Brother International DB2-B791 Service Manual

Brother International DB2-B791 Manual

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  • Brother International DB2-B791 | Service Manual - Page 1
    SERVICE MANUAL FOR DB2-B791 DB2-B7910 HIGH SPEED SINGLE NEEDLE NEEDLE FEED LOCK STITCH MACHINE WITH AUTOMATIC THREAD TRIMMER OM gm "MUM 41/1. MO San SINS
  • Brother International DB2-B791 | Service Manual - Page 2
    Machine head 2 2. Knee lifter bell crank stopper 2 3. Belt 2 OPERATION 3 1. Lubrication 3 2. Pressure on materials 3 3. Needle 4 4. Threading 4 5. Stitch length 5 6. Thread tension 5 7. Sewing mechanism 13 5. Thread trimmer mechanism 15 6. Tension release 18 7. Thread
  • Brother International DB2-B791 | Service Manual - Page 3
    Rotary hook mechanism 28 4. Presser foot mechanism 29 5. Needle bar mechanism 29 6. Machine covers 30 ADJUSTMENT 31 1. Needle bar height 31 2. Rotary hook position 31 3. reflection sensor replacement (37910) 46 4. Synchronizers 48 GAUGE PART CODE 49 TROUBLESHOOTING GUIDE 53
  • Brother International DB2-B791 | Service Manual - Page 4
    • DB2-B791-413 • MADE IN JAPAN Inv i-I BROTHER INDUSTRIE LTD • DB2-B7910-423 • MADE IN JAPAN Specification Application Sewing speed Maximum stitch length i DB2-8791 Standard -013 -015 Medium materials Thick materials 4,500 spm 3,500 spm 4 mm 5 mm D82-B791 Thread trimmer -O13 -O 15
  • Brother International DB2-B791 | Service Manual - Page 5
    head CD • • • • • 0 Put the head hinges 0 into the holes of the bed and adjust them to the rubber hinge • of the table • . Place the machine head onto the head cushions 0 at the four corners. 2. Knee lifter bell crank stopper 3. Belt 0 • Approx. 2 mm Approx.1 mm • • Approx.13-16 mm
  • Brother International DB2-B791 | Service Manual - Page 6
    from the magnet @ and the oil pan. X Use the oil specified by BROTHER: Hi White 70. (4) After removing the face plate, adjust oil absorption by turning the oil regulating valve ©. (5) After tilting the machine head until it stops, adjust oil absorption by turning the oil adjusting screw
  • Brother International DB2-B791 | Service Manual - Page 7
    3. Needle 0 X 0 qa) 4a? q Long needle-groove Insert the needle 0 completely, making sure that the long groove of the needle is on the left. Tighten it with the screw @. X Use needle DB x #1. 4. Threading 1. Needle threading Raise the thread take-up to the highest position 0 9 3 Pow' 10 Pass
  • Brother International DB2-B791 | Service Manual - Page 8
    5. Stitch length • While pushing the reverse feed lever 0 halfway down, turn the dial ® until the desired number is aligned with the pin© at the top, and release the reverse feed lever 0. ).'< The larger the number is, the longer the stitch length is. • The reverse stitching device is an
  • Brother International DB2-B791 | Service Manual - Page 9
    brother 01 0 2 0 07 0 30 SET START PLY INPUT PROGRAMM 1:7 1:1 111 C 111 (Need N MAX "SPEED ow H Set the power switch 0 to ON. The indicator @ goes on. Sewing plate when sewing, set the needle position switch @ to UP. • When the correction switch @ is set ON, the machine sews a material in
  • Brother International DB2-B791 | Service Manual - Page 10
    kCS) 0 AB if. CORRECTION 1 + o AUTO _ 10 sLow i START TACK STITCHES 00 0 1. Pocket sewing Ply sensor (Thin part) (Thick part) B (1) Press the SET START key 0. Its indicator goes on. (2) Set the material (thin part of the body) under the presser foot and press the PLY SENSOR key 61. Its
  • Brother International DB2-B791 | Service Manual - Page 11
    0. Its indicator blinks, then goes on. (3) Set a name tag (thick part of the body) under the presser foot and press the PLY SENSOR key 0. the temporary stop of the machine at position B). (9) Press the MARGIN key O. (10) Set the margin-to-seam width. (11) After sewing to material edge position C
