAUSE 1. Replace either the AC cord or the motor control unit. 6. The voltage on both ends of connector SOURSE is not 120V or 230V AC when the AC cord is inserted. The resistance on both ends of the power switch is not less than 1 W when the power is turned on.* The fuse is broken. The light does not turn on. (The light may be damaged or deteriorating or it may have a bad connection.
PROBLEM 19. The motor does not run smoothly or it does not run at a high speed. (B375, B376 and B377) CAUSE 1. 2. 3. 4. 5. 6. 7. 8. 20. Even after the machine is started, it stops suddenly. (B375, B376 and B377) 1. 21. The speed at which the machine operates cannot be adjusted. (B375, B376 and B377) 1. 2. 2. 3. 4. 22. The needle does not stop in the down position. (B377) The needle does not stop in the up position. (B376 and B375) 1. 2. 3. 4.
PROBLEM 23. The machine does not operate if the reverse sewing button is pressed or does not operate at a slow speed if the button is pressed while the machine is running. (However, the machine does not operate at slow speed when the foot controller is being used.) (B375, B376 and B377) 24. The machine stops immediately after bobbin winding is started. (B375, B376 and B377) CAUSE 1. The BT switch does not work. 2. Inferior BT switch.
PROBLEM 26. The thread cutter does not operate correctly. (B377) 1. 2. 3. 4. 5. 6. 27. The upper and lower threads are not cut. CAUSE The thread cutter solenoid lever does not move easily. The resistance between pins 1 and 2 of the thread cutter solenoid connector (J12) is not between 15 and 19 W.* The thread cutter switch is not operating. The thread cutter switch is not operating properly.
PROBLEM 28. The upper thread is not cut. (B377) CAUSE CORRECTION The machine skips stitches. (Refer to"1. Machine skips stitches. "in" TROUBLES AND CHECK POINTS".) Refer to the related items. The thread cutter cam is out of phase. Check that the thread cutter cam (lower shaft) and the outer rotary hook are correctly in phase. The moving and fixed blades are not sharp. Replace with new blades. 29. The lower thread is not cut.
III. HOW TO ADJUST THE ELEMENTS 1. ADJUSTMENT OF EACH CONTROL UNIT ............................................ 18 2. ADJUSTMENT OF THE TIMING BETWEEN THE UPPER AND LOWER SHAFTS ..................................................................................... 19 3. ADJUSTMENT OF THE MOTOR BELT AND TIMING BELT TENSIONS ....................................................................... 20 4. ADJUSTMENT OF THE NEEDLE POSITION AND NEEDLE SWING ..... 21 5.
24. ADJUSTMENT OF THE BOBBIN WINDING SWITCH (B375, B376 AND B377) .......................................................................... 41 25. ADJUSTMENT OF THE PF (PRESSER FOOT) SWITCH (B375, B376 AND B377) .......................................................................... 42 26. ADJUSTMENT OF THE THREAD CUTTER SWITCH (B377) ................. 43 27. FORWARD AND REVERSE FEEDING FOR STRAIGHT STITCH .......... 44 28. ADJUSTMENT OF THE INNER ROTARY HOOK TENSION ................... 45 29.
1. ADJUSTMENT OF EACH CONTROL UNIT 2. Back and forth seam at automatic reverse pattern 5. Bar tack feeding at buttonhole 3. Forward feeding 4. Forward and reverse feeding at buttonhole 1.
2. ADJUSTMENT OF THE TIMING BETWEEN THE UPPER AND LOWER SHAFTS STANDARD When the mark on the horizontal feed cam of the upper shaft is horizontal, the mark on the thread cutter cam of the lower shaft should be 5° above horizontal. (Turn the pulley counterclockwise.) ADJUSTMENT 1. 2. 3. Remove the timing belt from the horizontal feed cam, the tension pulley and timing pulley D.
3. ADJUSTMENT OF THE MOTOR BELT AND TIMING BELT TENSIONS STANDARD There should be 4 ~ 6 mm of slack on the motor belt and 3 ~ 4 mm of slack on the timing belt when the center of each belt is pushed with about 200 g pressure. ADJUSTMENT Timing belt 1. Loosen the screw on the tension pulley. 2. Adjust the tension pulley position. 3. Tighten the screw on the tension pulley. Motor belt 1. Loosen the two motor holder screws. 2. Move the motor holder to adjust the belt slack. 3.
