service manual brother xl3750

SERVICE MANUAL FOR

XL2600i

XL3500i

XL3600

BM3600

XL3750

9. 2006.6. 2007.

CONTENTS

Disassembly ProcedureDisassembly Procedure......................................................................................1 - 1Needle Bar-Presser Unit Disassembly ...............................................................1 - 5Lower Shaft Unit Disassembly............................................................................1 - 7Thread Tension Disassembly .............................................................................1 - 8Z Dial Assy. Disassembly ...................................................................................1 - 9

Assembly ProcedureAssembly Procedure.........................................................................................1 - 10Front Cover.......................................................................................................1 - 10Rear Cover .......................................................................................................1 - 11Thread Tension Assembly ................................................................................1 - 15Needle Bar-Presser Unit Assembly (With Needle Thread)...............................1 - 16Lower Shaft Unit Assembly...............................................................................1 - 18Z Dial Assy. Assembly ......................................................................................1 - 21An Exchange Method Of Outer Rotary Hook Assy...........................................1 - 22

AdjustmentAdjustment of the Timing Belt Tension ...............................................................2 - 1Adjustment of the Motor Belt Tension.................................................................2 - 2Adjustment of the Needle Bar Stopper ...............................................................2 - 3Adjustment of the Needle Sidewise Movement (Needle Swing Timing).............2 - 4Adjust of the down position back and forth for the presser foot..........................2 - 5Adjustment of the Needle Swing.........................................................................2 - 6Adjust of the down position of the straight line on the left base line (right / left) ...2 - 7Adjustment of the down position of the bar track (BH “ac”) on the left base line (right / left) ...2 - 8Adjustment of the Needle Bar Height .................................................................2 - 9Clearance between the needle and the rotary hook point adjustment..............2 - 10Adjustment of the Position of the Inner Rotary Hook Rotation Prevention Bracket.......2 - 11Adjustment of the Upper Thread Tension.........................................................2 - 12Adjustment of the Inner Rotary Hook (Lower Thread) Tension ........................2 - 13Adjustment of the Thread Winding (Uneven Bobbin Winding and Amount of Thread Winding) ....2 - 14Adjustment of the feed of the bar track (BH “a”). ..............................................2 - 15Adjustment of the feed......................................................................................2 - 16Adjustment of the feed......................................................................................2 - 17Adjustment of the feed of the left over edging button hole (BH ”b”)..................2 - 18Adjustment of the BH length .............................................................................2 - 19

1 - 1

Disassembly Procedure1. Remove the needle plate B.2. Remove the one screw (taptite cup P M4 x 20) securing the face plate and then remove the face plate to the

front.3. Pull out the selection dial on the front face of the front cover.4. Remove the retaining ring E6, and then remove the feed dial.5. Remove the screws fastening the front cover, one in the front (taptite bind B M4 × 10) and six in the back

(five giza tite M 5 × 16, and one giza tite M 3 × 25), to remove the front cover.6. Remove the two screws (taptite, bind B M 4 × 14) to remove the thread conductor A assembly.7. Remove the one screw (taptite, bind B M 4 × 14) to remove the thread conductor B assembly.8. Pull out the reverse stitching knob.

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Disassembly Procedure

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9. Remove the feed connecting holder from the spring. (Ø5 × 21 mm)10. Remove the retaining ring E2.5 that links the BH change arm assy. and the BH connecting rod B.11. Remove the three screws (giza tite 5 × 16), and then remove the selecting unit assy., selecting unit the two

washers and the spacer.12. Remove the spring (Ø6 × 15 mm) of the zigzag lever.13. Remove the retaining ring E2.5 that links the Z linkage and the selection unit and E5 that links the Z linkage

and the needle bar supporter and then remove the Z linkage and the polyester slider.14. Remove the two screws (giza tite 5 × 16) , and then remove the Z dial assy. and the zigzag lever.15. Remove the two screws (giza tite 5 × 16) securing the lower shaft metal retainer to remove it.16. Remove the screw (giza tite 5 × 16) for the feed transmission holder.17. Remove the two screws (giza tite 5 × 16) holding the base plate assembly and remove the feed module.18. Remove the screw (screw bind M3 × 20) holding the lamp and remove the lamp unit.19. Remove the screw (taptite, bind B M4 × 14), and then remove the cord stopper.20. Remove the screw (taptite, bind B M4 × 14), and then remove the cord clamp.

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G G

G

F

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D

D

D

E

E

B

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C

C

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A

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9

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A

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A

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21. Remove the screw (screw, bind M3 × 25) for needle clearance adjustment.22. Remove the screw (screw, pan (S/P washer) M4 x 8) for the BH notch spring plate, and then remove the BH

notch spring plate and the BH spring.23. Remove the two screws (giza tite 5 × 16, taptite, cup P M 4 x 20) of the BH change shaft holder A, and then

remove the BH change shaft holder A.24. Remove the four screws (giza tite 5 × 16) securing the upper shaft metal retainer to remove it.25. Loosen the screw (set screw, socket (FT) M 5 × 5) for the thread take-up lever crank and separate the upper

shaft assembly from the needle bar-presser unit assembly, and then remove the upper shaft assy.26. Remove the tension belt from the upper shaft assembly.27. Remove the two screws (giza tite 5 × 16) securing the needle bar-presser unit assembly and then remove the

needle bar-presser unit assembly.

