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28. ADJUSTMENT OF REVERSE SEWING SWITCH (B341

⋅

B349

⋅

B351

⋅

B352)

STANDARD

The clearance between the BT switch and the reverse sewing lever B should be 1.0 ~ 1.5 mm.

ADJUSTMENT

1. Loosen the screw for BT switch holder slightly.
2. Use a standard screwdriver to move the top of the BT switch and adjust the clearance between the BT

switch and the reverse sewing lever B.

3. Tighten the screw.

Note

Check that the BT switch turns on when the reverse sewing button is pressed and the stitch length dial is set
to "0".

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Summary of Contents for BL6200

Page 1: ...4 1998 ...

Page 2: ...es company for such changes Brother industries Ltd Nagoya Japan CONTENTS I PRINCIPAL MECHANISMS 1 II TROUBLES AND CHECK POINTS 11 III HOW TO ADJUST THE ELEMENTS 21 IV HOW TO CHANGE THE PARTS 58 1 Always use rubber gloves when handling a printed circuit board and do not touch the metal portion of the printed circuit board with bare hands 2 Keep the human body earthed to avoid generating static elec...

Page 3: ...L CHART B338 B346 B347 B348 2 1 MECHANICAL CHART B341 B349 B351 B352 3 2 POWER TRANSMISSION CHART 4 3 DISPLAY SYSTEM BY MICRO COMPUTER 8 3 DISPLAY SYSTEM BY MICRO COMPUTER 9 4 MAIN MOTOR CONTROLLED BY MICRO COMPUTER 10 ...

Page 4: ... 2 1 MECHANICAL CHART B338 B346 B347 B348 This part is not installed on the B346 since it is a 4 step BH model ...

Page 5: ... 3 1 MECHANICAL CHART B341 B349 B351 B352 These parts are not installed on the B341 B351 and B352 since they are LCD models ...

Page 6: ...d take up lever and zigzag movements B338 B346 B347 B348 Thread take up lever Eccentric counter weight Upper shaft Pulley Needle bar crank rod Needle bar clamp Needle bar Needle bar supporter Needle Selecting cam Pattern cam Worm gear Z finger Zigzag connecting rod assembly ...

Page 7: ...r and zigzag movements B341 B349 B351 B352 Thread take up lever Eccentric counter weight Worm gear Pulley Needle bar crank rod Needle bar clamp Needle bar Needle bar supporter Needle Pattern cam Zigzag connecting rod assembly Z finger Selecting cam Upper shaft ...

Page 8: ... shaft gear Outer rotary hook assembly Feed dog Feed bar Vertical feed cam Drop lever Horizontal feed plate Rotary shatter Feed pattern cam Feed finger Feed regulator Horizontal feed shaft Horizontal feed cam Forked connecting rod Horizontal feed arm Lower shaft Timing belt Timing pulley D Worm gear Pulley Motor belt Motor ...

Page 9: ... 7 C Automatic 1 step BH mechanism B338 B341 B347 B348 B349 B351 B352 BH change shaft BH change arm BH stopper BH cam BHF finger assembly BH Iever BH foot Feed control cam BH BHF finger assembly 2 A 2 B ...

Page 10: ...gulates the LCD controller driver which controls the information shown on the display 1 LINE DISPLAY SYSTEM BLOCK CHART Power supply circuit and motor control circuit LCD panel LCD controller driver SED1278 8 bit MCU M38004M8 Contrast volume Message key Pattern sensor BH Iever SW Bobbin winder SW Motor control P C board LCD unit ...

Page 11: ...ontrols the information shown on the display 4 LINE DISPLAY SYSTEM BLOCK CHART LCD panel LCD controller driver NJU6426F LCD segment driver NJU6417F Power supply circuit and motor control circuit Motor control P C board LCD unit Pattern sensor BH Iever SW Bobbin winder SW 8 bit MCU M38002SFP ROM HN62302BF EEPROM X24C00P Contrast volume A B keys LCD control P C board ...

Page 12: ... the machine easy to use it should take into account that the machine should run slowly when it starts and the needle should be in the up position when it stops To execute these requirements the main motors of these sewing machines are controlled by a micro computer MOTOR CONTROL BLOCK CHART Drive circuit Speed sensor SS Switch Reverse sw Bobbin winder sw CPU Reset circuit Speed volume Foot contro...

Page 13: ... 14 17 No characters appear on the LCD 15 18 The message keys do not work 15 19 The LCD contrast cannot be adjusted 15 20 The wrong pattern name appears on the LCD 15 21 The Bobbin Winding message continues to appear on the LCD 16 22 The Bobbin Winding message does not appear on the LCD when the machine is set for bobbin winding 1 line LCD 16 23 Message Bobbin Winding Selected does not appear when...

