Janome 8050 User manual

SERVICE MANUAL
PARTS LIST
8050

INDEX
What to do when................................................................................................................................ 1 - 3
Changing External Parts
Face Cover..............................................................................................................................................4
Free-arm Cover ......................................................................................................................................5
Front Cover........................................................................................................................................ 6 - 7
Rear Cover ..............................................................................................................................................8
Mechanical Adjustment
Presser Bar Height ..................................................................................................................................9
Needle Drop Position.............................................................................................................................10
Adjustment of Hook Timing....................................................................................................................11
Replacing Hook .....................................................................................................................................12
Adjustment of Needle Bar Height ..........................................................................................................13
Clearance between Needle and Tip of Hook Rotary .............................................................................14
Feed Dog Height ...................................................................................................................................15
Top Tension ...........................................................................................................................................16
Replacing the Electronic Components
Circuit Board-A Connection ...................................................................................................................17
Self-diagnostic Test ......................................................................................................................... 18-22
Circuit Board-A ................................................................................................................................ 23-24
Driving Motor .........................................................................................................................................25
Switching Regulator Unit .......................................................................................................................26
Adjusting Buttonhole Lever Position......................................................................................................27
Parts List ....................................................................................................................................... 28-41

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 THE
FABRIC BEING SEWN.
5. SEWING ON
STRETCH FABRIC.
6. INAPPROPRIATE NEEDLE
BAR HEIGHT.
7. INAPPROPRIATE NEEDLE TO
HOOK TIMING.
8. INAPPROPRIATE NEEDLE TO
HOOK CLEARANCE.
9. HOOK IS BROKEN OR TOO
WORN.
INSERT THE NEEDLE PROPERLY.
CHANGE THE NEEDLE.
RETHREAD.
USE THE RECOMMENDED SEWING
NEEDLE AND THREAD.
USE A HA X #11 BLUE TIP NEEDLE.
SEE MECHANICAL ADJUSTMENT
“NEEDLE BAR HEIGHT”.
SEE MECHANICAL ADJUSTMENT “AD-
JUSTMENT OF HOOK TIMING”.
SEE MECHANICAL ADJUSTMENT
“CLEARANCE BETWEEN NEEDLE
AND TIP OF THE ROTARY HOOK”.
SEE “REPLACING HOOK”
P. 13
P. 11
P. 14
P. 12
2. FABRIC NOT
MOVING
1. INCORRECT FEED DOG
HEIGHT.
2. FEED DOG IS IN DOWN
POSITION.
3. THREAD ON BOTTOM SIDE OF
FABRIC IS JAMMED UP.
4. FEED DOG TEETH ARE WORN.
ADJUST THE PRESSER BAR LEVEL
TO MAKE THE PRESSURE STRON-
GER. SEE MECHANICAL ADJUST-
MENT “FEED DOG HEIGHT”.
RAISE THE FEED DOG.
MAKE SURE TO BRING BOTH NEEDLE
AND BOBBIN THREADS UNDER THE
FOOT WHEN START 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.
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. FABRIC IS BEING PULLED TOO
STRONGLY WHILE SEWING.
SEE MECHANICAL ADJUSTMENT
“NEEDLE DROP POSITION”.
CHANGE THE NEEDLE.
SEE MECHANICAL ADJUSTMENT
“CLEARANCE BETWEEN NEEDLE AND
TIP OF THE ROTARY HOOK”.
GUIDE THE FABRIC GENTLY WHILE
SEWING.
P. 10
P. 14

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.
5. UPPER SHAFT GEAR IS
LOOSE.
6. HOOK IS BROKEN OR TOO
WORN.
ELIMINATE THE BACKLASH.
ELIMINATE THE LOOSENESS.
SEE PART REMOVAL AND
REPLACEMENT “DRIVING MOTOR
(DC MOTOR)”.
OIL ALL MOVING PARTS.
ELIMINATE THE LOOSENESS.
SEE “REPLACING HOOK POINT”.
P. 25
P.12
7. DEFORMATION
PATTERN
1. INAPPROPRIATE FEED
BALANCE.
2. TOP TENSION IS TOO
STRONG.
ADJUST THE FEED BALANCING
SCREW.
SEE MECHANICAL ADJUSTMENT
“TOP TENSION”.
P. 16

