Brother S-7200B Service Manual
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Brother S-7200B Service Manual

Single needle direct drive straight lock stitcher with thread trimmer
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S-7200B
SERVICE MANUAL
(MD-741B, 751B, 741C, 751C)
Please read this manual before making any adjustments.
SINGLE NEEDLE DIRECT DRIVE STRAIGHT LOCK STITCHER
WITH THREAD TRIMMER

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  • Page 1 S-7200B SERVICE MANUAL (MD-741B, 751B, 741C, 751C) Please read this manual before making any adjustments. SINGLE NEEDLE DIRECT DRIVE STRAIGHT LOCK STITCHER WITH THREAD TRIMMER...
  • Page 2 This service manual is intended for S-7200B; be sure to read the S-7200B instruction manual before this manual. Carefully read the “SAFETY INSTRUCTIONS” and the whole of this manual to understand this product before you start maintenance. As a result of research and improvements regarding this product, some details of this manual may not be the same as those for the product you purchased.

  • Page 3: Safety Instructions

    ) indicates something that you must do. The picture inside the circle indicates the · · · · · nature of the thing that must be done. (For example, the symbol at left means “you must make the ground connection”.) S-7200B...
  • Page 4 Keep the oil out of the reach of children. with correct operation may also occur. S-7200B...

  • Page 5: Maintenance And Inspection

    Turn off the power switch before inserting or Any problems in machine operation which result removing the plug, otherwise damage to the control from unauthorized modifications to the machine will box could result. not be covered by the warranty. S-7200B...
  • Page 6 Be sure to connect the ground. If the ground connection is not secure, you run a high risk of receiving a serious electric shock, Safety devices: and problems with correct operation may also occur. (A) Finger guard (B) Thread take-up cover Direction of operation Oil pan Control box 3629M S-7200B...

  • Page 7: Table Of Contents

    (When using the operation panel)......34 6-14. Setting the needle up stop position and needle down stop position (If using the control box panel) ..... 35 6-15. Adjusting the treadle ..........37 6-16. Adjusting the presser foot floating amount (minute lifting amount) ............37 S-7200B...

  • Page 8: Machine Specifications

    Lubricated / Lubricated / Rotary hook RP for light materials for medium materials for heavy materials (lubrication-free rotary hook) Lubricating oil -30[], -40[] -33[], -43[] -45[] Rotary hook High-speed spindle High-speed spindle Needle bar Special Brother grease Special Brother grease S-7200B...

  • Page 9: Notes On Handling

    Returning the machine head to the upright position 1. Clear away any tools, etc. which may be near the table holes. 2. While holding the face plate with your left hand, gently return the machine head to the upright position with your right hand. 2089M S-7200B...

  • Page 10: Function Settings (Operation Panel)

    When the main display is green, normal key operations such as the start backtack key and the fixed stitch key cannot be used. Press the MAX key once more to clear the sewing speed display and return to the orange display. Normal key operations can then be carried out. S-7200B...

  • Page 11: Using The Lock Key

    (NOTE 2) The treadle unit should also be adjusted when using this function. (Refer to page 56.) (NOTE 3) When set to ON, treadle operation is disabled, so it should always be left at OFF. If set to ON, the messages “ 「 ” (green) and “ ” (orange) will flash alternately in the display. S-7200B...

  • Page 12: Setting Functions

    ・ If you change the function number after changing the setting value but before pressing the ENTER key, the setting value will not be changed. You need to press the ENTER key for each function number for the setting to be accepted. S-7200B...