  • Brother International DB2-B791 | Service Manual - Page 12
    the level feed connecting rod 0 is attached to the level feed link 0 and level feed arm link 0. The level feed link 0, whose one end is supported by the feed regulator S, swings back and forth. (3) The horizontal motion of the level feed arm link swings the level feed arm 0 back and forth
  • Brother International DB2-B791 | Service Manual - Page 13
    3. Feed regulation mechanism OO 0 0 (1) Turning the feed regulating dial 0 changes the inclination of the feed regulator 0. (2) Because the feed regulator is attached to the feed regulator assembly by the feed regulator connecting lever ©, the inclination of the feed regulator assembly 0 can be
  • Brother International DB2-B791 | Service Manual - Page 14
    4. Lubrication mechanism 1. Upper shaft lubrication 1, Oil cap Upper shaft se) e (1) Oil fed by the pump 0 enters the upper shaft from the upper shaft bushing M to lubricate upper shaft bushings L and R O. (2) The oil regulating valve is provided on the left end of the upper shaft to lubricate
  • Brother International DB2-B791 | Service Manual - Page 15
    2. Lower shaft lubrication I) Lower shaft Arm channel 0 • Y.-n At- 0 a) Lower shaft (1) Oil fed by the pump 0 lubricates the lower shaft and the lower shaft bushing L 0. (2) Some of the oil at the lower shaft bushing L flows through the lower shaft to lubricate the rotary hook. Oil shed from
  • Brother International DB2-B791 | Service Manual - Page 16
    the thread trimming cam lever assembly 0, secured by the thread trimming cam lever stud el, is pushed above the circumference of the thread trimming clutch O. - 15 -
  • Brother International DB2-B791 | Service Manual - Page 17
    (3) Movable knife holder action 10 0 a • 0 5mm 0. By the rotation of the lower shaft, the thread trimming clutch 0 pushes the slide block up. The motion of the slide block is transmitted to the forked shaft O via the thread trimming cam lever assembly The motion is then relayed to the thread
  • Brother International DB2-B791 | Service Manual - Page 18
    3. Needle and bobbin threads trimming 0 (1) When the needle rises 2 mm (2.2 mm with thick materials) above from its lowest position, the rotary hook point catches the loop formed by the needle. (2) When the thread trimming signal is turned on, the thread trimming clutch drives the movable knife.
  • Brother International DB2-B791 | Service Manual - Page 19
    6. Tension release O O 0 (1) The thread trimming solenoid operates when the thread trimming signal is turned on. (2) The solenoid lever@, attached to the end of the thread trimming solenoid 0, pushes the tension releasing lever 0. (3) The tension release wire 0 relays the motion of tension
  • Brother International DB2-B791 | Service Manual - Page 20
    rod lifting link G. pushes up the knee lifter complying bar via the presser foot (3) The knee lifter complying bar moves up the presser bar guide bracket 0 via the knee lifter bar 0, the knee lifter lever 0, the knee lifter connector and the knee lifter lifting lever 0. (4) The presser bar m and
  • Brother International DB2-B791 | Service Manual - Page 21
    and . (2) Set the needle bar 0 at the lowest position by turning the machine pulley. Loosen the screw 0 of the needle bar clamp 0 and remove the needle bar upward. (3) Remove the two screws O and the needle bar bracket guide 0. (4) Loosen the screws ® and 0. Remove the stud 0, the needle feed
  • Brother International DB2-B791 | Service Manual - Page 22