4. ADJUSTMENT OF THE NEEDLE POSITION AND NEEDLE SWING STANDARD Set pattern dial to zigzag stitch. The needle should drop in the center of the needle plate hole when the zigzag width dial is set to "0". The needle should drop in the needle hole balanced when the zigzag width dial is set to the maximum. Needle swing on the way up from the lowest position to needle plate should be less than 0.15 mm and that on the way down from needle plate to the lowest position should be less than 0.05 mm. ADJUSTMENT 1. 2.
5. MAXIMUM STITCH WIDTH WHEN SET AT STRAIGHT (LEFT) AND ZIGZAG STITCH STANDARD Left end of straight stitch should be the same position as left end of zigzag stitch. ADJUSTMENT 1. 2. 3. 4. 5. 6. Lower the feed dog using the drop lever, then place a piece of paper on the needle plate and lower the presser foot. Set the pattern dial to the zigzag stitch and set the zigzag width dial to the maximum so that the needle moves to the left. Drop the needle into the paper by turning the pulley.
6. ADJUSTMENT OF THE ROTARY HOOK (NEEDLE AND OUTER ROTARY HOOK CLEARANCE) STANDARD When the pattern dial is set to the straight stitch, the zigzag width dial is set to the maximum, and the needle is between 2.8 and 3.2 mm above its lowest point, the pointed end of rotary hook should meet with the right side of needle. Under this condition, clearance between the hook and the needle (#14) should be less than 0.1 mm and the hook should not hit the needle. ADJUSTMENT 1. 2. 3. 4. 5. 6.
7. ADJUSTMENT OF THE NEEDLE BAR HEIGHT STANDARD When the pattern dial is set to the straight stitch, the zigzag width dial is set to the maximum and the pointed end of the rotary hook contacts the right side of the needle, the distance from the top of the needle eye to the bottom of the outer rotary hook point should be 0.9 ~ 1.3 mm. ADJUSTMENT 1. 2. 3. 4. 5. Set the pattern dial to straight stitch "2" and set the zigzag width dial to the maximum.
8. FORWARD AND REVERSE SEWING FOR TRIPLE ZIGZAG STRETCH STITCH STANDARD When pattern dial is set to triple zigzag stretch stitch, there should be no difference between forward and reverse feed. ADJUSTMENT 1. 2. 3. 4. Set the pattern dial to the zigzag stitch, the zigzag width dial to the maximum, and the stitch length dial to "SS". Loosen the screw for adjustment of the nut. Adjust forward and reverse feeding by turning the nut. Tighten the screw.
9. ADJUSTMENT OF FEED STANDARD When stitch length dial is set to "0", stitch length should be 0 mm. ADJUSTMENT 1. 2. 3. 4. Set the pattern dial to the zigzag stitch, the zigzag width dial to the maximum and the stitch length dial to "0". Loosen the nut for forward feed adjusting screw. Adjust forward feeding by turning the screw. Tighten the nut.
10. POSITION OF INNER ROTARY HOOK STOPPER STANDARD Inner rotary hook stopper should hold inner rotary hook by 1.9 ~ 2.1 mm as shown in drawing. ADJUSTMENT 1. 2. 3. Loosen the screw on inner rotary hook stopper. Adjust the position of inner rotary hook stopper. (Face A on inner rotary hook and feed direction should be at right angles.) Tighten the screw. Face A 1.9 ~ 2.
11. POSITION OF FEED DOG STANDARD When the upper shaft is rotated once with the maximum feed, the feed dog should not contact the needle plate on the left and right. When the feed dog is in its initial feed position (as far forward as possible), the clearances between the feed dog and the needle plate should be 0.3 ~ 0.8 mm. ADJUSTMENT 1. 2. 3. 4. 5. 6. 7. Loosen two screws on the horizontal feed plate. Adjust the left and right sides of the feed dog. Tighten two screws.
12. HEIGHT OF FEED DOG STANDARD Feed dog should be higher than the needle plate by 0.9 ~ 1.1 mm when the feed dog is raised to its highest position. ADJUSTMENT 1. 2. 3. 4. Raise the feed dog using the drop lever, then raise the feed dog to its highest position by turning the pulley. Loosen the screw for vertical feed finger. Adjust the height of the feed dog by turning vertical feed finger. Tighten the screw. 0.9 ~ 1.
