Janome MB-7e Troubleshooting guide

SERVICE MANUAL
&
PARTS LIST
MODEL: MB-7e (V2)
First Edition: 02 October 2020

1
CONTENTS
Replacing the Spool Stand...........................................................................................4
Replacing the Thread tension panel.............................................................................4
Replacing the Head set right cover (unit) .....................................................................5
To Replace Right Cover and Left Cover.......................................................................6
Replacing the Base Cover and Bed Cover...................................................................7
Replacing the Thread Tension Panel and Thread Catcher Panel ................................8
Checking the Thread Paths (1).....................................................................................9
Checking the Thread Paths (2)................................................................................... 10
Replacing the Needle / Needle and Thread Reference Table .................................... 11
Adjusting the Bobbin Thread Tension......................................................................... 12
Checking the Lowest Position of the Needle.............................................................. 13
Replacing the Needle Bar Rest .................................................................................. 14
Replacing the Take-up Lever Cam Roller................................................................... 15
Adjusting the Take up Lever Timing............................................................................ 16
Replacing the Presser Foot Cam ........................................................................17 to 19
Replacing and Adjusting the Presser Foot (1)............................................................ 20
Replacing and Adjusting the Presser Foot (2)............................................................ 21
Replacing the Presser Foot Return Spring and Washer .....................................22 to 24
Replacing the Thread Catcher.................................................................................... 25
Replacing the Thread Catcher Hook ......................................................................... 26

2
Replacing the Jump Solenoid..................................................................................... 27
Adjusting a Play in the Moving Head.......................................................................... 28
Replacing the Moving Head (1).................................................................................. 29
Replacing the Moving Head (2).................................................................................. 30
Adjusting the Needle Drop Position (Back or Forth) .................................................. 31
Adjusting the Needle Height....................................................................................... 32
Replacing the Needle Bar, Needle Spring and Cushion............................................. 33
Replacing the Rotation Stopper Plate ........................................................................ 34
Replacing the Thread Take-up Lever ......................................................................... 35
Adjusting the Check Spring Tension........................................................................... 36
Adjusting the Check Spring Stroke ............................................................................ 37
Adjusting the Thread Catcher Holder ......................................................................... 38
Replacing the Thread Catcher Loop Tape.................................................................. 39
Replacing the Lateral Moving Unit.............................................................................. 40
Adjust the Hook Timing............................................................................................... 41
Adjusting the Position of the Hook Stopper................................................................ 42
Replacing the Thread Cutter Driving Roller................................................................ 43
Replacing the Dynamic Cutter Blade.......................................................................... 44
Replacing the Static Cutter Blade............................................................................... 45
Adjusting the Static Cutter Blade................................................................................ 46
CONTENTS

3
Adjusting the Dynamic Cutter Blade........................................................................... 47
Adjusting the Bobbin Thread Holder........................................................................... 48
Adjusting the Thread Keeper...................................................................................... 49
Adjusting the X-carriage Belt Tension......................................................................... 50
Replacing the X-carriage Belt..................................................................................... 51
Adjusting the Y-carriage Belt Tension ......................................................................... 52
Replacing the Y-carriage Belt ..................................................................................... 53
Adjusting the Timing Belt Tension............................................................................... 54
Replacing the Timing Belt........................................................................................... 55
Adjusting the Motor Belt Tension................................................................................ 56
Replacing the Motor Belt ............................................................................................ 57
Replacing the DC Motor ............................................................................................. 58
To Reset Motor Drive Time ......................................................................................... 59
Adjusting the Needle Upper Shaft Timing................................................................... 60
Adjusting the Moving Head Stop Position .................................................................. 61
Adjusting the Needle Stop Position ............................................................................ 62
Adjusting the Carriage Home Position........................................................................ 63
Securing the Cables in the Moving Head (Upper Part) .............................................. 64
Instructions for Updating MB-7/eXpressive 970 ..................................................65 to 69
PARTS LIST ...................................................................................................... 70 to 113
CONTENTS

4
Replacing the Thread tension panel
Setscrew
Spool stand
Thread tension panel
To remove:
1. Remove the setscrews(3 pcs.) and spool stand.
To attach:
2. Attach the spool stand and tighten the setscrews
(3 pcs.).
Setscrew
Replacing the Spool Stand
To remove:
1. Remove the setscrews (2pcs.) and thread tension
panel.
To attach:
2. Attach the thread tension panel and tighten the set-
screws(2 pcs.).
Setscrew

5
To remove:
1. Turn the RCS knob counterclockwise to remove it.
2. Remove caps, and setscrews A (2 pcs.).
Remove the head set right cover (unit).
3. Disconnect the Printed circuit board L2 connector and
printed circuit board K connector.
To attach:
4. Connect the Printed circuit board L2 connector and
Printed circuit board K connector.
5. Attach the head set right cover (unit) with the
setscrews A (2pcs.). Attach the caps (2pcs.).
6. Turn the RCS knob clockwise to attach the RCS knob.
Replacing the Head set right cover (unit)
RCS knob
Cap, Setscrew A
Hook
Printed circuit board L2 connector
Printed circuit board K connector
Head set right cover (unit)