Page 14: ...achine operates cannot be adjusted 19 32 The needle does not stop in the up position 19 33 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 19 34 The machine stops immediately after bobbin winding is started 20 35 The machine does not operate when the foot controller is depressed 20 ...

Page 15: ...er threading Thread correctly 5 Upper thread breaks during sewing 1 Bent or blunt needle 2 Improper setting of needle 3 Thread tension is too tight 4 Thread is tangled 5 Inferior needle eye 6 Inferior needle slot of needle plate 7 Inferior upper thread path 8 Inferior thread 9 Needle hits needle plate or outer rotary hook 10 There are scratches on inner rotary hook Change the needle Set the needle...

Page 16: ...stment Adjust screw Refer to P 42 12 Improper buttonhole size against button size 1 Improper adjustment of buttonhole length Adjust the length of buttonhole Refer to P 44 13 Unbalanced patterns 1 Stitch length dial is not set at 4 2 Feed dog is worn out 3 Improper height of feed dog 4 Improper attachment of feed dog 5 Forward and reverse feedings differ 6 Stitch width dial is not set to 5 Operate ...

Page 17: ...e LCD do not work 1 Message key top does not work 2 Inferior LCD unit Check the message key and key top Replace the LCD unit 4 line LCD A B 4 line LCD A B 1 Each key tops do not work 2 Inferior LCD control PCB Check each keys and key tops Replace the LCD control PCB 19 The LCD contrast 1 line LCD 1 line LCD cannot be adjusted 1 LCD contrast key does not work 2 Improper LCD contrast Check the slide...

Page 18: ...ction of connector CN5 on Motor control unit 3 BW switch does not work 4 Inferior BW switch 5 Inferior LCD control PCB Connect the P1 on LCD control PCB Connect the CN5 on Motor control unit Adjust the BW switch Refer to P 51 Replace the BW switch Refer to P 51 Replace the LCD control PCB 24 Message Lower BH Lever does not appear when buttonhole is set and buttonhole lever is not lowered 1 line LC...

Page 19: ...00 V AC when the AC cord is inserted 2 The resistance on both ends of the power switch is not less than 1 Ω when the power is turned on 3 The fuse is broken 4 The light does not turn on The light may be damaged or deteriorating or it may have a bad connection Remove the light and measure the resistance on both ends It should be less than 3 Ω 5 The output from the transformer is incorrect When conn...

Page 20: ... run smoothly or it does not run at a high speed 1 The Pulley is sometimes easy or sometimes difficult to move when it is rotated by hand 2 Accumulated lint or thread under the needle plate 3 Improper tension in motor belt and timing belt 4 Tight gearing of the pattern cam gear and worm gear 5 The rotary shutter is dirty 6 The motor control unit is installed incorrectly It is loose or slanted 7 Th...

Page 21: ...ted 3 Inferior BW switch The resistance between pins 1 and 2 of connector CN5 black should be less than 1Ω when the BW switch is turned on and when the BW switch is turned off 4 Other causes Check and adjust if necessary Refer to P 48 Install the motor control unit correctly Replace the BW switch Refer to P 51 Replace the motor control unit 33 The machine does not operate if the reverse sewing but...

Page 22: ...Refer to P 51 Replace the motor control unit 35 The machine does not operate when the foot controller is de pressed 1 The foot controller is not operating properly The resistance between the two ends of the foot controller plug is not less than 10 KΩ 2 The resistance between pins 2 and 3 of the pin jack assembly on the PCB F C should be less than 1 Ω when the foot controller is plugged in and when...

Page 23: ...18 FORWARD AND REVERSE SEWING FOR RICK RACK STITCH 40 19 ADJUSTMENT OF FEED 41 20 BUTTONHOLE ADJUSTMENT FORWARD AND REVERSE FEEDING 42 21 BUTTONHOLE ADJUSTMENT BAR TACK FEEDING 43 22 BUTTONHOLE ADJUSTMENT THE LENGTH OF THE BUTTONHOLE AND THE PRESSURE OF THE BH LEVER 44 23 MAXIMUM STITCH WIDTH WHEN SET AT STRAIGHT LEFT AND ZIGZAG STITCH 45 24 FORWARD AND REVERSE FEEDING FOR STRAIGHT STITCH 46 25 AD...

Page 24: ... 22 1 ADJUSTMENT OF EACH CONTROL UNIT 4 STEP BH MODEL B346 ...

Page 25: ... 23 1 ADJUSTMENT OF EACH CONTROL UNIT 1 STEP BH MODEL B338 B341 B347 B348 B349 B351 B352 ...