    guideO and the presser spring 0. (4) Loosen the screw CI and remove the presser bar from the presser bar guide bracket 0. co 0 0 4. Rotary hook mechanism (1) Tilt the machine head until it stops. (2) Remove the screwO and the bobbin case holder position bracket 0. (3) Loosen the three screws
  • Brother International DB2-B791 | Service Manual - Page 23
    5. Thread trimmer mechanism 0 IA 0 @ OM Reflection holder 0 00 Reflection sensor 000 (1) Remove the screw 0 and the fixed knife ®. (2) Press the thread trimming rod ® in the direction of the arrow until the two screws 0 are visible. (3) Remove the screws 0 and the movable knife ®. (4) Remove the
  • Brother International DB2-B791 | Service Manual - Page 24
    6. Feed mechanism CI 0 OD 0 © 0® , 6 O a) 0 Fig A 0 0 (1) Loosen the nut 0 and remove the stud screw 0. (2) Remove the wick from the feed lifting rock shaft 0. (3) Loosen the two screws @ and remove the set collar O. (4) Loosen the screw ® securing the feed lifting crank O. Loosen the screw ®of
  • Brother International DB2-B791 | Service Manual - Page 25
    extend 0.8 mm (subclass -3) or 1.2 mm (subclass -5) above the needle plate upper surface by loosening the screw O. (13) Maximize the feed per stroke, and turn the machine pulley. ®. (14) Adjust the feed dog so that it is centered both left-right and front-back of the groove of the needle plate by
  • Brother International DB2-B791 | Service Manual - Page 26
    [Wick insertion] cv (1) Remove the oil cap &from the horizontal feed shaft ®. (2) Insert the wick Qlinto the horizontal feed shaft O until one end of the wick m aligns with the end face of the horizontal feed shaft ®. (3) Attach the oil cap 0. (4) Put the oil cap of the horizontal feed bracket
  • Brother International DB2-B791 | Service Manual - Page 27
    2. Thread trimmer mechanism 0O0 0 CD 0 0 r I!I-I-j ® 2 3 9 4 00.0 Ir-G- 0 I L _ Qs) .I a 0 690060 €1). 0 0 (1) Remove the needle plate. (2) Place the collar 0 on the forked shaft and the forked shaft bushing. (3) Place the collar 0, the thread trimming cam lever spring @, the thread trimming
  • Brother International DB2-B791 | Service Manual - Page 28
    relayed es- Forward feed direction (g) When the thread is trimmed During operation 0.5 mm 0.6-0 8 mm O 0 CD, 6:5 1. Thread trimming clutch position Turn the machine pulley until the needle bar is raised 5 mm above from its lowest position. At this time, press the thread trimming solenoid 0 by
  • Brother International DB2-B791 | Service Manual - Page 29
    bracket with the screw ®. (3) Place the needle bar thread guide ®and secure the needle 0 with the screw ®. (4) its lowest position by turning the machine pulley (2.2 mm when sewing thick materials). At this time, the screw ®of the wheel O. X In model DB2-B7910, install the needle plate in (5) after
  • Brother International DB2-B791 | Service Manual - Page 30
    needle feed arm and the needle feed link © through the stud O to the needle bar bracket 0 with the screws 0 and O. (3) Secure the needle bar bracket guide ©with the two screws O. (4) Insert the needle bar fD into the needle bar clamp 0 from above the arm, and fasten the screw ID. (5) Install the
  • Brother International DB2-B791 | Service Manual - Page 31
    6. Machine covers 0 O • • a0 o (1) Secure the needle plate 0 with the two screws ED. Install the slide plate @. (2) Secure the upper tension regulator 0 with the screw O. (3) Secure the
  • Brother International DB2-B791 | Service Manual - Page 32
    line ----- D BX1 D A X 1 2mm Align the bottom reference line of the needle bar @with surface A of the needle bar oil rejector cover @ by turning the machine pulley slowly. At this time, make sure that the rotary hook point ©aligns with the needle center 0, and that the gap between the top edge