4
CHanging exteRnal PaRts
faCe CoveR
to Remove:
1. LOOSEN THE SETSCREW qAND LIFT THE FACE COVER TO DISENGAGE THE RIB ON THE INSIDE.
REMOVE THE FACE COVER w.
to attaCH:
2. FOLLOW THE ABOVE PROCEDURES IN REVERSE.
q
w

5
fRee-aRm CoveR
to Remove:
1. LOOSEN THE SETSCREW qAND w. MOVE THE FREE-ARM COVER eTO THE LEFT.
REMOVE THE FREE-ARM COVER.
to attaCH:
FOLLOW THE ABOVE PROCEDURES IN REVERSE.
CHanging exteRnal PaRts
q
w
e

6
CHanging exteRnal PaRts
fRont CoveR (1)
to Remove:
1. REMOVE THE FACE COVER AND FREE-ARM COVER (SEE PAGE 8 AND 9).
2. REMOVE THE SETSCREWS (A) q(2 PCS.).
3. REMOVE THE SETSCREWS (B) w(5 PCS.), BACK COVER e.
4. REMOVE THE SETSCREWS (C) r(2 PCS.).
5. LOOSEN THE SETSCREW t.
6. DISCONNECT ALL THE CONNECTORS FROM THE CIRCUIT BOARD A.
note:
DO NOT DISCONNECT THE CONNECTORS BY PULLING ON CORD.
TO DISCONNECT, GRASP THE CONNECTOR, NOT THE CORD.
to attaCH:
7. FOLLOW THE ABOVE PROCEDURES IN REVERSE.
qw
ww
rr
e
t
THREAD TENSION
UNIT

7
CHanging exteRnal PaRts
fRont CoveR (2)
1. DISENGAGE THE FRONT COVER AND REAR COVER HOOKS.
2. REMOVE THE FRONT COVER.
to attaCH:
FOLLOW THE ABOVE PROCEDURES IN REVERSE.

8
CHanging exteRnal PaRts
ReaR CoveR
to Remove:
1. REMOVE THE FACE COVER AND FREE-ARM COVER (SEE PAGE 4 AND 5).
2. REMOVE THE SETSCREWS (A) q(4 PCS.).
3. REMOVE THE SETSCREWS (B) w(5 PCS.) AND BACK COVER.
4. REMOVE THE SETSCREWS (C) e(2 PCS.). REMOVE THE REAR COVER.
to attaCH:
5. FOLLOW THE ABOVE PROCEDURES IN REVERSE.
q
q
w
w
e
BACK COVER
REAR COVER

9
6.0 mm
meCHaniCal adjustment
PResseR baR HeigHt
THE DISTANCE BETWEEN THE BOTTOM OF THE PRESSER FOOT IN UP POSITION AND THE NEEDLE
PLATE SHOULD BE 6.0 MM.
1. REMOVE THE FACE PLATE AND NEEDLE.
2. LOWER THE FEED DOG BELOW THE NEEDLE PLATE. PLACE A BLOCK 6 MM THICK UNDER THE
PRESSER FOOT AND LOWER THE PRESSER FOOT LIFTER w.
3. LOOSEN THE SETSCREW q. RAISE THE PRESSER FOOT LIFTER AND TIGHTEN THE SETSCREW q
FIRMLY.
ATTACH THE NEEDLE AND FACE PLATE.
note:
MAKE SURE THAT THE PRESSER FOOT SHOULD BE PARALLEL TO THE FEED DOG SLOTS eIN THE
NEEDLE PLATE.
q
e
PRESSER FOOT SHOULD
BE PARALLEL TO THE FEED
DOG SLOTS.
w

10
0.2 MM
OR
MORE
0.2 MM
OR
MORE
A = B
meCHaniCal adjustment
needle dRoP Position
SET THE STITCH PATTERN TO “ ”. THE STANDARD NEEDLE DROP POSITION SHOULD BE AT CEN-
TER OF THE NEEDLE PLATE HOLE q. SELECT ZIGZAG STITCH “ ”, AND SET THE STITCH WIDTH AT
“5.0”. THE CLEARANCE BETWEEN THE NEEDLE AND THE EDGE OF THE NEEDLE HOLE SHOULD BE AT
LEAST 0.2 MM ON EITHER SIDE. IF NOT, ADJUST AS FOLLOWS:
1. TURN THE POWER SWITCH OFF. REMOVE THE FACE COVER. (SEE PAGE 4.)
2. LOOSEN THE HEXAGONAL SOCKET SCREW 3 X 4 w. ADJUST THE NEEDLE DROP POSITION BY
TURNING THE ECCENTRIC PIN.
THE DIRECTION OF ECCENTRIC PIN SHOULD BE AS SHOWN IN FIG. 1.
3. ATTACH THE FACE COVER.
note:
CHECK THE HOOK TIMING AFTER THIS ADJUSTMENT.
q
Fig. 1
w