13. HEIGHT OF PRESSER BAR STANDARD The clearance between presser foot and needle plate should be 6.0 ~ 6.5 mm. ADJUSTMENT 1. 2. 3. 4. Raise presser foot. Loosen the screw on presser bar guide bracket. Adjust height of presser bar. (Presser foot should be parallel to feed dog.) Tighten the screw. 6.0 ~ 6.
14. POSITION OF N.P. (NEEDLE POSITION) SHUTTER (B375, B376 AND B377) STANDARD The needle position shutter works when the needle bar is 1.9 mm below its highest position (approx. 37° counterclockwise from the topmost needle bar position). ADJUSTMENT 1. 2. 3. 4. 5. Turn the pulley counterclockwise until the needle is 1.9 mm below its highest position. Remove the two screws on the sensor PC board of the controller PC board assembly, then remove the sensor PC board. Loosen the screw on the rotary shutter.
15. ADJUSTMENT OF THE THREAD TENSION DIAL STANDARD When thread tension dial is set to "4" and presser foot is lowered, upper thread tension should be 33 ~ 38g using polyester thread #60. ADJUSTMENT 1. 2. 3. 4. Set thread tension dial to "4", put polyester thread between tension discs and lower presser foot. Loosen the screw for thread tension control screw. Measure thread tension using tension gauge and adjust tension to 33 ~ 38g by turning thread tension control screw. Tighten the screw.
16. ADJUSTMENT OF THE THREAD TENSION UNIT (B375, B376 AND B377) STANDARD When polyester thread (#60) is passed through the thread tension unit, a tension gauge should measure the thread tension to be 8 ~ 12 g. ADJUSTMENT 1. 2. Pass polyester thread (#60) through the thread tension unit and lower the presser foot. With a screwdriver, turn the adjusting screw to adjust the thread tension.
17. SETTING OF THE STITCH LENGTH DIAL HOLDER STANDARD The mark on the feed adjusting cam faces straight forward when the stitch length dial is set to "SS". ADJUSTMENT 1. 2. 3. Turn the stitch length dial to "SS". Adjust the feed adjusting cam so that its mark faces straight forward. Install the stitch length dial holder using the two screws.
18. POSITION OF THE PATTERN INDICATION PLATE STANDARD Each pattern number should be in the center of the pattern indicator window each time the pattern dial is set. ADJUSTMENT 1. 2. 3. 4. Set the pattern dial to "3". (The second position when turning the pattern dial clockwise after fully turning it counterclockwise.) Loosen the screw on the indication gear B. Align the holes in the indication gear A and the indication gear holder. Tighten the screw on the indication gear B.
19. BUTTONHOLE ADJUSTMENT (FORWARD AND REVERSE FEEDING) STANDARD 1. When the stitch length dial is set to "F" during buttonhole sewing, the left leg should be from the right leg (50 ~ 60 stitches/20 mm). +10 0 stitches/20 ADJUSTMENT 1. 2. 3. 4. 5. 6. mm Set the stitch length dial to "F". Set the pattern dial to "1" and check the stitching of the right leg.
20. BUTTONHOLE ADJUSTMENT (BAR TACK FEEDING) STANDARD The feeding of a bar tack should be less than 10 stitches/1 mm. ADJUSTMENT 1. 2. Set the pattern dial to "1", then sew a buttonhole. Turn the bar tack adjusting screw to adjust the bar tack. NOTE Turn the screw to the left to move the bar tack forward; turn the screw to the right to move the bar tack backward.
21. BUTTONHOLE ADJUSTMENT (THE LENGTH OF THE BUTTONHOLE AND THE PRESSURE OF THE BH LEVER) STANDARD The length of buttonhole should be 21 ~ 23 mm, when the button is 20.0 mm in diameter. The pressure needed to pull the BH lever forward should be 50 ~ 110 g. ADJUSTMENT 1. 2. 3. 4. 5. Loosen the screw on BH change arm. Adjust the position of BH lever according to drawings below. Tighten the screw. Loosen the screw for the eccentric nut.