  • Brother International DB2-B791 | Service Manual - Page 33
    3. Feed timing For medium materials For thick materials 5 mm L (1) Turn the machine pulley Otoward the machine front until the feed dog 10 descends and the tips of the feed dog 0 align with the upper surface of the needle plate 0. At this
  • Brother International DB2-B791 | Service Manual - Page 34
    4. Feed dog height and angle ©J l [Feed dog height] (1) The feed dog height when the feed dog 0 is fully raised is 0.8 mm for thin and medium materials, and 1.2 mm for thick materials. (2) To adjust the feed dog height, loosen the screw @when the feed dog 0 is fully raised, and then rotate the
  • Brother International DB2-B791 | Service Manual - Page 35
    section Chamfering Chamfering Washer O Snap ring Forward and reverse feed stitch length are adjusted together. (1) Set the feed regulating dial 0 to mark 3. (2) Sew 11 stitches forward and reverse at the inching speed (215 spm). (3) Adjust as follows when the forward and reverse feed stitch lengths
  • Brother International DB2-B791 | Service Manual - Page 36
    the thread trimming signal. When turning on the power and then stopping the machine in down needle stop position, there should be a 18-22 mm gap surface and the bottom edge of the needle set screw. When stopping the machine in up needle stop position, there should be 9.5-11.5 mm gap between the
  • Brother International DB2-B791 | Service Manual - Page 37
    Movable knife removal O xra 0 • (1) Raise the presser foot using the presser bar lifter. (2) Remove the screw ©and the needle plate O. (3) Turn the machine pulley until the needle bar reaches its highest position. (4) Press the thread trimming rod 0 by hand in the direction of the arrow until the
  • Brother International DB2-B791 | Service Manual - Page 38
    8. Servo solenoid adjustment 0 O 0 0.5-0.6 mm OD 0 O 0 ®I I 0 0 0 O (1) Set the feed regulating dial 0 to its maximum. (2) Remove the oil cap 0. (3) After loosening the screw @from the oil cap @ hole using a hexagon wrench, adjust the gap between the reverse link lever assembly O and the reverse
  • Brother International DB2-B791 | Service Manual - Page 39
    NO. CITY. SELECT +0.5 1 2mm Grease O 0 - Smaller (7. Ir34/- 0 Bigger 0 0 0 1 When PROGRAMME key No.2 is pressed while indicators No.1, 2, 6 and 7 are off (normal sewing mode), the pitch is indicated on the display. 2 Make sure the actual pitch is the same as the indicated one (the actual
  • Brother International DB2-B791 | Service Manual - Page 40
    10. Spring installation (B7910) o x The spring 0 absorbs the vibration sound produced by the servo solenoid. Install as in the figure above. 11. Feed mechanism weight check (B7910) 0 0 0 0 a CD co 0 0 0 Raise the presser foot and then set the feed regulating dial to its maximum. Check that
  • Brother International DB2-B791 | Service Manual - Page 41
    whose distance to the needle hole is 18 mm. The other is for sensors whose distance to the needle hole is 25mm. [Installation] (1) Tilt the machine head until it stops. (2) Move the plate (R) 0 in the direction of the arrow by loosening the screw 0. (3) Put the plate (M) into the sensor hole in
  • Brother International DB2-B791 | Service Manual - Page 42
    the needle plate, adjust the gap between the upper surface needle plate 0 and the bottom of the sensor guard 0 to 0.5-1 mm, using the screw 0. The machine may not stop if fingers are put in the sensor. -41 -
  • Brother International DB2-B791 | Service Manual - Page 43
    indicated number on the display, if the sensor position is changed. The machine does not stop at a material edge without this adjustment. The distance is . 18mm Distance indication 2.0mm 25 mm 2.0 mm =.