11
THE AMOUNT OF ASCENDING TRAVEL OF THE NEEDLE BAR FROM ITS LOWEST POSITION TO THE
POSITION ( ) WHERE THE TIP OF THE ROTARY HOOK EXACTLY MEETS THE RIGHT SIDE OF THE
NEEDLE SHOULD BE 3.25 TO 3.55 MM.
1. REMOVE THE NEEDLE PLATE AND BOBBIN HOLDER.
2. TURN THE POWER SWITCH ON.
3. SELECT THE PATTERN (LEFT POSITION). SET THE ZIGZAG WIDTH AT 0.
4. REMOVE THE FREE-ARM COVER.
TURN THE HANDWHEEL TOWARD YOU TO LOWER THE NEEDLE AT ITS LOWEST POSITION.
5. LOOSEN THE HEXAGONAL SOCKET SCREW w(2 PCS.).
6. MOVE THE NEEDLE BAR 3.4 MM FROM THE LOWEST POSITION.
7. TURN THE LOWER SHAFT GEAR UNTIL THE TIP OF HOOK MEETS THE RIGHT SIDE OF THE NEEDLE
WHILE HOLDING THE HANDWHEEL.
8. TIGHTEN THE HEXAGONAL SOCKET SCREW w(2 PCS.).
9. ATTACH THE FREE-ARM COVER, BOBBIN HOLDER AND NEEDLE PLATE.
meCHaniCal adjustment
adjustment of Hook timing
w
NEEDLE PLATE
BOBBIN HOLDER
w
LOWER SHAFT
GEAR
LEFT POSITION ( )
(#14)
TIP OF HOOK MEETS
THE RIGHT SIDE OF
THE NEEDLE
LOWEST NEEDLE POSITION
3.25 – 3.55MM

12
RePlaCing Hook
iF THE HOOK POINT IS DAMAGED OR TOO WORN, THE HOOK NEEDS TO BE REPLACED.
to Remove:
1. REMOVE THE NEEDLE PLATE AND BOBBIN HOLDER.
2. REMOVE THE FRONT COVER (SEE PAGE 6 AND 7).
3. TURN THE HANDWHEEL TOWARD YOU TO ALIGN THE HOOK POINT AND THE RIGHT EDGE OF FEED
DOG TEETH.
4. MARK BOTH THE HANDWHEEL AND THE REAR COVER TO INDICATE WHERE THE HOOK POINT AND
THE RIGHT EDGE OF FEED DOG TEETH MEETS.
5. LOOSEN THE SETSCREW (A).
6. PUSH THE HOOK SHAFT(B) FROM THE HOLE (C) WITH ALLEN SCREWDRIVER.
REMOVE THE SHAFT, WASHERS (D), (E) AND (F).
* WASHERS (D) ARE TRANSPARENT. WASHER (E) HAS A PROJECTION ON ITS EDGE.
INSERT THE PROJECTION IN THE GROOVE OF THE GEAR WHEN ATTACHING.
7. REMOVE THE HOOK FROM THE HOOK RACE. DO NOT REMOVE THE FEED DOG TEETH WHEN
REMOVING IT.
to attaCH:
8. REVERSE THE PROCEDURE ABOVE. ALIGN THE HOOK POINT AND THE RIGHT EDGE OF FEED DOG
TEETH WHEN ATTACHING THE HOOK TO THE HOOK RACE. (MATCH THE MARKS ON THE
HANDWHEEL AND REARCOVER. WIPE OUT THE MARKS AFTER THIS ATTACHMENT.)
9. CHECK THE HOOK TIMING (SEE PAGE 11) AFTER THE REPLACEMENT.
IF NECESSARY, ADJUST THE HOOK TIMING.
NEEDLE PLATE SETSCREW
BOBBIN HOLDER
MARKS
meCHaniCal adjustment
NEEDLE PLATE
(A)
HOOK
HOOK
(B)
(D)
(E)
(D)
(F)
RIGHT EDGE OF FEED DOG TEETH
HOOK POINT