Q

P

P

P

NN

M

M

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O

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O

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28. Remove the one screw (giza tite 5 × 16) and remove the cord retainer and the bobbin winder spring.29. Cut the band of the cord guide plate, remove the shield wire of the lamp unit.30. Remove the two screws (taptite, bind B M 5 × 16) to remove the bobbin winder assy.31. Remove the one screw (taptite, bind B M 4 × 14) to remove the shield wire clip.32. Remove the two screws (bolt, (S/P washer) M 5 × 12) to remove the motor and the motor belt.33. Remove the two screws (giza tite 5 × 16) to remove the two motor fixed plate.34. Remove the two screws (screws, pan (S/P washer) M 4 × 30) to remove the three pole lamp socket.35. Remove the two screws (taptite, bind B M 4 × 14) to remove the Plate apring, the adjusting plate, and the

adjusting screw.36. Remove the spool pin spring and remove the spool pin.37. Remove the one screw (giza tite 4 × 12) to remove the thread guide assembly.38. Remove the one screw (taptite, pan B (S/P W) 3 × 12) to remove the bobbin presser.

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YY

Y

Y

Y

XX

X

X

X

V

V

W

W

W

W

U

U

[

Z

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\

Z

TT

S

V

S

S

T

V

1 - 5


Needle Bar-Presser Unit Disassembly1. Loosen the screw (set screw socket (CP) M 4 x 4) of the BH change arm, and then remove the BH change

arm.2. Remove the retaining ring E2.5 of the BH change shaft assy., and then remove the BH change shaft assy.3. Remove the needle bar crank rod, and then remove the polyester slider.4. Remove the screw (screws pan (S/P washer) M 3 × 8) of the stud for thread take-up lever supporter by

pulling it out to the right, and them remove the thread take-up lever supporter, the dome spring washer andthe retaining ring E5.

5. Remove the thread take-up lever body and the needle bar crank from the thread take-up lever supporter.6. Remove the screw and the spring at the top of the needle bar supporter and remove the needle bar supporter

from the base holder assembly.

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7. Loosen the one screw (set screw, socket (FT) M 4 × 4) securing the needle bar clamp to remove the needlebar assembly.

8. Remove the one screw (screw, bind M 2.6 × 4) of the thread positioning plate and remove the threadpositioning plate.

9. Remove the one screw (screws pan (S/P washer) M 3 × 8DA) at the bottom of the needle bar supporter andremove the Z fine adjusting plate from the needle bar supporter.

10. Remove the screw (3.57L) to remove the thread take-up lever and the needle bar crank rod.11. Loosen the screw (set screw, socket, (CP) M 5 × 8) securing the presser bar clamp to remove the presser bar

and the spring.12. Remove the one screw (bolt, socket M 3 × 6) for the stopper to remove the stopper.13. Remove the one screw (bolt, socket M 3 × 6) for the needle bar supporter stud holder to remove the needle

bar supporter stud holder assembly.14. Remove the retaining ring E5 and remove the presser lifter.15. Remove the retaining ring CS4 and remove the thread loosening lever and the spring.16. Remove the one screw (screw, bind M 4 × 6) for the lamp holder to remove the lamp holder, and then

remove the one screw (screw, bind M 4 × 6) for the guard plate to remove the guard plate.17. Remove the one screw (screw, bind M 4 × 6) for the BH shaft holder, and remove the retaining ring E3 for

the BH lever holder assy., and then the BH shaft holder and the BH lever holder assy.

18. Remove the one screw (bolt socket M 3 x 6) for the needle holder stopper, and then remove the needle holderstopper.

19. Remove the one screw (screw, bind M 4 × 6) for the BH change shaft holder B, and then remove the BHchange shaft holder B.

20. Remove the one screw (bolt socket M 3 x 6) for the BH lever stopper, and then remove the BH lever stopper.21. Remove the reatainting ring E3 for the BH connecting rod A assy., and then remove the BH connecting rod

A assy.

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9

B

B

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F

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A

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A

A

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Lower Shaft Unit Disassembly1. Remove the two retainer ring E4 and loosen the screw (screw, bind 4 × 14) to remove the feed transmission

lever A and the feed transmission lever B.2. Remove the two screws (screw M4) to remove the needle plate A.3. Remove the inner rotary hook.4. Remove the one screw (screws pan (S/P washer) M 3 × 6) and remove the inner rotary hook rotation

prevention bracket assembly.5. Remove the two screws (screw, bind M 3 × 6) to remove the feed dog.6. Loosen the three screw (set screw, socket (CP) M 4 × 4) for the shaft supporter and remove the rotary hook

assembly.7. Remove the three retainer rings E3 for the vertical feed shaft and the retainig ring CS4 and then remove the

vertical feed shaft, the washer and the vertical lever.8. Loosen the two screws (set screw, socket (CP) M 4 × 4) on the lower shaft set collar and then remove the set collar

and the washer, thrust.9. Remove the one screw (screw, bind M 3 × 6) and remove the feed supporting plate and the feed supporting

plate B.10. Remove the three screws (screw, bind M 3 × 6) to remove the metal retainer B.11. Remove the metal and the washer, thrust.12. Remove the retainer ring E6 from the timing pulley side of the lower shaft, loosen the two screws (set screw,

socket (CP) M 5 × 5), and then remove the timing pulley and the lower shaft bushing.13. Remove the lower shaft assembly.14. Remove the retainer ring E5 from the horizontal feed shaft and loosen the screw (set screw, socket (CP) M 3

× 6), and then remove the horizontal feed shaft.15. Remove the two feed base tension spring.16. Remove the two screws (screws, pan (S/P washer) M 4 × 22) and the two collar to remove the rotary hook

shaft receptacle.17. Remove the retainer ring shaft CS3.5 and then remove the feed arm assy.18. Remove the feed arm supporter.19. Remove the feed adjusting shaft assy.