Page 26: ...should be at its bottommost position Turn pulley counterclockwise ADJUSTMENT 1 Remove the timing belt from the horizontal feed cam the tension pulley and timing pulley D 2 Position the mark on the horizontal feed cam so it is at its topmost position and the mark on timing pulley D so it is at its bottommost position 3 Install the timing belt onto the horizontal feed cam the tension pulley and timi...

Page 27: ... timing belt when the center of each belt is just pushed with about 200g pressure ADJUSTMENT 1 Loosen two screws on the motor holder 2 Adjust tension on timing belt by moving motor holder 3 Tighten two screws 4 Loosen the screw on tension pulley 5 Adjust tension on timing belt by moving tension pulley 6 Tighten the screw ...

Page 28: ...ttern dial to straight stitch and stitch length to 4 2 Loosen two screws on eccentric counter weight 3 Adjust the eccentric counter weight so the needle is at its highest point when the mark on the horizontal feed cam of the upper shaft is at its topmost position 4 Tighten two screws 5 Make sure that timing was adjusted correctly by turning the pulley counterclockwise 6 Loosen two screws of thread...

Page 29: ...gear lever fixing screw 3 Move the zigzag connecting rod to its lowest position where the roller of zigzag connecting rod contacts unit base F while keeping the zigzag width dial at the minimum 0 and while preventing backlash in the gear 4 Tighten the screw 5 Set zigzag width dial to 5 and set the right position of needle by turning the pulley 6 Turn zigzag width dial from 0 to 5 and adjust eccent...

Page 30: ...e between the hook and the needle should be less than 0 1 mm and the hook should not hit the needle ADJUSTMENT 1 Set pattern dial to zigzag stitch and zigzag width dial to 5 the needle is at the left side 2 Loosen three screws on lower shaft gear 3 Adjust position of rotary hook When needle raises from its lowest position by 2 75 3 15 mm the pointed end of rotary hook should meet with right side o...

Page 31: ...right side of the needle the clearance between the top of the needle eye and the hook point should be 0 8 1 2 mm ADJUSTMENT 1 Set pattern dial to zigzag stitch and zigzag width dial to 5 the needle is at the left side 2 Set position so that hook point meet with right side of the needle by turning the pulley 3 Loosen the screw on needle bar holder 4 Adjust height of needle clamp 5 Tighten the screw...

Page 32: ...topper should hold inner rotary hook by 1 9 2 1 mm as shown in drawing ADJUSTMENT 1 Loosen the screw on inner rotary hook stopper 2 Adjust the position of inner rotary hook stopper Face A on inner rotary hook and feed direction should be at right angles 3 Tighten the screw ...

Page 33: ...e the clearances between the feed dog and the needle plate should be 0 3 0 8 mm ADJUSTMENT 1 Loosen two screws on the horizontal feed plate 2 Adjust the left and right sides of the feed dog 3 Tighten two screws 4 Turn the pulley to move the feed dog to its initial feed position 5 Loosen the screw on the horizontal feed arm 6 Adjust the arm so the clearance between the feed dog and the needle plate...

Page 34: ... the feed dog is raised to its highest position ADJUSTMENT 1 Raise the feed dog using the drop lever then raise the feed dog to its highest position by turning the pulley 2 Loosen the screw for vertical feed finger 3 Adjust the height of the feed dog by turning vertical feed finger 4 Tighten the screw ...

Page 35: ...esser foot and needle plate should be 6 0 6 5 mm ADJUSTMENT 1 Raise presser foot 2 Loosen the screw on presser bar guide bracket 3 Adjust height of presser bar Presser foot should be parallel to feed dog 4 Tighten the screw B338 B346 B347 B348 B341 B349 B351 B352 ...

Page 36: ... thread tension using tension gauge and adjust tension to 10 13g by turning thread tension control screw 4 Tighten the screw B338 B346 B347 B348 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 Set thread tension dial to 4 put polyester thread between tension discs and lower presser foot 2 Loosen ...

Page 37: ...0 properly 2 Turn the pulley counterclockwise and adjust needle position at the top of needle eye 0 1 5 mm down from the surface of needle plate 3 Loosen the screw for roller adjusting shaft 4 Turn the roller adjusting shaft by screw driver and adjust the roller position in between lock and release condition with drawing thread Adjust the roller so it is within one cycle of the roller adjusting sh...

Page 38: ...ern dial to zigzag stitch and check baseline on selecting cam which should meet with upper end of release lever 2 Loosen two screws on indication gear 3 Set the symbol of zigzag stitch at the center of the indication window by turning indication gear 4 Tighten two screws NOTE After adjustment make sure each pattern is indicated at the center of the indication window by turning pattern dial ...