22. ADJUSTMENT OF THE BOBBIN WINDING STANDARD Thread should be wound parallel to the bobbin and be wound 75 ~ 85% of the outer-diameter of bobbin. ADJUSTMENT 1. 2. 3. 4. 5. 6. In case bobbin thread is wound unbalanced, loosen the screw for bobbin winder thread guide slightly. Move bobbin winder thread guide vertically so that the bobbin thread is balanced when it is wound. Tighten the screw. Loosen the screw for the bobbin presser slightly.
23. ADJUSTMENT OF THE REVERSE SEWING SWITCH (B375, B376 AND B377) STANDARD The clearance between the BT switch and the reverse sewing lever should be 1.0 ~ 1.5 mm. ADJUSTMENT 1. 2. 3. Loosen the screw on the BT switch. Adjust the clearance between the BT switch and the reverse sewing lever. Tighten the screw on the BT switch. NOTE Check that the BT switch turns on when the reverse sewing button is pressed and the stitch length dial is set to "0". 1.0 ~ 1.
24. ADJUSTMENT OF THE BOBBIN WINDING SWITCH (B375, B376 AND B377) STANDARD When bobbin winder is moved to bobbin presser, bobbin winding switch should be on. When bobbin winder is returned, the clearance between bobbin winder and switch should be 1.0 ~ 1.5 mm. ADJUSTMENT 1. 2. 3. 4. Move bobbin winder to the left. Loosen the screw. Adjust the switch by moving it left to right. Tighten the screw. 1.0 ~ 1.
25. ADJUSTMENT OF THE PF (PRESSER FOOT) SWITCH (B375, B376 AND B377) STANDARD The PF switch should bend 1 ~ 2 mm when the presser foot is raised. ADJUSTMENT 1. 2. 3. 4. Loosen the screw on the PF switch. Raise the presser foot. Adjust so that the PF switch bends 1 ~ 2 mm. Tighten the screw on the PF switch.
26. ADJUSTMENT OF THE THREAD CUTTER SWITCH (B377) STANDARD When the thread cutter operation lever is operated while the needle is lowered and the latch is engaged, the thread cutter switch should go on between the point where the latch is engaged and the position where the thread cutter operation lever stops. ADJUSTMENT 1. 2. 3. 4. 5. 6. Turn off the power, then turn the pulley until the needle is lowered.
27. FORWARD AND REVERSE FEEDING FOR STRAIGHT STITCH STANDARD There should be no difference in the length of a forward stitch as compared to a backward stitch when the stitch length dial is set to "2". ADJUSTMENT 1. 2. 3. 4. 5. 6. Set the pattern dial to "2". Set the stitch length dial to "2". Sew forward stitch on a piece of paper by turning the pulley then push the reverse sewing button and sew backward. Loosen the screw on the reverse sewing finger. Adjust the position of the reverse sewing finger.
28. ADJUSTMENT OF THE INNER ROTARY HOOK TENSION STANDARD When polyester thread (#60) threaded through the inner rotary hook is slowly pulled with a tension gauge, the tension should be 10 ~ 12 g. ADJUSTMENT 1. 2. Using polyester thread (#60), thread the inner rotary hook as usual, then slowly pull on the thread with a tension gauge. Using a screwdriver, turn the tension spring adjusting screw to adjust the tension. NOTE After adjusting the tension, apply locking paint to the screw.
29. NEEDLE THREADER CAUTION 1. 2. 3. 4. 5. 6. 7. 8. Needle threader accepts only circle marked needle and thread combinations. * marked combinations is not recommended since it might lead to the breakage of needle threader or imperfect performance. Lower the presser foot when you use needle threader. Nylon transparent thread is applicable in needle #14 ~ 16. Do not turn the pulley when you use needle threader. Do not touch needle threader when machine is running. Needle #9 might be hard to thread.
30. NEEDLE THREADER (CHECKING THE HOOK POSITION IN HORIZONTAL DIRECTION) STANDARD The measure from inside of the hook guard to the center point of hook is 0.42 mm. CHECK Prepare 5 pcs. of brand-new sewing HA´1 (#14) and check by changing all of these. After Checking A. In case that, hook gets through eyelet of all needles...........................Nothing is the matter. B. In case that, hook does not get through eyelet of all needles..............Adjust by bending hook. C.
