Janome NH40 User manual

SERVICE MANUAL
MODEL: NH40

CONTENTS
What to do when................................................................................................................................ 1 - 3
SERVICE ACCESS
Face Cover ............................................................................................................................................. 4
Bed Cover .............................................................................................................................................. 5
Free-arm Cover ...................................................................................................................................... 6
Front Cover............................................................................................................................................. 7
Rear Cover ............................................................................................................................................. 8
MECHANICAL ADJUSTMENT
Presser Bar Height ................................................................................................................................. 9
Needle Drop Position............................................................................................................................ 10
Needle to Hook Timing ......................................................................................................................... 11
Needle Bar Height ................................................................................................................................ 12
Clearance between Needle and Hook Point......................................................................................... 13
Backlash ( Lower Shaft Gear ).............................................................................................................. 14
Feed Dog Height .................................................................................................................................. 15
Needle Swing Timing............................................................................................................................ 16
Needle Thread Tension......................................................................................................................... 17
Stretch Stitch Feed Balance ................................................................................................................. 18
Adjust the Buttonhole Lever Position.................................................................................................... 19
REPLACING THE ELECTRONIC COMPONENTS
Location of the Connectors .................................................................................................................. 20
Self Diagnostic Tests ..................................................................................................................... 21 - 25
Circuit Board-A ..................................................................................................................................... 26
Driving Motor ........................................................................................................................................ 27
Switching regulator ............................................................................................................................... 28
Stepping motor ( Zigzag )..................................................................................................................... 29
Stepping motor ( Feed )........................................................................................................................ 30
Oiling .................................................................................................................................................... 31

1
Condition Cause How to fix Reference
1. Skipping
Stitches
1. Needle is not inserted properly.
2. Needle is bent or worn.
3. Incorrectly threaded.
4. Needle or thread are
inappropriate for fabric being
sewn.
5. Sewing on stretch fabric.
6. Presser foot pressure is too
weak.
7. In appropriate needle bar height.
8. Inappropriate needle to hook
timing.
9. Inappropriate needle to hook
clearance.
Insert the needle properly.
Change the needle.
Rethread.
Use the recommended sewing needle
and thread.
Use a 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 " Clearance
between needle and hook ".
P. 12
P. 11
P. 13
2. Fabric not
moving
1. Foot pressure foot is too weak.
2. Incorrect feed dog height.
3. Feed dog is in down position.
4. Thread on bottom side of fabric
is jammed up.
5. Feed dog teeth are worn.
Adjust the presser bar level to make the
pressure stronger.
See mechanical adjustment " Feed dog
height ".
Raise the feed dog.
Make sure to bring both needle and bob-
bin threads under the foot when starting
sewing.
Change the feed dog.
P. 15
WHAT TO DO WHEN

2
Condition Cause How to Fix Reference
3. Breaking
upper thread.
1. Initial sewing speed is too fast.
2. Thread path is incorrect.
3. Needle is bent or dull.
4. Top tension is too strong.
5. Needle size is inappropriate for
fabric.
6. Needle eye is worn.
7. Needle hole in needle plate is
worn or burred.
Start with medium speed.
Use the proper thread path.
Replace with a new needle.
Adjust top tension correctly.
Use appropriate needle for fabric and
thread in use.
Change the needle.
Repair the hole or replace the needle
plate.
P. 17
4. Breaking
bobbin thread.
1. Bobbin holder is incorrectly
threaded.
2. Too much 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 of bobbin winder
stopper.
Clean the bobbin holder.
Change to a high quality sewing thread.
Clear out the jamming thread.
5. Needle
breakes
1. Needle is hitting the needle plate.
2. Needle is bent or worn.
3. Needle is hitting the hook.
4. The fabric moves while the needle
is piercing it, or the needle zigzags
while in fabric.
5. Fabric is being pulled too strongly
while sewing.
See mechanical adjustment " Needle
drop position ".
Change the needle.
See mechanical adjustment " Clearance
between needle and hook ".
See mechanical adjustment " Needle
swing timing ".
Guide the fabric gently while sewing.
P. 10
P. 13
P. 16

3
Condition Cause How to fix Reference
6. Noisy
operation
1. Backlash between hook gear and
lower shaft gear is too great.
2. Lower shaft gear is loose.
3. Inappropriate belt tension.
4. Not enough oil
See mechanical adjustment
“backlash (lower shaft gear)”.
Eliminate the looseness.
See part removal and replacement
“driving motor (DC motor)”.
Oil all moving parts.
P. 14
P. 27
P. 31
7. Deformation
pattern
1. Inappropriate feed balance.
2. Inappropriate needle swing
timing.
3. Top tension is too strong.
See mechanical adjustment
“stretch stitch feed balance”.
See mechanical adjustment
“Needle swing timing”.
See mechanical adjustment
“Needle thread tension”.
P. 18
P. 16
P. 17

4
SERVICE ACCESS (1)
FACE COVER
TO REMOVE:
1. Remove the cap and setscrew (A) and remove the face cover while pushing the rib (B) up.
TO INSTALL:
2. Attach the face cover, engaging the hook (C) and the rib (B) with the rear cover and tighten screw (A)
3. Attach the cap.
Face cover
Setscrew (A)
Cap Rib (B)
Hook (C) Hook (C)