6
Hook
Upper hook 1 Upper hook 2
Head set right cover (unit)
Right Cover
To remove:
1. Remove the LED lamp connector (see page 5).
Unhook the right cover from the hook.
• To remove the right cover, Unhook the cover
from upper hook 1, upper hook 2 and the
hook on handwheel side.
2. Remove caps (3 pcs.) and setscrews A (3 pcs.).
Remove the right cover.
To attach:
3. Attach the right cover with setscrews A and caps.
4. Attach the head set right cover (unit).
• Do not bind cords when attaching the right cover.
Left Cover
To remove:
1. Remove the caps (4 pcs.) and setscrews B(4 pcs.).
Remove the left cover.
To attach:
2. Attach the left cover with setscrews B (4 pcs.) and caps
(4 pcs.).
Cap, Setscrew A
Cap, Setscrew B
To Replace Right Cover and Left Cover
Right cover
Left cover

7
Base Cover
To remove:
1. Remove the setscrews A (6 pcs.).
2. Lift the back of the machine and remove the base cover
from the base cover.
To attach:
3. Attach the machine into the base cover.
4. Tighten the setscrews A (6 pcs.) securely.
Replacing the Base Cover and Bed Cover
Bed Cover
To remove:
1. Remove the setscrew B and setscrew C. Remove the
bed cover.
To attach:
2. Attach the bed cover with the setscrew B and setscrew
C.
Setscrew A
Setscrew B Setscrew C

8
Replacing the Thread Tension Panel and Thread Catcher Panel
To remove:
1. Remove the setscrews A (2 pcs.) and thread tension
panel.
2. Loosen the setscrews B (3 pcs.)
3. Remove the setscrews C, thread catcher panel and
lower thread guide plate.
Setscrew A
Setscrew A
Thread tension panel
Thread tension panel
Setscrew B
Setscrew B
Setscrew C
Thread catcher panel
Lower thread guide plate

9
A
Detecting roller
To avoid seam puckering, skipped stitches or thread
breaking, keep the thread paths in the best condition.
1. Tension control, detecting roller
a) Detecting rollers should spin smoothly.
b) Tension controls and detecting rollers
should be free from lint or dust.
2. Thread guide hole
a) There should be no burrs or scratches.
3. Thread take-up lever
a) There should be no burrs or scratches.
4. Lower guide plate
a) There should be no burrs or scratches.
5. Needle
a) Needles should not be bent or blunt.
To check the needle:
Touch the tip of the needle and slide it over on your nail
and slid it lightly.
The needle must be blunt if there is any scratch on your
nail after sliding the needle on your nail.
In that case, replace the needle.
 Placetheatsideoftheneedleontosomethingat
(needle plate, glass, etc.). The gap (A) between the
needleandtheatsurfaceshouldbeconsistent.
Replace the needle if the gap is not consistent.
Checking the Thread Paths (1)

10
6. Needle plate
a) There should be no burrs or scratches.
7. Presser foot
a) There should be no burrs or scratches,
especially inside of the presser foot hole.
b) There should be no warp in the presser
foot.
8. Hook race
a) There should be no burrs or scratches.
b) The tip of hook race should not be blunt.
c) There should be no detectable play in the hook
and hook race.
9. Thread keeper
a) There should be no burrs or scratches,
especially on the tip of the thread keeper.
10. Check spring
a) The check spring should not be worn.
Checking the Thread Paths (2)
Hook
Thread keeper
Upper side
Lower side

11
Replacing the Needle
To remove:
1. Loosen the needle clamp screw.
2. Remove the needle.
To attach:
3. Insert the needle into the needle clamp with the long
groove facing you. Push the needle up as far as it will
go.
4. Tighten the needle clamp screw.
Needle clamp screw
Needle
Long groove
Needle and Thread Reference Table
Use DBxK5Q1NY needles and select an appropriate size of
needle for threads and fabrics to be sewn.
An inappropriate size of needle may cause skip stitches,
thread breakage or loose seam.
Please refer to the table below and select the
suitable needle size.
75 8 to10
120 9 to 11
200 11 to 14
Thread Size (Denier)
Polyester
Needle Size

12
* Use cotton thread size 120.
1. Guide the thread to the left to pass it into the guide
path as shown.
2. Pulling the thread from the front hole in the direction
of arrow, measure the thread tension with a tension
meter.
The thread tension should be in the range of 20 to
30 grams-force.
If not, adjust the thread tension by turning the
adjusting screw.
1
2
Adjusting the Bobbin Thread Tension
Thread
Front hole
Tension meter
Front hole
Adjusting screw
Rear view
Guide path
Side view