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Thread Tension Disassembly1. Remove the holding screw (screw, pan M 3 × 4) to remove the notch spring.2. Set the thread tension dial to 9 and remove the thread tension dial shaft.3. Remove the thread tension plate.4. Remove the thread tension adjusting screw from the thread tension plate.5. Remove the following items in the following order: the spring, the washer, the tension spring receptacle, the

thread release plate, the washer, plain, the thread tension disc B, and the thread tension disc A.6. Remove the one screw (screws pan (S/P washer) M 3 × 18DA) and remove the thread take-up spring case

and the thread take-up spring.

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Z Dial Assy. Disassembly1. Remove the two retainig ring E2.5, and then remove the Z dial connecting rod and the Z dial pin.2. Remove the two retainig ring E4, and then remove the Z dial.3. Remove the one screw (taptite, bind B M 3 × 6) and remove the notched spring.4. Remove the retaining ring E2.5, and then remove the zigzag lever and the Z dial connecting rod.

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Assembly ProcedureAssemble and install the units first before attaching the front cover and the rear cover

Front Cover1. Insert the thread tension dial of the thread conductor A assembly into the square hole of the front cover, and

secure with the two screws (taptite, bind B M 4 × 12). 2. Insert the tip of the wire of the thread conductor B assembly by aligning it against the positioning groove of

the front cover and secure with the screw (taptite, bind B M 4 × 12) that sets the protrusion of the threadconductor B into the hole in the front cover.

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1

Assembly Procedure

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Assembly Procedure

Rear Cover1. Temporarily fasten the thread guide assembly with the one screw (giza tite 4× 12).2. Insert the spool pin into the rear cover and then attach the spool pin spring onto it.3. Attach the adjusting plate, Plate apring, and the adjusting screw in this order and secure them with the two

screws (taptite, bind B M 4 × 10).4. Attach the two motor fixed plate with the two screws (giza tite 5 × 16), and then attach the motor holder to

the motor, and then insert the motor fan while attaching the motor belt, and then attach the motor holder andthe cord guide plate with the two screw (bolt, (S/P washer) M 5 x 12).

5. Fasten the three pole socket assembly with the screw (screw, pan (S/P washer) M 3 × 6).6. Route and connect the lamp unit harness and the motor harness, and then attach it with the screw of cord

clamp.7. Secure the bobbin assembly with the two screws (taptite bind B M 5 × 16).8. Fasten the cord retainer and the thread winding spring with the one screw (giza tite 5 × 16).

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Assembly Procedure

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9. Insert the BH change shaft assy. to the BH change shaft holder B on the needle-presser nuit, and then attachthe retaining ring E2.5.

10. Attach the needle bar-presser unit assembly to the rear cover with the two screws (giza tite 5 x 20), and thenInsert the BH change arm assy., and then temporarily fasten the screw (set screw socket (CP) M 4 x 4).

11. Insert the tension belt and the timing belt into the upper shaft assembly, and then attach the upper shaftassembly to the rear cover while inserting the needle bar crank into the hole of thread take-up counterweight.

12. Fasten the screw (set screw, socket (FT) M size 5 × 5) for the thread take-up lever crank at the cut faceposition to connect the upper shaft assembly and the needle bar-presser unit assembly.

13. Attach the upper shaft bearing presser to the shaft bushing (two points) of the upper shaft assembly, and thenfasten the four screws (giza tite 5 x 16).

AA

9

0

09

9

B

A

0

0

0

CC

C

CC

C

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Assembly Procedure

14. Temporarily fasten the screw (screw bind M 3 x 25) for needle clearance adjustment.15. Secure the lamp unit to the base holder assembly with the screw (screw bind M 3 x 20).16. Rinse lower shaft of the feed module and the feed adjusting shaft, and then fit the feed module in the rear

cover and secure it with the two screws (giza tite 5 × 16) of the base plate assembly.17. Attach the feed connecting holder with the screw (giza tite 5 × 16)18. Place the lower shaft metal retainer on the lower shaft metal and fasten it with the two screws (giza tite 5 × 16).19. Insert the hole of the BH change shaft holder A into the change shaft, and then attach it with the two screws. 20. Set the washer in the mounting position on the rear cover.21. Put the worm pulley of the selection unit through the timing belt, and then adjust the pin of the feed

connecting lever and the hole of the feed rod, and then set it in the mounting position on the rear cover.22. Insert the spacer into the hole of the lower left of the unit, and then attach the selecting unit with the three

screws (giza tite 5 x 16).23. Attach the BH change shaft holder B to the BH change arm assy., and then attach the retaining ring E2.5.24. Attach the zigzag lever to the groove of the zigzag link and the shaft of the lower needle holder, and then

attach the retaining ring E4 which connects zigzag link with the selecting unit.25. Attach the Z dial assy. to the body, and then attach the zigzag lever and the Z dial assy. with the retaining

ring E2.5.26. Attach Z dial assy. with the two screws (giza tite 5 x 16).