  • Brother International DB2-B791 | Service Manual - Page 44
    removal. 1. Thread trimming solenoid / 6 11121314 4r/ I ©© (1) Disconnect the terminal pin (male) from pins 4 and 5 of the nylon connector 12P. (2) Tilt the machine head until it stops. 0000 (3) Loosen the screw 0. Disconnect the cord from the cord holder ®. (4) Remove the cord from the cord
  • Brother International DB2-B791 | Service Manual - Page 45
    3. Thread wiper solenoid, thread wiper switch O C) o 0 6 O 0 (1) Disconnect the terminal pin (male) from pins 7 and 8 of the nylon connector UP. (2) Remove the cords from the three cord holders by loosening the three screws 0. (3) Remove the solenoid cover 0 by removing the screw 0. (4) Remove
  • Brother International DB2-B791 | Service Manual - Page 46
    2. Thread wiper (I) 0 0 e Thread wiper position 0 5mm • 00 4 No.7 rI! No.8 `, [Installation] (1) Secure the solenoid setting plate 0 on the side of the face plate el with the screw e. (2) Secure the thread wiper solenoid assembly 0 and the solenoid setting bracket ® to the solenoid setting
  • Brother International DB2-B791 | Service Manual - Page 47
    3. Photo-cell and reflection sensor replacement (87910) 45.8 mm 18 mm 04.2 mm 25 mm X Do not damage the cover Co when removing the needle plate e. X Drill a sensor hole with a diameter of 4.2 mm on a needle plate that is available on the market. The distance between the needle hole and the sensor
  • Brother International DB2-B791 | Service Manual - Page 48
    70.8 10.6 11.7 4.5 18.5 17 7 14.7 9.8 AMIN 143855-001 S 03357-001 35 26 1.5 10 las 10.8 10.4 1 19 18 7 14.7 9.8 159525-001 35 11.25 1.15 148842-001 9.6 11 10.6 9.9 8.5 19 18 7 14.7 9.8 159526-001 35 26.4 11.2 9.6 11 7 14.7 9.8 S 13101-001 S 13102-001 35 26 12 10 13.1 10.6 12
  • Brother International DB2-B791 | Service Manual - Page 49
    10.8■ 25 19 18 S 11157-001 10.8 =1 5.6 is • 7 6 S 11159-001 10 6 159521-001 35 26 ... 11.5 10 10.6 10.41 \ 11 •.) ...7..... L14.7 9.8 1,15 140717-001 35.2 11 „ Mthieck materials 10.8 .1 Ll C:=3 sue 0- 10.6 4.5 25 18.5_. 17 ilittM S 11463-001 10.8 18 19 14 S 11158-001
  • Brother International DB2-B791 | Service Manual - Page 50
    TROUBLESHOOTING GUIDE 1. Machine head Problem Cause Improper needle installation Bent needle. Blunt needle tip, jammed eye. Check Needle facing, height Needle Solution Reinstall needle. Page z Replace needle. Needle breakage Improper
  • Brother International DB2-B791 | Service Manual - Page 51
    Problem Cause Check Solution Page Thread breaks frays Burr in thread path --I Blunt needle tip Remove with sandpaper. Replace needle. 4 Improper needle Needle facing, installation - height
  • Brother International DB2-B791 | Service Manual - Page 52
    Problem Cause Check Solution Page Needle thread does not tighten. 4Insufficient needle thread tension r Excessive needle thread tension Bobbin thread does not tighten. _tExcessive needle thread
  • Brother International DB2-B791 | Service Manual - Page 53
    Problem Cause Check Solution Page _1Tension disc does not open sufficiently. Needle thread escapes at sewing start. Excessive . Replace thread cutter solenoid. / Check circuits. Refer to motor adjustment manual. Adjust pretension. 5 / Replace with presser foot have back channel.
  • Brother International DB2-B791 | Service Manual - Page 54
    Problem Cause Check Solution Page dImproper thread wiper facing Thread wiper does not wipe thread. Thread wiper strikes needle HThread wiper does not operate. 1Thread wiper
  • Brother International DB2-B791 | Service Manual - Page 55
    BROTHER INDUSTRIES, LTD. HEAD OFFICE: No. 35, 9-CHOME, HORITA-DORI, MIZUHO-KU, NAGOYA, JAPAN 467 CABLE: BROTHER NAGOYA TELEX: BROTHER 4473696J & J59743 117-791.7910 18090320 BC) Printed in Japan
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SERVICE
MANUAL
FOR
DB2-B791
DB2-B7910
HIGH
SPEED
SINGLE
NEEDLE
NEEDLE
FEED
LOCK
STITCH
MACHINE
WITH
AUTOMATIC
THREAD
TRIMMER
OM
gm
"MUM
41/1.
MO
San
SINS