  • Page 13: Function List

    (NOTE 2) Presser foot will not drop if DIP switch 1 is set to OFF. *… Enabled if the control box model is MD-741A/751A. (Alternating): The presser foot is raised or lowered each time the optional actuator is pressed. (Momentary): The presser foot is raised only while the optional actuator is being pressed. S-7200B...
  • Page 14 (NOTE 5) Stitch number setting is enabled when Function No. 118 is set to “2” or “3”. (NOTE 6) Stitch number setting is enabled when Function No. 118 is set to “3”. (NOTE 7) Operates when treadle is lightly pressed when Function No. 31 is set to “0”. S-7200B...
  • Page 15 Enabled if the control box model is MD-741A/ 751A. **… (Alternating): The presser foot is raised or lowered each time the optional actuator is pressed. (Momentary): The presser foot is raised only while the optional actuator is being pressed. S-7200B...
  • Page 16 (NOTE 15) Presser foot lifter pedal operation is not included. In the case of simultaneous operation, the standing operation pedal takes priority. (NOTE 16) Setting is only enabled when DIP switch 1 is set to ON. *… Settings indicated with " * " are enabled when the power is turned off and then back on. S-7200B...
  • Page 17 (Example) Default settings: At low speed: 0°; At high speed: 150° Needle up stop point is home point Operating angle range Direction of main shaft rotation Operating angle (At low speed: No. 59) 0654B (At high speed: No. 60) S-7200B...
  • Page 18 (NOTE 19) Operation is disabled when Function No. 62 is set to “1”. Presser foot is raised after needle bar is raised. (NOTE 20) Used when you would like to match the seam accurately during automatic backtacking. Use Function No. 78 to set the stop position and Function No. 79 to change the time before restarting. S-7200B...
  • Page 19 ・ When the high speed switch is pressed, the sewing speed returns to the maximum sewing speed that has been set using the MAX key. <When set as an option actuator> Connect to connector CN9 on the control circuit board. Option Actuator 2251M ・ Set the operation using Function No. 11. S-7200B...
  • Page 20 ・ The delay time after thread trimming until output turns off is set using Function No. 112. If the needle stops in the down position after the edge of the material is detected, output turns off when the needle stops. Motor Option Needle up signal Fixed stitch number E Material edge sensor signal 2253M S-7200B...
  • Page 21 ・ After thread trimming, output is synchronized with the automatic presser foot lifter. ・ Use Function No. 111 and No. 112 to set the timer operation. ・ When the presser foot is lowered, option output turns off. Needle up stop Motor Presser foot lifting Option 2256M S-7200B...
  • Page 22 ・ If the values are set to values that are greater than the initial value (+ direction), the quick reverse solenoid on/off timing becomes slower. If the seam length immediately after switching occurs is short, change the setting to a value in the + direction. S-7200B...
  • Page 23 (ex. 1) Setting for Function No. 80 Speed Neutral Treadle backward stroke Depression stroke 2258M (ex. 2) Setting for Function No. 83 Speed Neutral Treadle backward stroke Depression stroke 2259M (ex. 3) Setting for Function No. 85 Speed Neutral Treadle backward stroke Depression stroke 2260M S-7200B...
  • Page 24 (NOTE 27) This is the upper limit for the start backtacking speed setting. Refer to page 3 for details on start backtacking speed settings. (NOTE 28) This setting is read from the head detector unit. (NOTE 29) This is the upper limit for the maximum sewing speed setting. Refer to page 3 for details on maximum sewing speed settings. S-7200B...
  • Page 25 External output; signal is open collector output within maximum 10 mA 2262M Motor Needle up signal Variable input signal Output signal 2263M NOTE: If Function No. 112 and No. 113 are set to “0”, output is synchronized with the variable input signal. S-7200B...
  • Page 26 When set to “3”, stitch number G is set for function No. 23, stitch number H is set for Function No. 24 and stitch number I is set for Function No. 25. This step is skipped if the number of stitches is zero. S-7200B...
  • Page 27 Cumulative power on time (Actual time = Displayed time x 10) Cumulative operating time (Actual time = Displayed time xxxx x 10) Cumulative grease-up running time (Time = Display xxxx x 1 hour) / Grease life estimate (%) ROM version (x.xxx) Set maximum speed history (rpm) S-7200B...