How to attach the Z dial assy.• Temporarily fasten the screw of the right side.• Turn the Z dial to [0].• Pull over the zigzag lever io the bottom, and pull over the Z dial assy. to the topside, and then lower the

zigzag lever along the groove of the zigzag link.• Fasten the screw of the left side when the roller of the zigzag lever located on the most inferior point of the

groove of the zigzag link.• Fasten the screw of the right side.

27. Attach the pull spring (Ø6 × 15 mm) of the Z linkage.28. Attach the spring.29. Attach the BH spring and BH notch spring plate with the screw (screw pan (S/P washer) M 4 x 8).

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Assembly Procedure

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30. Attach the cord clamp with the screw (taptite bind B M 4 x 14).31. Install the reverse stitching knob.32. Tighten the screws for fastening the front cover, one in the front (taptite bind B M 4 x 14) and six in the back

(five giza tite 5 × 16, and one giza tite 3 × 32), to secure the front cover.33. Attach the F dial, and then attach the retaining ring E6.34. Attach the selection dial on the front face of the front cover.35. Attach the face plate with the screw (taptite, cup P M 4 x 20).36. Attach the.needle plate B.

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Y

XW

W

Z

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V

TT

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VV

U

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Assembly Procedure

Thread Tension Assembly1. Mount the following items in the following order: the tension disc A, the tension disc B, the washer, the

thread release plate, the tension disc washer, the washer, and the spring.2. Mount the thread tension adjusting screw on the thread tension stud aligning it to the thread tension cam

groove in the thread tension dial.3. Set the thread tension dial to 9 and attach the thread tension dial shaft.4. Align the notch spring against the oval hole and secure it with the screw (screw, pan M 3 × 4).5. Attach the thread take-up spring in the second hole from the bottom of the thread take-up spring case so that

the thread guard side fits between two protrusions of the spring case.6. Insert the positioning protrusion of the thread take-up spring case assembly into the square hole of the thread

conductor B, shift it all the way up in the square hole, and secure it with the one screw (screw, pan (S/Pwasher) M 3 × 18DA).

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Assembly Procedure

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Needle Bar-Presser Unit Assembly (With Needle Thread)1. After setting the lever spring in the letter V direction in the U-bend part of the thread loosening lever and

inserting into the base holder shaft, attaché the retaining ring CS4. (The lever spring should be rested on thebase holder on the left side and on the upper side of the U-bend part on the right side.)

2. Insert the presser lifter in the presser lifter shaft and attach the retainer ring E4.3. Align the U groove of the base holder against the protrusion of the needle bar stopper and temporarily fasten

it with the one screw (bolt, socket, M 3 × 6) from the back.4. Set the screw (set screw, socket (CP) M 5 × 8) on the presser bar clamp, insert the presser bar into the base

holder, the presser bar clamp, and the spring in this sequence, and temporarily fasten the screw (set screw,socket (CP) M 5 × 8).

5. Insert the needle holder rod A assy. into the hole of the base holder assy, and then attach it with retaining ring E3.6. Align the positioning hole of the guard plate to the protrusion of the lamp holder, and then fasten the screw

(screws, bind M 3 × 4) from the rear side.7. Align the positioning hole of the lamp holder to the protrusion of the base holder, and then fasten the screw

(screws, bind M 4 × 6) from the rear side.8. Align the positioning hole of the BH change shaft holder B to the protrusion of the base holder, and then

fasten the screw (screws, bind M 4 × 6) from the rear side.9. Insert the BH lever holder assy. into the hole of the BH shaft holder, and then attach the retaining ring E3.10. Align the end of BH lever holder to the U groove of the BH change shaft holder A, and then align the

positioning hole of the BH shaft holder to the protrusion of the base holder, and then fasten the screw (screws,bind M 4 × 6) from the rear side.6.Attach the retaining ring E5 to the stud for thread take-up lever supporter.

11. Attach the retaining ring E5 to the stud for thread take-up lever supporter.12. Insert the dome spring washer into the stud for thread take-up lever supporter with its convex side facing the

retaining ring.13. Insert the thread take-up lever supporter into the stud for thread take-up lever supporter.14. Insert the stud for thread take-up lever supporter into the base holder and secure it with the one screw

(Phillips, pan head screw with spring and plain washers, size 3 × 8DB).15. Insert the riveting stud for the Z fine adjusting plate from behind the needle bar supporter and temporarily

fasten it with the screw (Phillips, pan head screw with spring and plain washers, size 3 × 8DB).16. Temporarily insert the needle bar into the needle bar supporter, run it through the thread positioning plate

and the needle bar block, and then attach the thread positioning plate withe the screw (screws, bind M 2.6 ×4) and temporarily fasten with the screw (set screw, socket (FT) M 4 × 4).

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01

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Assembly Procedure

17. Set the needle bar supporter in the base holder, insert the push spring into the gap between the needle barsupporter and the base holder, and force the needle bar supporter stud in.

18. Attach the lock nut to the needle bar supporter stud, turn it until it levels with the base holder, and thentighten it.

19. Temporarily insert the needle bar supporter arm into the pin of the needle bar supporter.20. Insert the needle bar supporter arm into the riveting pin for the needle bar supporter stud holder and attach

the retaining ring E2.21. Insert into the U groove of the base holder of the needle bar supporter stud holder and temporarily fasten

with the one screw (bolt, socket M 3 × 6) approximately in the center of the oval hole of the needle barsupporter stud holder.