Page 39: ...inger is released clearance between cam finger and pattern cam feed cam should be 0 3 0 5 mm ADJUSTMENT 1 Set pattern dial to rick rack stitch and release cam finger from pattern and feed cam 2 Loosen the nut to release adjustment screw 3 Adjust clearance by turning release adjustment screw 4 Tighten the nut ...

Page 40: ...f feed cam finger and zigzag cam finger by turning pattern dial 2 Loosen the screw on selecting lever holder 3 Set the Z cam finger and F cam finger to the center position of each cam by adjust selecting lever holder 4 Tighten the screw 5 Make sure cam finger is located at the center position of each cam by turning pattern dial The shape of the cams on the B346 differ slightly ...

Page 41: ...eed gear feed cam and feed finger should meet in line ADJUSTMENT 1 Set stitch length dial to 0 2 Set the mark on the feed cam to feed finger 3 Set the mark on the feed gear to the mark on feed cam 4 Set the mark on the feed dial gear to the mark on feed gear 5 Fix the feed bracket by tightening two screws ...

Page 42: ...hen pattern dial is set to rick rack stitch there should be no difference between forward and reverse feed ADJUSTMENT 1 Set pattern dial to rick rack stitch 2 Loosen the nut for adjustment screw 3 Adjust forward and reverse feeding by turning screw 4 Tighten the nut ...

Page 43: ...o 0 stitch length should be 0 mm ADJUSTMENT 1 Set the pattern dial to the zigzag stitch the zigzag width dial to 5 and the stitch length dial to 0 2 Loosen the screw on feed dial gear 3 Turn feed dial gear slightly so that stitch length become 0 mm 4 Tighten the screw ...

Page 44: ...difference of sewing pitch between right and left rows 5 Loosen the nut for buttonhole feed adjusting screw 6 Adjust forward and reverse feeding by turning the screw 7 Tighten the nut 4 STEP BH MODEL B346 STANDARD When pattern is set to b and d there should be no feeding difference between left and right legs ADJUSTMENT 1 Set pattern dial to d 2 Set stitch length dial to F 3 Set BH adjusting eccen...

Page 45: ...Adjust the screw If forward feeding is obtained Turn screw counterclockwise If back feeding is obtained Turn screw clockwise 4 Tighten the nut 4 STEP BH MODEL B346 STANDARD The feeding of bar tack should be less than 1 0 mm 10 feedings ADJUSTMENT 1 Set pattern dial to ac 2 Loosen the nut for bar tack feeding adjusting screw 3 Adjust the screw If forward feeding is obtained Turn screw counterclockw...

Page 46: ...ed to pull the BH Lever forward should be 50 110 g ADJUSTMENT 1 Loosen the screw on BH change arm 2 Adjust the position of BH lever according to below drawings 3 Tighten the screw 4 Loosen the screw for the eccentric nut 5 Adjust eccentric nut so that the pressure needed to pull the BH Lever forward is 50 110 g The eccentric nut should not be rotated more than half a turn 6 Tighten the screw Adjus...

Page 47: ...2 Set pattern dial to zigzag stitch and set zigzag width dial to 5 the needle is at the left side 3 Drop the needle into the paper by turning the pulley 4 Set the pattern dial to the straight stitch and set zigzag width dial to 5 so the needle moves to the left 5 Drop the needle into the paper by turning the pulley 6 Loosen the nut of adjusting screw 7 Adjust left straight needle position by turni...

Page 48: ...t to 2 there should be no difference between forward and reverse feed ADJUSTMENT 1 Set pattern dial to straight stitch 2 Set stitch length dial to 2 3 Sew straight stitch on a piece of paper then sew reverse straight stitch by pushing reverse button 4 Adjust the screw to achieve above standard ...

Page 49: ... In case bobbin thread is wound unbalanced loosen the screw for bobbin winder thread guide slightly 2 Move bobbin winder thread guide vertically so that the bobbin thread is balanced when it is wound 3 Tighten the screw 4 Loosen the screw for bobbin presser slightly 5 Move the bobbin presser to adjust the amount of thread wound on it 6 Tighten the screw ...

Page 50: ...the position of 0 4 mm lower than its highest position ADJUSTMENT 1 Turn the pulley counterclockwise and set the needle at the position of 0 4 mm lower than its highest position 2 Loosen the screw of the rotary shutter 3 Turn the rotary shutter slowly and adjust N P shutter to be at the center of photo interrupter 4 Tighten the screw ...