  • Page 28: Clearing Saved Data (Initialization)

    When initialization is complete, the main display will change to green and “init rPM” will be displayed. After this, the operation panel and the treadle can be operated. When an operation is carried out, the display will return to the normal display. S-7200B...

  • Page 29: Initializing The Control Box Panel

    (The display will turn off.) (Display turns off) 2. After this, “Ar” will flash and the initialization will be complete. (5 seconds or more) 3150M Set DIP switch -3 to ON. (The settings will be locked.) S-7200B...

  • Page 30: Adjusting The Rotary Hook Lubrication Amount (-[]0[], []3[] Specifications)

    “Checking the lubrication amount” above. * Turn the adjusting screw (3) and check the lubrication 3686M amount repeatedly until the lubrication amount is correct. 4. Check the lubrication amount again after the sewing machine has been used for approximately two hours. S-7200B...

  • Page 31: Adjustments

    Adjust so that it is in a position where it is easy to operate. 1. Remove the two screws (2). Back 2. Move the switch setting base (3) to move the actuator (1) to the preferred position <A> or <B>. 3. Tighten the two screws (2). 3687M 3688M S-7200B...

  • Page 32: Adjusting The Safety Switch Position

    If the spring stroke is too small, the safety switch will not operate. 3.5 mm or more Sewing machine Table Clearance is too large. By changing the position of the safety switch, the required spring stroke can be maintained. Reduce the clearance. 3690M 3692M S-7200B...

  • Page 33: Adjusting The Thread Take-Up Spring

    NOTE: If using the tension gauge (7) (sold separately) to measure the tension, take the reading from the scale on the side of the red line. <-[][]S> <-[][]3> <-[][]5> 0.1 - 0.24N 0.25 - 0.35N 0.3 - 0.5N 3694M S-7200B...

  • Page 34: Adjusting Arm Thread Guide R

    (1) is at the standard height of 6 mm. 5. Tighten the bolt (6). 6. Replace the oil cap (5). 7. Adjust the presser foot pressure using the adjustment screw (4), and then tighten the nut (3). 2278M S-7200B...

  • Page 35: Adjusting Of The Feed Dog Height

    [B]) lower (Refer to “6-7. Adjusting the feed dog angle” on the next page for details of this operation.) 3696M Becomes higher Needle plate Standard Becomes lower 2281M Becomes higher Becomes higher Standard Standard Becomes lower Becomes lower 2282M S-7200B...

  • Page 36: Adjusting The Feed Dog Angle

    Needle has been adjusted, so it will be necessary to re-adjust the plate height of the feed dog (1). Standard Lower the front 2284M Back is lowered Raise the front Standard Standard Back is raised Lower the front 2285M S-7200B...

  • Page 37: Adjusting The Needle Bar Height

    NOTE: Do not turn the vertical cam (3) too far in the Needle timing is Needle timing (Standard) direction of (C), otherwise it could cause the advanced is retarded needle to break. 3. After adjustment is completed, securely tighten the two 3699M screws (5). S-7200B...

  • Page 38: Adjusting The Needle And Rotary Hook Timing

    The clearance should be 0.4 - 0.7 mm for -[][]S / [][]3 models, and 0.6 - 1.1 mm for -[][]5 models. <-[][]S / [][]3> 0.4 - 0.7mm <-[][]5> 0.6 - 1.1mm 2293M 3700M S-7200B...

  • Page 39: Adjusting The Thread Trimming Timing

    * Tighten the screw (8) so that there is no play in the forked shaft (9). * The lower thread finger (10) must be underneath the movable knife (6). 3. Install the feed dog, needle plate and presser foot. Mating mark 1208B S-7200B...

  • Page 40: Adjusting The Thread Take-Up Amount (-[][]3 Specifications)

    (2) until it touches the screw stop on the thread take-up support shaft (4). 6. After this, tighten the set screw (3). 7. Install the two rubber caps (1). 8. Install the face plate. Screw stop 3677M S-7200B...