22. Align the U groove of the needle holder stopper against the protrusion of the needle bar stopper andtemporarily fasten it with the one screw (bolt, socket, M 3 × 6) from the back.

23. Assemble with the thread take-up lever body and the needle bar crank and fasten with the Phillips, flatcountersunk head screw, size 3.57.

24. Insert the riveting stud of the thread take-up lever body for the thread take-up lever supporter into the threadtake-up lever supporter.

25. Insert the needle bar crank rod in to the needle bar crank and the needle bar clamp shaft.

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Lower Shaft Unit Assembly1. Insert the push spring in the feed adjuster assembly which is then inserted into the shaft receptacle of the base

plate from the left.2. Insert the feed arm receptacle to the end face of the base plate.3. Snap on the retainer ring E6 in the retainer spring groove on the left of the lower shaft and attach the thrust

washer on the shaft from the left.4. Insert the lower shaft assembly into the base plate.5. Attach the lower shaft metal on the left of the lower shaft, set the metal retainer B, and secure with the three

screws (screws, bind M 3 × 6).6. After attaching the thrust washer and the set collar on the left of the lower shaft, slide the set collar toward

the metal, and tighten the screw (set screw, socket (CP) M 4 × 4).7. Insert the vertical feed shaft into the base plate, slide the vertical finger and the washer on the shaft, and

attaché the retainer rings E3 on the inner left of the base plate as well as outside of the vertical finger (on boththe left and the right).

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Assembly Procedure

8. Attach the polyslider first and then the feed arm B on the riveting stud of the feed arm A, and apply theretainer ring shaft CS.

9. Insert the feed arms A and B assembly into the base plate from below, and place the feed regulator slide shaftinside the feed adjuster.

10. After inserting the polyslider between the feed arm A and the base plate, insert the horizontal feed shaft from the left.11. Snap on the retainer ring E5 to the horizontal feed shaft from inside of the base plate.12. Slide the polyslider and the set collar on the horizontal feed shaft from the left, place them on the left hand

side, and tighten the two screws (set screws, socket, CP, size 4 × 4).13. Tighten the screw (set screw, socket (CP) M 4 × 10) on the vertical adjuster.14. Assemble the screw (set screw, socket (CP) M 4 × 10) with the lock nut, drive it into the feed base, and then

tighten the lock nut. 15. Slide the feed base on riveting stud of the feed arm A and snap on the retainer ring shaft CS to the shaft on

the left hand side.16. Attach the vertical rod between the vertical adjuster and the vertical finger.17. Attach the feed tension spring on the feed base and the base plate.18. Align the protrusion of the feed auxiliary plate B against the groove in the feed auxiliary plate and fasten

with the screw (screws, bind M 3 × 4).19. Attach the lower shaft metal to the right hand side of the lower shaft and snap on the retainer ring E6 in the

retainer ring groove on the inner side of the lower shaft.20. Turn the lower shaft so that the spring pin of the lower shaft gear is at its lowest position and the horizontal

feed cam faces to the front. Slide the timing pulley D on the shaft with the pulley's screw head facing to theright, position the pulley so that its screw (set screw, socket (CP) M 5 × 5) faces to the front and the otherscrew to the top, and then temporarily tighten the screws.

21. Set the Class 2 nut 4 on the bottom side of the feed transmission lever and temporarily fasten with the screw(screws, bind 4 × 14).

22. Attach the feed transmission lever to the feed adjuster shaft, snap on the retaining ring E4 in the retainer ringgroove on the right, slide the feed transmission lever toward the retainer ring, and temporarily fasten it.

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9

B

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Assembly Procedure

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23. Temporarily insert the screw (set screw, socket (CP) M 4 × 4) in the rotary hood shaft receptacle andtemporarily fasten the rotary hood shaft receptacle with the screw (screw, pan (S/P washer) M 4 × 22).

24. While the spring pin of lower shaft gear facing down and the horizontal feed can facing to the front, insert therotary hook so that is reference point faces to the front and tighten the screw (set screw, socket (CP) M 4 × 4).

25. With a force of about 400g pushing on the outer rotary hook shaft, and then fasten the screw ((set screw, socket(CP) M 4 × 4).

26. Verify that there is reasonable backlash between the rotary hook and the lower shaft. (The backlash alongthe perimeter should be 0.8 mm max.)

27. Attach one end of the backlash eliminating spring to the same hole in the feed base as for the feed basetension spring and the other end to the feed base plate.

28. Secure the feed dog with the screw (screw, bind M 3 × 6).29. Set the inner rotary hook.30. Temporarily fasten the needle plate A with the M4 screw.31. Align the mounting hole of the inner rotary hook rotation prevention bracket against the protrusion and

temporarily fasten it with the screw (screw, pan (S/P washer) M 3 × 6).