13
BEFORE PROCEEDING WITH THIS ADJUSTMENT, CHECK THE HOOK TIMING (REFER TO PAGE 11). THE
DISTANCE BETWEEN THE UPPER EDGE OF THE NEEDLE EYE AND THE TIP OF THE HOOK SHOULD
BE IN THE RANGE OF 1.6 TO 2.0 MM WHEN THE TIP OF THE HOOK TIMING MEETS RIGHT SIDE OF THE
NEEDLE IN THE LEFT NEEDLE POSITION ( ) AS THE NEEDLE ASCENDS FROM ITS LOWEST POSITION.
1. REMOVE THE NEEDLE PLATE, BOBBIN HOLDER AND FACE PLATE.
2. TURN THE POWER SWITCH ON.
3. SELECT THE PATTERN (LEFT POSITION). SET THE ZIGZAG WIDTH AT 0.
4. TURN THE HANDWHEEL TOWARD YOU UNTIL THE TIP OF HOOK MEETS THE RIGHT SIDE OF THE
NEEDLE.
5. LOOSEN THE HEXAGONAL SOCKET SCREW q.
6. MOVE THE NEEDLE BAR TO ADJUST THE NEEDLE BAR HEIGHT, AND TIGHTEN THE HEXAGONAL
SOCKET SCREW q.
BE CAREFUL NOT TO TURN THE NEEDLE BAR.
7. ATTACH THE BOBBIN HOLDER, NEEDLE PLATE AND FACE COVER.
meCHaniCal adjustment
adjustment of needle baR HeigHt
1.6 – 2.0 MM
HEXAGONAL SOCKET SCREW
NEEDLE SETTING GROOVE
UPPER EDGE OF NEEDLE HOLE
HOOK RACE (UNIT)
HOOK RACE
TIP OF HOOK MEETS THE RIGHT SIDE OF THE NEEDLE
LEFT POSITION ( )
(#14)
NEEDLE PLATE
BOBBIN HOLDER

14
adjustment PRoCeduRe:
1. REMOVE THE NEEDLE PLATE AND BOBBIN HOLDER. ATTACH THE MASTER NEEDLE. TURN THE
POWER SWITCH ON AND SET THE ZIGZAG WIDTH AT MAXIMUM.
2. REMOVE THE FACE COVER.
3. LOOSEN THE SETSCREW A (2 PCS.).
4. TURN THE HANDWHEEL TOWARD YOU. ADJUST THE CLEARANCE BETWEEN THE NEEDLE AND THE
TIP OF THE ROTARY HOOK, BY MOVING THE HOOK BASE PLATE UP OR DOWN, TO WITHIN –0.1 TO
+0.05 MM AT THE LEFT AND RIGHT NEEDLE POSITION.
5. TIGHTEN THE SETSCREW A (2 PCS.).
6. ATTACH THE FACE COVER. REMOVE THE MASTER NEEDLE. ATTACH THE BOBBIN HOLDER AND
NEEDLE PATE.
7. CHECK THE CLEARANCE BETWEEN THE NEEDLE AND THE EDGE OF THE NEEDLE HOLE IN THE
NEEDLE PLATE (SEE PAGE 10).
* THE CLEARANCE BETWEEN THE NEEDLE AND THE POINT OF HOOK SHOULD BE –0.1 TO +0.05 MM.
CleaRanCe between needle and tiP of tHe RotaRy Hook
meCHaniCal adjustment
TIP OF HOOK
–0.1 TO +0.05 MM
NEEDLE BAR SUPPORTER
ADJUSTING PLATE
HEXAGONAL SOCKET
SCREW (A)
NEEDLE PLATE
BOBBIN HOLDER

15
THE HIGHEST POSITION OF THE FEED DOG SHOULD BE BETWEEN 0.80 AND 0.90 MM FROM THE
SURFACE OF THE NEEDLE PLATE.
1. LOWER THE PRESSER FOOT AND TURN THE POWER SWITCH ON.
2. TURN THE HANDWHEEL TOWARD YOU TO SET THE FEED DOG AT THE HIGHEST POSITION.
3. REMOVE THE FREE-ARM COVER.
4. LOOSEN THE SETSCREW qAND NUT w.
5. ADJUST THE FEED DOG HEIGHT BY TURNING THE ADJUSTING SCREW e. THE HIGHEST POSITION
OF THE FEED DOG SHOULD BE BETWEEN 0.80 AND 0.90 FROM THE SURFACE OF THE NEEDLE
PLATE.
6. TIGHTEN THE NUT wAND SETSCREW q.
7. ATTACH THE FREE-ARM COVER.
feed dog HeigHt
meCHaniCal adjustment
a b
e
w
q
q
PRESSER FOOT
FEED DOG
0.80 – 0.90mm
SURFACE OF THE
NEEDLE PLATE