13
Checking the Lowest Position of the Needle
1. Remove the spool stand, head set right cover (unit)
right cover and left cover (see pages 5 to 6).
2. Turn the handwheel to set the index disk at 270°.
3. Push the needle bar down to engage the needle bar
clutch.
4. Turn the handwheel to set the needle bar at its lowest
position.
Use a lever type dial indicator to measure the needle
bar height.
5. Turn the handwheel clockwise until the indicator reads
0.2 mm and read the angle (Aº) of the index disk.
Turn the handwheel counterclockwise until the indicator
reads 0.2 mm and read the angle (Bº) of the index disk.
Calculate the mean angle (Cº): C=(A+B–360)÷2
Turn the handwheel clockwise to set the index disk at
Cº.
Loosen the setscrews (2 pcs.) and set the pointer at 0º
(L). Tighten the setscrews (2 pcs.) securely.
Check the following items if you have adjusted the
lowest position of the needle.
• Upper shaft timing
• Take-up lever timing
• Hook timing
• Thread cutter timing
Lever type dial indicator
Setscrew Pointer

14
Replacing the Needle Bar Rest
To remove:
1. Remove spool stand, head set right cover (unit), lateral
moving unit, right cover and left cover.
2. Disconnect the thread catcher unit connector.
Remove the setscrews A (2 pcs.) and setscrew B.
Remove the thread catcher unit.
3. Loosen the setscrew C. Pull the main shaft up and
remove it from the machine.
4. Loosen the setscrew D and remove the needle bar rest
from the main shaft.
To attach:
5. Reverse the procedure above. Attach the needle bar
main shaft so its bottom end is level with the bottom
surface of the head frame.
6. Adjust the needle height after the replacement.
Setscrew A
Thread
catcher unit
connecter
Setscrew B
Main shaft
Setscrew C
Needle bar rest Setscrew D
Bottom of the head frame

15
To remove:
1. Remove spool stand, head set right cover (unit), right
cover, left cover and thread tension panel. (see pages 4
to 6 and 8).
2. Remove the setscrews (3 pcs.) and drive cover.
3. Remove the thread take-up lever spring with pliers.
4. Loosen the setscrew. Remove the thread take-up lever
shaft, thread take-up lever unit and washer.
5. Loosen the setscrew. Remove the cam roller shaft and
cam roller.
To attach:
6. Reverse the procedure above.
When attaching the thread take-up lever shaft, tighten
the screw while pressing the thread take-up lever shaft
lightly.
Drive cover Setscrew
Thread take-up lever spring
Setscrew
Thread take-up lever shaft Thread take-up
lever unit
Cam roller
Cam roller
shaft
Setscrew
Washer
Thread take-up
lever shaft
Replacing the Take-up Lever Cam Roller

16
Adjusting the Take-up Lever Timing
To remove:
1. Remove spool stand, head set right cover (unit), right
cover and left cover.
2. Turn the handwheel to set the index disk at 6º.
3. Insert the positioning pin from the left side of the arm.
The positioning pin goes into the pin groove of take-up
lever cam if the timing is correctly adjusted.
4. If the timing is incorrect, loosen the setscrew on the cam
clamp and turn the take-up lever cam so the positioning
pin can go into the pin groove on the cam.
Turn the handwheel to set the index disk at 6º. Tighten
the setscrew on the cam clump while pressing the
take-up lever cam to the side of the dynamic head.
There should be no gap between the take-up lever cam
and cam clamp.
5. Pull the positioning pin out from the arm.
Turn the handwheel to set the index disk at 270º.
Attach the removed parts.
Positioning pin
Pin groove
Take-up lever cam
Setscrew
Cam clamp
Take-up lever cam
Cam clamp

17
Replacing the Presser Foot Cam (1)
1Remove the spool stand, head set right cover, right cover,
left cover, moving head, thread catcher (unit)
and needle bar rest.
* The lateral moving unit is not needed to remove.
2 Remove the setscrews A (2 pcs.) and the left face plate.
3 Loosen the setscrew A. Pull the main shaft up.
Remove the presser foot block (unit).
4 Remove the snap ring E.
Loosen the setscrews B (2 pcs.).
Push the supporting shaft from the backside and pull the
supporting shaft out to the front.
Remove the presser foot lever (unit), poly slider and rulon
washer.
Setscrew A
Left face plate
Setscrew A Main shaft
Supporting shaft
Presser foot block
Presser foot lever (unit)
Setscrew B Snap ring-E
Poly slider
Rulon washer
Setscrew B
*The presser foot cam shall be replaced as the crank unit.
Rulon washer
1. Remove the spool stand, head set right cover, right
cover, left cover, moving head, thread catcher (unit)
and needle bar rest.
* The lateral moving unit is not needed to remove.
2. Remove the setscrews A (2 pcs.) and the left face plate.
3. Loosen the setscrew A. Pull the main shaft up.
Remove the presser foot block (unit).
4. Remove the snap ring-E.
Loosen the setscrews B (2 pcs.).
Push the supporting shaft from the backside and pull
the supporting shaft out to the front.
Remove the presser foot lever (unit), poly slider and
rulon washer.
Replacing the Presser Foot Cam (1)
*You need to remove the crank when replacing the presser foot cam.

18
Replacing the Presser Foot Cam (2)
5 Loosen the setscrews C (2 pcs.).
6 Remove the setscrew B.
Pull the crank out to the front to remove it.
Setscrew C
Crank (unit)
Setscrew B
5. Loosen the setscrews C (2pcs.).
6. Remove the setscrew B.
Pull the crank out to the front to remove it.
Replacing the Presser Foot Cam (2)