Janome JP720, Servicing Manual

Page 1: ...SERVICING MANUAL JP720 JP760...

Page 2: ...Clearance between Needle and Hook Point Backlash Lower Shaft Gear Feed Dog Height Needle Swing Timming Top Tension Stretch Stitch Feed Balance Thread Plate Replacing the Electronic Components Locatio...

Page 3: ...HA x 11 blue tip needle Adjust the presser bar level to make the pressure stronger See mechanical adjustment Needle bar height See mechanical adjustment Needle to hook timing See mechanical adjustment...

Page 4: ...ch thread is wound on the bobbin 3 Lint is stuck inside the bobbin holder 4 Thread quality is too low 5 Thread is jamming around the bobbin holder Set the bobbin thread correctly Adjust the position o...

Page 5: ...tment backlash lower shaft gear Eliminate the looseness See part removal and replacement driving motor dc motor Oil all moving parts P 14 P 26 P 34 7 Deformation pattern 1 Inappropriate feed balance 2...

Page 6: ...To remove 1 Loosen the screw and lift the face cover to disengage the rib on the inside Remove the face cover To attach 2 Attach the face cover engaging the hook and the rib with the rear cover and ti...

Page 7: ...5 Bed cover Changing External Parts To remove 1 Shift the drop lever to the left 2 Loosen 4 screws and remove the bed cover To attach Follow the above procedures in reverse q w e q w e w w...

Page 8: ...e set screw and then remove the set screw and 3 Remove the cap and loosen set screw 4 Disconnect all the connectors from the circuit board A NOTE Do not disconnect the connectors by pulling on cord To...

Page 9: ...7 Changing External Parts Front cover 4 Disengage the hooks and stitch balance adjustment knob 5 Remove the front cover q q w w To attach Follow the above procedures in reverse...

Page 10: ...emove the front cover See pages 6 7 2 Loosen set screws and then remove the rear cover NOTE Remove the presser lifter from the rear cover first while presser lifter lowered To attach Follow the above...

Page 11: ...he feed dog below the needle plate Place a block 6 mm thick under the presser foot and lower the presser foot lifter 3 Loosen the setscrew Raise the presser foot lifter and tighten the setscrew firmly...

Page 12: ...te should be at least 0 2 mm on either side If not adjust as follows 1 Remove the face cover See page 4 2 Turn the power switch on and check the needle drop position 3 If the needle drop is out of pos...

Page 13: ...n simple zigzag maximum zigzag width 4 Turn the handwheel toward you until the tip of hook meets the right side of the needle 5 Loosen the setscrew 6 Adjust the height of the needle bar by moving the...

Page 14: ...he pattern simple zigzag maximum zigzag width 3 Remove the bed cover 4 Turn the handwheel toward you and set the needle bar at the lowest position 5 Loosen the setscrews on the lower shaft timing gear...

Page 15: ...needle Adjust the clearance between the test pin and the point of the hook in the left and right needle position to 0 1 to 0 05 mm by moving the hook set plate up or down 3 Tighten the setscrews 4 Ch...

Page 16: ...than 0 8 mm play adjust as follows Adjustment procedure 1 Remove the bed cover and loosen the setscrew 2 Turn the lower shaft bushing eccentric in the direction E when the play at hook tip is too smal...

Page 17: ...raight stitch pattern with maximum length 4 Turn the handwheel toward you to set the feed dog at the highest position 5 Loosen the setscrew and nut 6 Adjust the feed dog height by turning the adjustin...

Page 18: ...han 7 5 mm B If the swing point is lower than 6 3 mm 4 Shift the upper shaft shield plate to the left as close to the upper shaft sensor as possible It should not touch the upper shaft sensor 5 Check...

Page 19: ...ite If it is not within the above limit adjust as follows 1 Set the tension dial at 4 2 Lower the presser foot 3 Remove the front cover unit See P 6 7 2 Pull the spring away from the lead screw 3 If t...

Page 20: ...ction of D 6 If the length is too long turn the adjusting screw in the direction of C 7 Attach the base cap When a stretch pattern is sewn with the feed balancing dial set at the standard setting mark...

Page 21: ...the threader plate slashes or hits against the left or right side of the needle eye loosen the screw and adjust the hook position Fig B 2 If th hook of the threader plate slashes or hits against the...

Page 22: ...by pulling on the cord To disconnect grasp the connector not the cord Connect the connector to the connector post of the same color on the circuit board Bobbin winder switch Upper shaft sensor Lamp B...

Page 23: ...Notes Be careful the sewing machine may start running in its own while in test mode Turn off the power switch before replacing any parts Repeat the diagnostic test until the problem has been resolved...

Page 24: ...e second If you do not press the needle up down button within 2 5 seconds the machine automatically revert to the nor mal sewing mode Press needle uo down button LED displays 02 for one second Press n...

Page 25: ...78 The maximum value should be 370 to 390 When the speed control lever is at the left LED displays 00 The indicated value hexadecimal increase as you move the speed control lever to the right and fina...

Page 26: ...lume Lever Circuit board A To remove 1 Remove the front cover See pages 6 7 2 Pull out connectors from the circuit board A 3 Loosen 7 screws and remove the circuit board A To attach 1 Follow the above...

Page 27: ...sen the set screw and remove the board F To attach 1 Follow the above procedures in reverse q w r e e w q r NOTE Insert the lower part of the board F into the hole of rear cover when attaching the boa...

Page 28: ...motor and the motor belt with 2 screws 2 Loosen the set screws slightly and move the motor up or down to adjust the motor belt tension The belt should deflect 7 9 mm when applying 300 grams of load t...

Page 29: ...nt cover and the rear cover 2 Loosen 2 screws and a screw then remove the switching regulator To attach 3 Follow the above procedures in reverse NOTE Cords should not contact the lower shaft motor bel...

Page 30: ...otor Zigzag To remove 1 Remove the front cover and the rear cover 2 Remove 2 screws 3 Remove E ring 4 Remove stepping motor Zigzag To attach 1 Follow the above procedures in reverse NOTE Check the nee...

Page 31: ...ents To remove 1 Remove the front cover and the rear cover 2 Remove 2 screws 3 Remove E ring 4 Remove stepping motor Feed To attach 1 Follow the above procedures in reverse NOTE Check the stretch stit...

Page 32: ...gap between the slider and the buttonhole foot 6 Turn the adjusting screw to the left until the LED display changes from L to H 7 Next turn the adjusting screw right until the LED display changes fro...

Page 33: ...if any parts need to be luburicated OIL Use good quality sewing machine oil at the points A B C D E F G H J K indicated by black arrows A B C D F E G H I J K L Grease White grease is recommended for...