16
meCHaniCal adjustment
toP tension
THE TOP TENSION SHOULD BE BETWEEN 65 AND 80G WHEN PULLING THE THREAD UP IN THE
DIRECTION OF ARROW.
* USE POLYESTER SEWING THREAD #50 (WHITE).
* IF IT IS NOT WITHIN THE ABOVE LIMIT, ADJUST AS FOLLOWS.
1. SET THE TENSION DIAL “4”.
2. REMOVE THE COVER.
3. LOWER THE PRESSER FOOT.
• If the top tensIon Is too loose, turn the lead screw In the dIrectIon (a).
• If the top tensIon Is too tIght, turn the lead screw In the dIrectIon (B).
4. CHECK THE TOP TENSION AND ATTACH THE COVER.
WHITE POLYESTER THREAD SIZE 50
PULL THE THREAD AT THE SPEED OF 110 MM/SEC
IN THE DIRECTION OF ARROW
COVER

17
CiRCuit boaRd-a ConneCtion
note:
DO NOT DISCONNECT THE CONNECTORS BY PULLING ON CORD.
TO DISCONNECT, GRASP THE CONNECTOR, NOT THE CORD.
RePlaCing tHe eleCtRoniC ComPonents
r
y
u
i
o
!0!1
!2 PRINTED CIRCUIT BOARD A
PRINTED CIRCUIT
BOARD F
PRINTED CIRCUIT
BOARD L
qPRINTED CIRCUIT BOARD P
(BLACK)
wFEED MOTOR (WHITE)
eBOBBIN WINDING SWITCH
(BLUE)
rPOWER SWITCH (WHITE)
tZIGZAG WIDTH MOTOR (GREEN)
yPRINTED CIRCUIT BOARD F (WHITE)
uPRINTED CIRCUIT BOARD L (WHITE)
i GROUND WIRE OR
PROGRAM (RED)
o BUTTONHOLE SENSOR PROGRAM
(RED)
!0 PRESSER FOOT
LIFTER SWITCH
(GREEN)
!1 DC MOTOR (WHITE)
!2 CONTROLLER (BLACK)
q
w
e
t

18
to enteR self-diagnostiC mode:
PRePaRation:
1. TURN THE POWER SWITCH OFF.
2. MOVE THE BOBBIN WINDER SPINDLE TO THE LEFT.
3. RAISE THE FEED DOG.
4. SET THE SPEED CONTROL LEVER TO THE LEFT.
5. REMOVE THE PRESSER FOOT AND RAISE THE PRESSER FOOT LIFTER.
6. TURN THE HAND WHEEL TOWARD YOU TO RAISE THE NEEDLE TO ITS HIGHEST POSITION.
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.
• you can skIp steps In the dIagnostIc procedure and go dIrectly to the test you
WANT TO PERFORM.
(ENTER SELF-DIAGNOSTIC MODE, THEN SELECT THE STEP NUMBER OF THE DIAGNOSTIC TEST
YOU REQUIRE BY PRESSING THE START/STOP BUTTON)
to begin:
TURN ON THE SWITCH. IF ANY OF THE FOLLOWING PROBLEMS OCCUR, TAKE THE
RECOMMENDED ACTIONS IN THE ORDER THEY ARE SHOWN.
1. THE MACHINE DOES NOT RESPOND WHEN THE POWER SWITCH IS TURNED ON:
• check each connector connectIon
• replace the machIne socket
• replace the swItchIng regulator
• replace the a-Board
2. THE SEWING MACHINE LAMP DOES NOT LIGHT UP:
• replace the lIght BulB
• replace the a-Board
self-diagnostiC test
TURN THE POWER SWITCH
ON WHILE SIMULTANEOUSLY
PRESSING NEEDLE UP/DOWN
BUTTON AND THE LOCKING
STITCH BUTTON.
THE LCD DISPLAY WILL
INDICATE “01”.
PRESS THE START/STOP
BUTTON TO ENTER THE SELF-
DIAGNOSTIC MODE.