5
BED COVER
TO REMOVE:
1. Remove the 4 setscrews (A), remove the bed cover.
TO INSTALL:
2. Follow the above procedures in reverse.
SERVICE ACCESS (2)
Setscrew (A)
Setscrew (A)
Setscrew (A)
Bed cover
Setscrew (A)

6
FREE-ARM COVER
TO REMOVE:
1. Remove the needle plate.
2. Remove the bed cover (see page 5).
3. Loosen the setscrew (A) and (B).
TO INSTALL:
4. Follow the above procedures in reverse.
SERVICE ACCESS (3)
Setscrew (A) Setscrew (B)
Free-arm cover
Needle plate

7
FRONT COVER
TO REMOVE:
1. Remove the face cover, bed cove and free-arm cover (see page 4–6).
2. Loosen the setscrew (A) and (B) then remove the setscrew (D) and (E).
3. Remove the cap and loosen setscrew (C).
4. Disconnect all the connectors from the circuit board-A (see page 20).
NOTE:
Do not disconnect the connectors by pulling on cord.
To disconnect, grasp the connector, not the cord.
Remove the presser lifter from the front cover first while presser lifter lowered.
(To be continued)
SERVICE ACCESS (4)
Setscrew (B)
Setscrew (A)
Setscrew (C)
Setscrew (D)
Setscrew (E)
Cap
Cap

8
SERVICE ACCESS (5)
REAR COVER
TO REMOVE:
1. Remove the front cover (see pages 7).
2. Loosen setscrews (A).
3. Remove the setscrews (B), (C), (D) and (E), then remove the rear cover.
TO INSTALL:
4. Follow the above procedure in reverse.
Setscrew (B)
Setscrew (A)
Setscrew (C)
Setscrew (E)
Rear cover
Setscrew (D)

9
MECHANICAL ADJUSTMENT
PRESSER BAR HEIGHT AND ALIGNMENT
When the presser foot is raised, the clearance between the presser foot and the needle plate should be 5.7-6.3 mm.
When the presser foot is lowered, the edge of the foot and the feed dog window on the needle plate should be
parallel.
1. Remove the face cover (see page 4) and raise the presser foot.
Loosen the setscrew to adjust the presser foot height (6.0 mm) and the presser foot alignment.
2. Tighten the setscrew firmly.
3. Install the face cover.
Presser bar lifter
Setscrew
Presser foot
6.0 mm
Needle plate
[Height of presser foot]
[Presser foot alignment]
Should be parallel
Feed dog

10
NEEDLE DROP POSITION
Set the stitch pattern to " ". The standard needle drop position should be at center of the needle plate hole.
Select zigzag stitch " ", and set the stitch width at " 5.0 ". The clearance between the needle and the edge of the
needle hole in the needle plate 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 position, adjust it to proper position by turning the adjusting screw so that the needle is
in the center of the needle hole when the straight stitch " " is selected.
4. Check the needle drop position of the zigzag stitch " " with the maximum width.
5. Attach the face cover.
NOTE:
Check the hook timing after this adjustment.
MECHANICAL ADJUSTMENT
Needle plate hole
0.2 mm or more0.2 mm or more
A=B
Adjusting screw

11
MECHANICAL ADJUSTMENT
NEEDLE TO HOOK TIMING
When the machine is set for zigzag stitch (maximum zigzag width) at the right needle position, the amount of
ascending travel of the needle bar from its lowest position at the right needle drop to the position where the tip of the
hook meets the right side of the needle should be 1.4 to 2.0mm.
1. Remove the needle plate and bobbin holder.
2. Turn on the power switch, select the pattern " " (simple zigzag). (maximum zigzag width)
3. Remove the bed cover (see page 5).
4. Turn the handwheel toward you, and set the needle bar at the lowest position.
5. Loosen the 2 setscrews on the lower shaft gear.
6. Raise the needle bar 1.6 mm from the lowest position of the needle bar.
7. Turn the lower shaft gear until the tip of hook meets with the right side of needle.
8. Tighten the setscrews on lower shaft gear.
9. Attach the bed cover, bobbin holder and needle plate.
Lower shaft gear
Match the tip of hook at
the right side of needle
Needle #14
1.4-2.0 mm
Setscrews (2)
Bobbin holder
Needle plate
Lower needle position

12
MECHANICAL ADJUSTMENT
NEEDLE BAR HEIGHT
When the tip of the hook meets the right side of the needle in ascending travel of the needle from its right and lowest
position, the distance between the top of the needle eye and the tip of the hook should be in the range of 3.0 to 3.6 mm.
1. Remove the face cover (see page 4), needle plate and bobbin holder.
2. Turn on the power switch.
3. Select the pattern (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 needle bar upward or downward without turning it.
(Make sure that the needle setting groove of the needle bar is in the front).
7. Tighten the setscrew.
8. Insert the bobbin holder, then attach the needle plate and face cover.
Needle #14 Hook race
3.0-3.6 mm
Upper edge of needle eye
Hook race unit
Setscrew
Bobbin holder
Needle plate
Tip of hook meets right side of needle
Needle setting groove