(XL)

(BM)

N

N

S

N

NO

M

M

R

R

TT

T

U

U

R

M

MO

M

1 - 21

Assembly Procedure

Z Dial Assy. Assembly1. Pull over the notched spring to the end of upper side, and then fasten the one screw (taptite bind B M 3 x 6).2. Insert the Z dial into the shaft, and attach the retaining ring E4.3. Insert the Z dial pin into the Z dial and Z dial connecting rod, and attach the two retaining ring E2.5

1

1

2

2

33

3

1 - 22

Assembly Procedure

Ass

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An Exchange Method Of Outer Rotary Hook Assy.(Remove the front cover refer to ‘Disassembly Procedure”)

1. Remove the two screws (screw M4) to remove the needle plate A.2. Remove the one screw (screw, pan (S/P washer) M3 x 6) to remove the inner rotary hook bracket assy.3. Loosen the one screw (set screwsocket (CP) M4 x 4) of shaft supporter, and pull the outer rotary hook shaft.4. Remove the outer rotary hook assy. while pushing the feed dog to the back side.5. Insert outer rotary hook assy. so that the reference hole on the outer rotary hook faces the front, and tighten

the screw (set screw socket (CP) M4 x 4), and then hold the pin spring roll of lower shaft gear with thebottom, and hold the feed cam with the rear.

6. Attach the inner rotary hook bracket assy. with the screw (screw, pan (S/P washer) M 3 × 6).7. Attach the needle plate A with the screw (screw M4).*Key point

• After exchage, check the needle bar quantity of rise and needle bar height.

71

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62

62

35

4 5

2 - 1

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1. Adjustment of the Timing Belt Tension• When pulling on the middle portion of the timing belt with a force of 3 N (300 g), there should be a slack of

3 to 4 mm.1 Loosen the screw (Screw, pan (S/P washer) M 4 × 8 DA) fastening the tension pulley holder.2 Adjust the belt tension by moving the tension pulley holder up or down.3 Tighten the screw (Screw, pan (S/P washer) M 4 × 8 DA) to secure the tension pulley holder.4 Check the timing belt tension again.

3 - 4 mm

Screw, pan (S/P washer) M4 × 8DA

Tension pulley holder

Tension guage

3N(300g)

Adjustment

2 - 2

Adjustment

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2. Adjustment of the Motor Belt Tension• When pulling on the middle portion of the motor belt with a force of 1 N (100 g), there should be a slack of 3

to 4 mm.1 Loosen the two screws (Bolt, (S/P washer) M 5 × 12) fastening the motor holder.2 Adjust the belt tension by moving the motor holder up or down.3 Tighten the two screws (Bolt, (S/P washer) M 5 × 12) to secure the motor holder.4 Check the motor belt tension again.

3 - 4 mm

Bolt, (S/P washer) M5 × 12

Motor holder

Tension guage

1N(100g)

2 - 3

Adjustment

3. Adjustment of the Needle Bar Stopper• The needle tip should not touch the needle plate when the needle bar is lowered and the needle bar support is

pushed to the right. The needle bar support should not contact the stopper when the needle is at the rightdown position with the maximum zigzag width setting.

1 Turn the selection dial to [3].2 Turn the dial to [5] to maximize the zigzag width. 3 Turn the pulley to lower the needle bar until the needle tip is level with the top face of the needle plate.4 Loosen the screw (bolt, socket, size M3 x 6) securing the stopper. 5 Adjust the stopper position (left/right) so that the needle tip does not contact the needle plate when the needle

bar support is pushed to the right. 6 Tighten the screw (bolt, socket, size M3 x 6) to secure the stopper.7 Turn the pulley to verify that the needle bar support does not contact the stopper when the needle is swung to

the right. If it contacts the stopper, repeat from step 1.

0.3 - 0.7 mm

stopper

Needle barsupporter

Adjustment of the stopper position

2 - 4

Adjustment

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4. Adjustment of the Needle Sidewise Movement (Needle Swing Timing)• When the needle sidewise movement move from the left base line to the right base line, the needle tip should

be 4.0 to 6.0mm from the fase of the needle plate. 1 Turn the selection dial to [3].2 Turn the dial to [5] to maximize the zigzag width. 3 Loosen the two screws (set screw, socket (FT), size 4M x 4) securing the worm pulley.4 Rotate the worm pulley, and adjust the position.5 Tighten the two screws (set screw, socket (FT), size 4M x 4) to secure the worm pulley.6 Turn the pulley to verify that needle swing timing is within the criteria.

Set screw, socket (FT) M4 × 4Worm pulley

2 - 5

Adjustment

5. Adjust of the down position back and forth for the presser foot1 Turn the selection dial to [3].2 Turn the pulley to adjust height of the to needle the top face of the zigzag presser foot.3 Adjust that to tarn the needle holder shaft of the needle unit with the flat-blade screwdriver so that the down

position back and forth to the needle hole of the zigzag presser foot in going on the center.4 Check the down position back and forth to the needle hole of the zigzag presser foot on the needle is the

uppermost position.* Check the gap between the needle and the zigzag presser foot (front and back) to 0.1 mm or more in both

front and back.

Needle hole

Needle holder shaft

Position of needlepoint

2 - 6

Adjustment

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6. Adjustment of the Needle Swing• When the Z dial is turned from 0 to 5 while the needle is at the right down position with the maximum zigzag

width setting, variation in needle down should be within 0.15 mm. 1 Turn the selection dial to [3].2 Turn the dial to [5] to maximize 3 Turn the pulley to lower the needle bar until the needle tip is level with the top face of the needle plate when

the needle is at the right down position.4 Loosen the screw at the Z adjustment nut. 5 Adjust the position of the needle with the Z adjustment nut so that the needle tip does not move when the Z

dial is turned from 5 to 0. 6 Tighten the screw.7 Turn the Z dial from 0 to 5 and 5 to 0 to verify that variation in needle down is within the criteria.