  • Page 41: Adjusting The Needle Up Stop Position (When Using The Operation Panel)

    * A setting value of “10” corresponds to an angle of rotation of approximately 10° for the upper shaft. * If DIP switch 3 is not set to OFF, this adjustment cannot be Becomes higher carried out. Becomes lower 3657M 2138M 2139M S-7200B...

  • Page 42: Setting The Needle Up Stop Position And Needle Down Stop Position (If Using The Control Box Panel)

    Set DIP switch -3 to OFF. (This will cancel the lock so that the functions can be set.) Control box 3143M While pressing the end backtack key (1), press the power switch (2) to turn on the power. 0706B S-7200B...
  • Page 43 1. Press the start backtack key (3) so that “ - ” is displayed in the top row of the stitch number display. 2. Press the end backtack key (1) to set the value. (Example: 3) Becomes lower Becomes higher 0705B Set DIP switch -3 to ON. (The settings will be locked.) S-7200B...

  • Page 44: Adjusting The Treadle

    Turn the adjusting screw (5) clockwise. ・ To lower the presser foot (1) ... Turn the adjusting screw (5) counterclockwise. 5. Tighten the nut (4). * After making the adjustment, sew a piece of material to check the floating amount. Raise Lower 3701M S-7200B...

  • Page 45: Replacing Parts

    (4) can be seen. 7. Remove the two screws (4), and then remove the movable knife (5). * Carry out the above steps in reverse to install the movable knife (5). 0739B S-7200B...

  • Page 46: Motor And Timing Belt

    9. Pull out the timing belt (4) by hand while being careful not to get it caught on the fan (12). < Motor removal > Carry out steps 1 and 2 and steps 6 to 8 of <Timing belt removal>. 1211B S-7200B...
  • Page 47 After the timing belt has been installed, be sure to then carry out the steps in <Timing belt installation check> (refer to the next page). < Motor installation > 1213B Carry out steps 2 to 5 and step 10 of <Timing belt 1214B installation>. S-7200B...
  • Page 48 5. Set the sewing machine to needle up stopping, and then operate the sewing machine and let it stop. Check that the reference line (d) on the machine pulley (5) is within the range of the mark (e) on the motor cover (3) at this time. S-7200B...

  • Page 49: Rotary Hook Rp

    (B) of the bed.) NOTE: If the sewing machine is used while the adjusting screw (5) is in the fully-tightened position, it will cause oil to leak out through the gap between the rotary hook shaft (6)and the bracket (7). 0741B S-7200B...

  • Page 50: Feed Bar Shaft, Lifting Feed Shaft

    4. Apply grease to the meshing areas ( areas) of each part. Grease 5. Install each part to the sewing machine. 2319M Grease Lifting feed shaft unit Grease Grease 2317M Grease Grease Be particularly sure to apply grease to the groove 0742B S-7200B...

  • Page 51: Applying Grease (-[]3[], []5[] Specifications)

    If this happens, apply grease and carry out the reset procedure. * If you continue to use the sewing machine after carrying out the reset procedure but without applying grease, problems with the sewing machine may result. <Applying grease> Use Brother-specified <GREASE (SA7300-001)>. Using the tube 3682M S-7200B...
  • Page 52 The buzzer will make a long beep, and then the main display (1) will change to stitch number display mode. 7. Depress the treadle to run the sewing machine for 1 second or more. 8. Turn the power switch to “OFF”. (This completes the reset procedure.) 2139M S-7200B...

  • Page 53: When Using The Control Box Panel

    If this happens, apply grease and carry out the reset procedure. * If you continue to use the sewing machine after carrying out the reset procedure but without applying grease, problems with the sewing machine may result. <Applying grease> Use Brother-specified <GREASE (SA7300-001)>. Using the tube 3682M S-7200B...
  • Page 54 5. Then, press and hold the end backtack key (4) for 5 seconds or more. (The display will turn off.) 6. After this, “Gr” will flash and the reset operation will be complete. 7. After the reset operation is complete, set DIP switch -3 to ON. (The settings will be locked.) 2139M S-7200B...