13
MECHANICAL ADJUSTMENT
CLEARANCE BETWEEN NEEDLE AND HOOK POINT
* The clearance between the needle and the point of hook should be –0.1 to +0.05 mm.
PREPARATION:
1. Remove the needle plate, bobbin holder, and bed cover, and replace the needle with the test pin.
2. Turn the power switch on, and select pattern (simple zigzag). (maximum zigzag width)
ADJUSTMENT PROCEDURE:
1. Loosen the setscrews (A), (B), (C), then slightly tighten the hinge screw (C).
2. Turn the handwheel toward you to bring the hook point behind the 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 (A), (B), (C).
4. Check the backlash of the hook, gear and lower shaft gear (see page 14).
5. Attach the bed cover, needle plate and bobbin holder, and remove the test pin.
Hinge screw (C)
Setscrew (B)
Setscrew (A)
Bobbin holder
Needle plate
–0.1 to +0.05 mm
Test pin
Point of hook
Hook set plate

14
MECHANICAL ADJUSTMENT
BACKLASH (LOWER SHAFT GEAR)
TO CHECK:
1. Turn the power switch off.
2. Remove the needle plate and bobbin holder.
3. Turn the handwheel slowly toward you until the tip of the hook is between both ends of feed dog.
4. Rock the hook race with fingers to check the rotary play. It should be within 0.8 mm.
*If there is more than 0.8 mm play, adjust as follows.
ADJUSTMENT PROCEDURE:
1. Remove the bed cover (see page 5) and loosen the setscrew.
2. Turn the lower shaft bushing (eccentric), in the direction " A " when the play at hook tip is too small.
3. Turn the lower shaft bushing (eccentric), in the direction " B " when the play at hook tip is too large.
4. Tighten setscrew securely after adjustment.
Backlash allowance
Point of hook
Check the backlash
Groove of the lower shaft bushing
Lower shaft gear
A
B
Groove
Setscrew
A
B

15
MECHANICAL ADJUSTMENT
FEED DOG HEIGHT
The highest position of the feed dog should be between 0.80 and 0.90 mm from the surface of the needle plate.
1. Remove the bed cover (see page 5).
2. Turn the power switch on.
3. Select the straight 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 adjusting screw.
7. Tighten the nut and setscrew.
Presser foot
Feed dog
0.80-0.90 mm
Surface of the needle plate
To raise
To lower
Adjusting screw
Nut
Setscrew

16
MECHANICAL ADJUSTMENT
NEEDLE SWING TIMING
The needle should start to swing between 7.7 and 8.7 mm above the surface of the needle plate when the machine
is set for zigzag stitching.
1. Remove the front cover (see pages 7).
2. Turn on the power switch, select the pattern " ", and set the machine at the maximum zigzag width.
3. Turn the handwheel toward you slowly with your hand until the needle start to swing.
Loosen the setscrew and turn the upper shaft shield plate in the direction of:
A: If the swing point is higher than 8.7 mm.
B: If the swing point is lower than 7.7 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 the swing point by turning the handwheel, then tighten the setscrew.
6. Attach the front cover.
Needle #14
7.7–8.7 mm
Surface of needle plate
Upper shaft shield plate
Setscrew
Upper shaft sensor
B
A

17
MECHANICAL ADJUSTMENT
NEEDLE THREAD TENSION
The top tension should be between 75 and 90g when pulling the thread up in the direction of "C".
* Use polyester sewing thread #50 (White).
* 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 (see page 7).
4. Pull the spring (D) away from the lead screw.
If the top tension is too loose, turn the lead screw (E) in the direction "A".
If the top tension is too tight, turn the lead screw (E) in the direction "B".
Thread (polyester sewing
thread (#50 white))
Pull this way
C
(D)
(E)
A
B

18
MECHANICAL ADJUSTMENT
STRETCH STITCH FEED BALANCE
When a stretch pattern is sewn with the feed balancing dial set at the standard setting mark '' '', the pattern should
be as indicated with the '' '' mark in the figure below. (If the stitch feed is not balanced, adjust it as follows:
1. Set the machine to the adjustment mode (See illustration below).
2. Set the slit of the feed balancing dial at the standard setting mark '' '' on the front cover.
3. Enter the adjusting mode. Sew the stitch pattern "8" until the machine stop automatically, and check the stitch
length.
* Standard length of five "8" characters: 32 mm to 40 mm
4. Remove the base cap.
5. If the length is too short, turn the adjusting screw in the direction of "D".
6. If the length is too long, turn the adjusting screw in the direction of "C".
7. Attach the base cap.
(Enter the adjustment mode)
Turn the power switch on while
pressing the reverse button.
Press the ring button (left) mark.
The LCD display indicates "01".
Press the ring button (up) mark
indicate "08".
32-40mm
C D
Adjusting screw
Feed balancing dial
Standard setting mark
Base cap
Press the ring button (right) mark
indicate "88".