2 - 7

Adjustment

7. Adjust of the down position of the straight line on the left base line (right / left)1 Turn the Z dial to [5] to maximize the zigzag width.2 Turn the pulley to adjust height of the needle to the top face of the needle plate on the left base line.3 Compare the left and right gap [2] and [3] of the down position with the selection dial.4 Loosen the screw, pan (S/P washer) M3 x 8 of the selecting unit assy.5 Adjust the adjusting nut of the selecting unit with the wrench so that the down position of the straight line on

the left base line and the down position of the Z on the left base line is approximately same.6 Tighten the screw, pan (S/P washer) M3 x 8 of the selecting unit assy.7 Check the left and right gap of the down position of the straight line on the left base line for the down

position on the left base line.* The gap should be 0.15 mm or less.

Needle hole

0.15 mm or less

Dial [3]

Dial [2]

Adjusting nut

2 - 8

Adjustment

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8. Adjustment of the down position of the bar track (BH “ac”) on the leftbase line (right / left)• The left and right gap of the down position of the bar track on the left base line should be 0.2 mm or less.

1 Turn the selection dial to [1].2 Turn the Z dial to [5] to maximize the zigzag width.3 Draw the BH lever to the bottom, and push the BH lever to the back side.4 Remove the presser foot from the presser foot holder.5 Turn the pulley unit the bar track down position to adjust height of the needle to the top face of the needle

plate on the left base line.6 Loosen the screw, pan (S/P washer) M3 x 6 of the selecting unit assy.7 Adjust the BHZ adjust plate of the selecting unit with flat-blade screwdriver (small) so that the down

position of the bar track on the left base line and the down position of the Z on the left base line isapproximately same.

8 Tighten the screw, pan (S/P washer) M3 x 6 of the selecting unit assy.

BH Z adjusting plate Screw, pan (S/P washer) M3 x 6

2 - 9

Adjustment

9. Adjustment of the Needle Bar Height• When the rotary hook point is even with the perimeter of the needle (#14) after turning the pulley by hand

from the zigzag maximum left needle down position, the distance from the highest point of the needle hole tothe lower edge of the rotary hook point should be 1.0 to 1.4 mm.

1 Select the maximum zigzag width.2 Turn the pulley until the perimeter of the needle is even with the rotary hook point near the left needle drop

position.3 Loosen the screw (Set screw, socket, FT, M 4 × 4) on the needle bar clamp.4 Adjust the needle bar height until the distance between the highest point of the needle hole and the lower

edge of the rotary hook point is 1.0 to 1.4 mm.5 Tighten the screw (set screw, socket, FT, M 4 × 4) on the needle bar clamp.

Set screw, socket (FT) M4 × 4

Needle bar

1.0 - 1.4mm

Right edge of needle and tip coincide

2 - 10

Adjustment

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10.Clearance between the needle and the rotary hook point adjustment1 Turn the Z dial to [5] to maximize the zigzag width.2 Turn the selection dial to [3].3 Turn the pulley, and then stop the outer rotary hook tip at the back side position of the needle on the left base

line.4 Loosen the screw bind M3 x 25 of the needle presser module.5 Turn the adjusting screw with the wrench, and adjust the gap between the needle and the outer rotary hook

tip.6 Tighten the screw bind M3 x 25 of the needle presser module.7 Check the gap between the needle and the outer rotary hook tip.

* Iron-sintering outer rotary : The gap should be 0.25 mm or less, and without contact.* Plastic outer rotary : The gap should be 0.1 to 0.3 mm.

Adjusting screw

2 - 11

Adjustment

11.Adjustment of the Position of the Inner Rotary Hook Rotation PreventionBracket1 Set the inner rotary hook in the rotary hook.2 Loosen the bind screw securing the inner rotary hook rotation prevention bracket assy.3 Adjust the position of the inner rotary hook rotation prevention bracket assy. so that the overlap distance

between the inner rotary hook and the rotation prevention bracket assy. is 2.4 to 2.7 mm and secure it withthe screw, pan (S/P washer ) M 3 × 6.

2.4 - 2.7mm

Screw, pan (S/P washer) M3 × 6

2 - 12

Adjustment

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12.Adjustment of the Upper Thread Tension• The thread tension should be 0.38 - 0.43 N (38 - 43g) when pulled slowly using a tension gauge.

1 Raise the presser foot.2 Set the thread tension dial to 4.3 Thread a schappe spun sewing thread # 60 through the thread guide and the thread tension disc.4 Lower the presser lifter.5 Adjust the tightening amount of the thread tension adjusting screw so that the thread tension is 0.38 - 0.43 N

(38 - 43g) when pulled slowly using a tension gauge.6 Apply a small amount of screw locking agent to the thread tension adjusting screw.

0.38 - 0.43N (38 - 43g) Adjusting screw

2 - 13

Adjustment

13.Adjustment of the Inner Rotary Hook (Lower Thread) Tension1 Set a bobbin (wound with a schappe spun sewing thread # 60) in the inner rotary hook and put a thread

through.2 Adjust the tightening amount of the spring tension adjusting screw so that the thread tension is 0.10 to 0.12 N

(10 to 12 g) when pulled slowly using a tension gauge.