Page 51: ...st position it should have enough distance from BH lever switch When BH lever is raised BH lever switch should be clearly ON ADJUSTMENT 1 Loosen the screw 2 Move the BH lever switch holder to adjust its position 3 Tighten the screw NOTE Make sure on the LCD if BH lever switch position is correct ...

Page 52: ...1 0 1 5 mm ADJUSTMENT 1 Loosen the screw for BT switch holder slightly 2 Use a standard screwdriver to move the top of the BT switch and adjust the clearance between the BT switch and the reverse sewing lever B 3 Tighten the screw Note Check that the BT switch turns on when the reverse sewing button is pressed and the stitch length dial is set to 0 ...

Page 53: ... 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 Move bobbin winder to the left 2 Loosen the screw 3 Adjust the switch by moving it left to right 4 Tighten the screw ...

Page 54: ...8 B349 B351 B352 STANDARD When pulling polyester thread 60 through slowly inner rotary hook tension should be 10 12g ADJUSTMENT 1 Thread polyester thread to inner rotary hook correctly and pull it slowly by using tension gauge 2 Adjust thread tension by using screwdriver ...

Page 55: ...imperfect performance 3 Lower the presser foot when you use needle threader 4 Nylon transparent thread is applicable in needle 14 16 5 Do not turn the balance wheel when you use needle threader 6 Do not touch needle threader when machine is running 7 Needle 9 might be hard to thread 8 Needle should be located above needle plate more than 8 0 mm for threading Thread Needle 30 50 60 80 100 120 9 11 ...

Page 56: ...ll 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 In case that hook does not get through eyelet of some needles Needles through which the hook does not get are bad ADJUSTMENT In case the hook is bad after above checking adjust the hook by forming with pliers...

Page 57: ...EDLE THREADER 1 Remove needle and lower the presser foot 2 Push down needle threader to take out 3 Place new one so that guide is immediately under the guide pin as shown Figure A 4 Push needle threader all the way up so that guide is placed in the pin ...

Page 58: ... the top of needle eye is zero 2 Threading is capable when needle is located higher than 8 0 mm from the needle plate CHECK Refer to illustration Case A Hook position is too high Hook hits needle and can t get through needle eye Case B Hook position is too low Hook gets through needle eye but it catches bottom part of needle ...

Page 59: ... the clearance between the top of hook and top of needle eye is zero 3 Check if part a and part b is parallel CASE B Hook point is too low 1 Set the needle position at right and loosen the screw 2 Adjust needle threader slightly up and check the clearance between the top of hook and top of needle eye is zero 3 Check if part a and part b is parallel NOTE Unless part a and part b is parallel hook wi...

Page 60: ... 58 IV 1 REMOVING THE COVERS 59 2 LAMP REPLACEMENT 60 3 LEAD WIRES ARRANGEMENT 61 LCD UNIT 62 DISPLAY SYSTEM 63 MOTOR CONTROL UNIT 64 TEST MODE Language Machine Specifications Settings 65 ...

Page 61: ...e rear cover by loosening six screws 4 Remove the front cover by loosening the screw NOTE INSTALLING THE FRONT COVER B338 B346 B347 B348 B349 A Set the pattern dial to the zigzag stitch and check that the line on the selecting cam aligns with the upper end of the release lever B Set the pattern on the front cover to the zigzag stitch ...

Page 62: ... 60 2 LAMP REPLACEMENT 1 Loosen the screw of face plate 2 Remove face plate 3 Attach new sew light bulb to lamp socket B338 B346 B347 B348 B341 B349 B351 B352 ...

Page 63: ... 61 3 LEAD WIRES ARRANGEMENT B338 B346 B347 B348 B341 B349 B351 B352 ...

Page 64: ... 62 LCD UNIT 1 LINE LCD TYPE ...

Page 65: ... 63 DISPLAY SYSTEM LCD control PCB LCD module 4 LINE LCD TYPE ...

Page 66: ... 64 MOTOR CONTROL UNIT 230V 120V MODE SWITCH UNIT 1 LINE LCD TYPE 4 LINE LCD TYPE ...

Page 67: ...r not there is a Drop Feed function and 3 the construction and operation of the bobbin case CB hook or Top bobbin 1 Press the key forward sequence or the key reverse sequence to set the desired specifications When all of the settings have been completed turn off the power supply to cancel the Test Mode 1 ENGLISH 9 SUOMEKSI FINNISH 2 DEUTSCH GERMAN 10 SVENSK SWEDISH 3 FRANCAIS FRENCH 11 CESTINA CZE...

Page 68: ... 66 BL6200 B338 BL6700 B341 H7110109 ...

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