31. NEEDLE THREADER (REPLACEMENT) HOW TO EXCHANGE THE NEEDLE THREADER When replacing the needle threader, follow the procedure below. 1. 2. 3. 4. Remove the needle and lower the presser foot. With the index fingers of both hands, push down on the needle threader to remove it. To install a new needle threader, align the flat surfaces on the needle threader and the shaft as shown in fig. A. Attach the needle threader until the guide on the needle threader fits into the groove on the shaft.
32. NEEDLE THREADER (CHECKING THE HOOK POSITION IN VERTICAL DIRECTION) STANDARD 1. 2. The clearance between the top of hook and the top of needle eye is zero. Threading is capable when needle is located higher than 9.0 mm from the needle plate. CHECK (Refer to the illustration.) Case A Hook position is too high. (Hook hits needle and cannot get through needle eye.) Case B Hook position is too low. (Hook gets through needle eye but it catches bottom part of needle.
33. NEEDLE THREADER (ADJUSTMENT OF THE HOOK POSITION IN VERTICAL DIRECTION) CASE A (Hook point is too high) 1. 2. 3. Set the needle position at right and loosen the screw. Adjust needle threader slightly down and check the clearance between the top of hook and top of needle eye is zero. Check if part (a) and part (b) is parallel . CASE B (Hook point is too low) 1. 2. 3. Set the needle position at right and loosen the screw.
34. ADJUSTMENT OF THE THREAD CUTTER NOTCH CAM POSITION (B377) STANDARD The thread cutter latch should be disengaged when the needle bar is 1.6 mm below its highest position (approx. 34° counterclockwise from the topmost needle bar position). ADJUSTMENT 1. 2. 3. 4. 5. Turn off the power, then turn the pulley counterclockwise to lower the needle. Press down on the thread cutter operation lever until the latch is engaged. Loosen the two screws on the thread cutter notch cam.
35. ADJUSTMENT OF THE THREAD CUTTER FRAME INSTALLATION POSITION (B373, B375 AND B376) STANDARD 1. 2. The thread cutter frame should be positioned so that there is no space between it and the side of the arm. It should be positioned so that the space between the thread cutter frame and the outer rotary hook is 1.9 ~ 2.2 mm. ADJUSTMENT 1. 2. 3. Loosen the two mounting screws. Position the thread cutter frame assembly. Tighten the two mounting screws. 0 mm Screw 0 mm Screw 1.9 ~ 2.
IV. HOW TO CHANGE THE PARTS 1. REMOVING THE COVERS ..................................................................... 54 2. LAMP REPLACEMENT ............................................................................ 55 3. LEAD WIRES ARRANGEMENT .............................................................. 56 ........................................................................................
1. REMOVING THE COVERS 1. 2. 3. 4. 5. 6. 7. Remove the face plate screw, then remove the face plate by pulling it off to the left. Remove the free-arm cover screw, then remove the free-arm cover by pulling it off to the left. Pull the thread cutter operation lever off toward you.
2. LAMP REPLACEMENT 1. 2. 3. Loosen the screw of face plate. Remove face plate.
3.
B375, B376 120V Spec. GND (JW18) Transformer CN1 Lamp unit CN3 Reverse switch CN6 Presser foot switch CN7 Bobbin winder switch To SS-VR connector +5 V (JW15) Fuse MOTOR Main motor Sensor P. C. B. assembly F. C. Pin jack assembly Power switch AC Inlet B375, B376 230V Spec GND (JW18) Transformer CN1 Lamp unit CN3 Reverse switch CN6 Presser foot switch CN7 Bobbin winder switch To SS-VR connector +5 V (JW15) Fuse MOTOR Main motor Sensor P. C. B.
B377 120V Spec. GND (JW18) Transformer CN1 Lamp unit CN3 Reverse switch CN4 Thread cut switch CN6 Presser foot switch CN7 Bobbin winder switch To SS-VR connector +5 V (JW15) Fuse To Solenoid unit +30 V (D5 Cathode) MOTOR Main motor Sensor P. C. B. assembly F. C. Pin jack assembly Power switch AC inlet B377 230V Spec.
(B375, B376) Speed Volume (B377) - 59 -
- 38 - B373 (STAR110, PS-2200) B375 (STAR120E, PS-2300) B376 (STAR130E, PS-2400) B377 (STAR140E, PS-2500) T7110099