0.1 - 0.12N(10 - 12g)

Shapesupan thread #60

Spring adjusting screws

2 - 14

Adjustment

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14.Adjustment of the Thread Winding (Uneven Bobbin Winding and Amount of Thread Winding)1 Move the thread winding guide assy. up or down to adjust and correct for uneven bobbin winding. (Uneven

bobbin winding)2 Rotate the bobbin presser to adjust the amount of thread winding. (As a guideline of thread winding amount,

a bobbin should be wound up to 80 to 90% of the external diameter of the bobbin.)

80 - 90%

2 - 15

Adjustment

15.Adjustment of the feed of the bar track (BH “a”).• The feed of the bar track should be 0 to 0.1 mm.

1 Turn the selection dial to [1].2 Turn the Z dial to [5] to maximize the zigzag width.3 Draw the BH lever to the bottom.4 Switch on the sewing machine, and step on the foot controller and then stop it after drive the sewing machine

for a while.5 Push the BH lever to the back side.6 Turn the pulley until the bar track down position.7 Attach the presser foot to the presser fool holder.8 Set the broad cloth, and take down the presser foot.9 Loosen the screw, pan (S/P washer) M3 x 6 of the selecting unit assy.< Adjust the BHF adjusting plate A assy. with flat-blade screwdriver (small) so that the feed should be 0 to

0.1mm at the bar track BH “a”.A Tighten the screw, pan (S/P washer) M3 x 6 of the selecting unit assy.

Screw, pan (S/P washer) M3 x 6 BH F adjusting plate A assy.

2 - 16

Adjustment

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16.Adjustment of the feed• The feed should be 4.5 to 5.5mm when 11 stitches are sewn is feed [F] mode.

1 Turn the selection dial to [3].2 Turn the feed dial to [F].3 Loosen the screw bird M4 x 14 of feed connecting lever A.4 Move the feed adjusting shaft back and forth to roughly adjust the feed to be with the criteria.5 Tighten the screw bind M4 x 14 of the feed connecting lever A.6 Fine-tune the feed with the adjustment screw.

Adjusting screw Screw bind M4 x14

11P

: 4.

5 to

5.5

mm

Feed adjusting shaft

2 - 17

Adjustment

17.Adjustment of the feed• The feed should be 4.5 to 5.5 mm when 11 stitches are sewn in feed [F] mode

1 Turn the selection dial to [3].2 Turn the feed dial to [F].3 Loosen the binding screw of feed transmission lever A.4 Move the axis back and forth to roughly adjust the feed to be within the criteria. 5 Tighten the feed transmission lever screw.6 Fine-tune the feed with the adjustment screw.*Key point

• After adjusting the feed, be sure to check the feed for the super stitch 1 pattern and super stitch 2 pattern. If the feed needs adjusting, follow the descriptions in sections 12 and 13.

Fine-tune the feed with the adjustment screw (6)

Binding screw (3)

2 - 18

Adjustment

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18.Adjustment of the feed of the left over edging button hole (BH ”b”)• The number of needles should be +10 to -4 for right over edging, when that sewed 20 mm with the left over

edging for BH.1 Turn the selection dial to [1].2 Turn the Z dial to [5] to maximize the zigzag width.3 Turn the feed dial to [F].4 Sandwich the button more than a diameter of 20 mm to the BH foot, and attach the BH foot to the presser

foot holder.5 Repeat two pieces of broadcloth and sew it, and then check the number of the BH right over edging is 35 to

50 / 20 mm.6 Draw the BH lever to the bottom, and push the BH lever to the back side.7 Loosen the screw, pan (S/P washer) M3 x 6 of the selecting unit assy.8 Repeat two pieces of broadcloth and sew it for BH, and align the BHF adjusting plate B assy. with flat-blade

screwdriver (small) so that fine-tune the gap of the number of the needles at the left over edging and the rightover edging for BH.

9 Tighten the screw, -pan (S/P washer) M3 x 6 of the selecting unit assy.

Screw, pan (S/P washer) M3 x 6

BH F adjusting plate B assy.

2 - 19

Adjustment

19.Adjustment of the BH length• The inside dimensions of “a” and “c” should be 21 to 23mm for the button of a diameter of 20mm.

1 Turn the electing dial to [1].2 Turn the Z dial to [5] to maximize the zigzag width.3 Turn the feed dial to [F].4 Sandwich the button more than a diameter of 20 mm to the BH foot, and attach the BH foot to he presser foot

holder.5 Draw the BH lever to the bottom, and push the BH lever to the back side.6 Repeat two pieces of broadcloth and sew it for BH.7 Measure the inside dimensions of the BH “a” and “c”.8 Insert the hexagonal driver into the hole of the cover upper part, and then loosen the set screw socket (CP)

M4 x 4 of the BH change arm assy.9 Adjust the BH length by moving the BH lever front or back.

* Shorten length : Adjust the BH lever to the back side* Lengthen length : Adjust the BH lever to the front side

0 Insert the hexagonal driver into the set screw socket (CP) M4 x 4 of the BH change arm assy. and then attachit while pull over to the lower side.

A Check the inside dimensions of “a” and “c” for the button of a diameter of 20mm.* The inside dimensions should 21 to 23mm.

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LongerShoter

XL2600i/XL3500i/XL3600/BM3600/XL375010A06HF885S28/S29

service manual brother xl3750

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