  • Page 55: Control System

    (6) that is attached to the DD motor (5). The thread trimming operation is carried out immediately before the sewing machine stops at the needle up stop position. S-7200B...

  • Page 56: Control Box And Motor

    4. Loosen the nuts (11) and (12) (without removing them). 5. Remove the bolt (13) and nut (14). 2323M 6. Pivot the control box around the bolt (15) and pull it out to remove it from the table. <Installation> Install by following the removal procedure in reverse. 2324M S-7200B...

  • Page 57: Control Box And Motor Rating Plate

    USA/Mexico Canada Destination Oceania (C-TICK) Turkey/ North Africa China Europe/Greece (CE) 100V 110V 200V Power supply voltage 220–240V 380–415V 1 forward 1 backward step type Treadle unit 2 forward 2 backward step type Operation panel External Sewing machine S-7200A S-7200B...
  • Page 58 10. CONTROL BOX AND MOTOR <Motor> Serial No. 2326M 2327M S-7200B...

  • Page 59: Control Circuit Board

    For input/output signals used by external devices Option connector 3 Connect to stitch counter actuator. CN10 Cooling fan power supply connector Only used for three-phase high-voltage specifications. CN16 Thermistor connector Connect to shorted connector when not using three-phase high-voltage specifications. S-7200B...
  • Page 60 Option signal output 1 LED2 Option signal output 2 LEFT_UP_SW Option signal input 1 Sewing speed actuator (high speed) RIGHT_UP_SW Option signal input 2 Sewing speed actuator (medium speed) RESET_SW Option signal input 3 Sewing speed actuator (low speed) 0V (GND) S-7200B...

  • Page 61: Checking The Motor And Power Supply

    Measure the AC voltage between terminals 2–3. 200 V type (200–240 V) [A] For three-phase <200 V type> Measure the AC voltage between terminals 4–5, 5–6 and 6–4. [B] For single-phase Measure the AC voltage between terminals 4–6. 1884M S-7200B...

  • Page 62: Checking The Solenoids

    If the values are as shown in the table below, the Knee switch connector is normal. Between 3–6 Presser lifter solenoid: Approx. 9.6 Ω Between 4–5 When knee switch is pressed: 0 Ω Presser lifter solenoid When knee switch is released: ∞ Ω 2331M S-7200B...

  • Page 63: Treadle Unit Assembly

    OFF, the presser foot lifter control signal is not output when the treadle is depressed backward after the knee switch has been used to raise the presser foot. Furthermore, if Function No. 41 is set to “1”, the presser foot lifter control signal is not output when the treadle is depressed backward. S-7200B...

  • Page 64: Standard Setting Values

    ・ For treadle unit -H, the point of change (F) in the forward depression force is between S1 and S2, and the point of change (R) in the backward depression force is between S6 and S7. Speed Backward depression Neutral Forward depression 1841M S-7200B...

  • Page 65: Setting Method For Standard Depression Strokes

    “PdFF x.xxx” will appear in the main display (3). (x.xxx indicates the depression voltage.) 2333M 2) Memorizing the maximum forward position With the treadle depressed forward to the maximum forward position, press the thread trimming key (2). “Pdnn x.xxx” will appear in the main display (3). 2334M S-7200B...
  • Page 66 The buzzer will sound and the main display (3) will switch off. NOTE: If you do not press the ENTER key (4), the settings will not be memorized. 2337M 2. Turn off the power switch (1). 3. Set DIP switch No.4 to OFF. 0653B S-7200B...
  • Page 67 “PF” will appear in the stitch number display (3). 3195M 2) Memorizing the maximum forward position With the treadle depressed forward to the maximum forward position, press the start backtack key (4). “Pn” will appear in the stitch number display (3). 3196M S-7200B...
  • Page 68 With the treadle depressed backward to the maximum backward position, press the start backtack key (4). The stitch number display (3) will switch off. 3198M 5) Completion of setting 1. Turn off the power switch (1). 2. Set DIP switch No.4 to OFF. 0653B S-7200B...

  • Page 69: Standing Operation Pedal

    Connect the foot plug (1) to connector CN3 on the control circuit board. Connect the standing pedal connector (2) to the foot plug (1). Secure the cord (3) of the standing pedal with the shielded wire clip (5) and the cable tie (4). S-7200B...

  • Page 70: Connectors

    High-speed switch Thread trimmer switch Spare Low-speed switch Presser foot switch Variable speed input Ground 0702B <At pedal> NOTE: Connector types Manufacturer Connector No. Connector terminal MOLEX 1292 P 1380 TL 1867M <A> Two-step pedal <B> Variable speed pedal 1868M S-7200B...

  • Page 71: Troubleshooting

    Is the thread take-up spring too weak? Adjust the tension of the thread take-up spring. Is the needle and rotary hook timing correct? Adjust the height of the needle bar. Adjust the clearance between the needle and the tip of the rotary hook. 0470M S-7200B...
  • Page 72 Use the sewing speed control keys to gradually reduce the manual sewing speed. Is the angle of the feed dog correct? Tilt the front of the feed dog down slightly. 0978M Material slippage Is the presser foot pressure too strong? Adjust the presser foot pressure. Instruction manual 0750M S-7200B...
  • Page 73 Incorrect thread trimming Is the needle properly installed? If it is incorrect, install the needle correctly. Instruction (Upper thread or lower manual thread being Is the fixed knife or movable knife blunt? trimmed) Replace the fixed knife or the movable knife. S-7200B...
  • Page 74 (If the power cord is too long or too many appliances are being run from a single outlet, this may cause voltage drops which will in turn cause the reset function to activate and stop the machine, even if the power supply itself is normal.) S-7200B...
  • Page 75 Insert connector Instruction securely. manual 3154M “GrEASEUP” “GU” This display is to notify you that it is time to apply grease. flashes panel Apply grease. 44, 46 display when the power switch is turned on. S-7200B...

  • Page 76: Error Code Displays

    Is the motor connector disconnected from the control box? (Motor lock) Insert the connector securely. Has the machine locked up? Turn off the power and then turn the machine pulley by hand and check that it turns easily. 2202M S-7200B...
  • Page 77 (Solenoid Check the resistances of the solenoids. overcurrent) Problem with control P.C. board. Replace the control box. Is connector CN5 inside the motor disconnected? Insert the connector securely. (Problem with motor over- heating sensor) 3116M S-7200B...
  • Page 78 If there is a problem, replace the cooling fan. The settings in “Setting method for standard depression stroke” may be incorrect. Redo the settings in “Setting method for standard depression stroke”. 58, 60 (Treadle pedal Problem with treadle unit. position error) Replace the treadle unit. S-7200B...
  • Page 79 Is DIP switch No.4 inside the control box set to ON? (diP SW4) Set DIP switch No.4 to OFF. 3160M If an error code that is not listed above appears or if carrying out the specified remedy does not solve the problem, contact the place of purchase. S-7200B...
  • Page 80 Thread trimming solenoid timeout EEROM error Control box overheating Treadle pedal position error Thermistor error If an error code that is not listed above appears or if carrying out the specified remedy does not solve the problem, contact the place of purchase. S-7200B...

  • Page 81: Segment Display Definition Table

    14. SEGMENT DISPLAY DEFINITION TABLE 14. SEGMENT DISPLAY DEFINITION TABLE LCD display character list 1203B S-7200B...
  • Page 82 MEMO S-7200B...
  • Page 83 MEMO S-7200B...
  • Page 84 SERVICE MANUAL S-7200B Printed in Japan I6100914B 2007. 03. B (1)

This manual is also suitable for:

Md-741bMd-751bMd-741cMd-751c

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