promelectroavtomat MC4900QC User manual
SERVICE MANUAL
MODEL MC4900QC
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TABLE OF CONTENTS
WHAT TO DO WHEN .............................................................................................................................. 1-3
SERVICE ACCESS (1) FACE COVER....................................................................................................... 4
SERVICE ACCESS (2) TOP COVER......................................................................................................... 5
SERVICE ACCESS (3) REPLACING THE BELT COVER ......................................................................... 6
SERVICE ACCESS (4) REPLACING THE BED COVER........................................................................... 7
SERVICE ACCESS (4) REPLACING THE BASE ...................................................................................... 7
SERVICE ACCESS (5) REPLACING THE FRONT COVER...................................................................... 8
SERVICE ACCESS (6) REPLACING THE REAR COVER ........................................................................ 9
ADJUSTING PRESSER FOOT HEIGHT AND ALIGNMENT .................................................................. 10
NEEDLE DROP POSITION ALIGNMENT ............................................................................................... 11
ADJUSTING HOOK TIMING.................................................................................................................... 12
ADJUSTING NEEDLE BAR HEIGHT ...................................................................................................... 13
ADJUSTING CLEARANCE BETWEEN NEEDLE AND HOOK ............................................................... 14
ADJUSTING BACKLASH BETWEEN HOOK DRIVE GEAR AND LOWER SHAFT GEAR .................... 15
FEED DOG HEIGHT ADJUSTMENT....................................................................................................... 16
ZIGZAG SYNCHRONIZATION................................................................................................................. 17
NEEDLE THREAD TENSION .................................................................................................................. 18
STRETCH STITCH FEED BALANCE...................................................................................................... 19
REPLACEMENT AND ADJUSTMENT OF THE NEEDLE THREADER PLATE ...................................... 20
CONNECTOR DIAGRAM ........................................................................................................................ 21
SELF DIAGNOSTIC TESTS ............................................................................................................... 22-25
REPLACING PRINTED CIRCUIT BOARD “A”......................................................................................... 26
REPLACING PRINTED CIRCUIT BOARD “K” AND “F”........................................................................... 27
REPLACING DC MOTOR AND ADJUSTING MOTOR BELT TENSION.................................................. 28
REPLACING THE FUSES ....................................................................................................................... 29
REPLACING MACHINE SOCKET ........................................................................................................... 30
REPLACING THE TRANSFORMER........................................................................................................ 31
REPLACING THE ZIGZAG WIDTH MOTOR ........................................................................................... 32
REPLACING FEED STEPPING MOTOR................................................................................................. 33
ADJUSTING BUTTONHOLE LEVER POSITION .................................................................................... 34
ADJUSTING THE BOBBIN WINDING SWITCH ...................................................................................... 35
ADJUSTING KNEE LIFTER HEIGHT ...................................................................................................... 36
OILING ..................................................................................................................................................... 37
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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. INAPPROPRIATE NEEDLE
BAR HEIGHT.
8. INAPPPROPRIATE 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 #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. 1 3
P. 1 2
P. 1 4
2. FABRIC NOT
MOVING
1. PRESSER FOOT PRESSURE
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 BOBBIN.
THREAD UNDER THE FOOT WHEN
STARTING SEWING.
CHANGE THE FEED DOG.
P. 1 6
WHAT TO DO WHEN
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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. UPPER THREAD 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 NEEDLE THREAD TENSION
CORRECTLY.
USE APPROPRIATE NEEDLE FOR
FABRIC AND THREAD IN USE.
CHANGE THE NEEDLE.
REPAIR THE HOLE OR REPLACE
THE NEEDLE PLATE.
P. 1 8
4. BREAKING
BOBBIN
THREAD
1. INCORRECITLY THREADED
BOBBIN.
2. TOO MUCH THREAD IS
AROUND ON THE BOBBIN.
3. LINT IS STUCK INSIDE THE
BOBBIN HOLDER.
4. THREAD QUALITY IS
TOO LOW.
5. THREAD IS JAMMING
AROUND THE BOBBIN.
THREAD BOBBIN CORRECTLY.
ADJUST THE POSITION OF STOPPER.
CLEAN THE SHUTTLE.
CHANGE TO A HIGH QUALITY
SEWING THREAD.
CLEAR OUT THE JAMMING THREAD.
5. NEEDLE
BREAKS
1. NEEDLE IS HITTING THE
NEEDLE PLATE.
2. NEEDLE IS BENT OR WORN.
3. NEEDLE IS HITTING THE
SHUTTLE.
4. THE FABRIC MOVES WHILE
THE NEEDLE IS PIERCING
IT, OR THE NEEDLE ZIGZAGS
WHILE IN FABRIC.
5. FABIRIC IS BEING PULLED TOO
STRONGLY WHILE SEWING.
SEE MECHANICAL
ADJUSTMENT “NEEDLE POSITION”.
CHANGE THE NEEDLE.
SEE MECHANICAL ADJUSTMENT
“CLEARANCE BETWEEN NEEDLE
AND HOOK”.
SEE MECHANICAL ADJUSTMENT
“ZIGZAG SYNCHRONIZATION”.
GUIDE THE FABRIC GENTLY
WHILE SEWING.
P. 1 1
P. 1 4
P. 1 7
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3
CONDITION CAUSE HOW TO FIX REFERENCE
6. NOISY
OPERATION
1. BACKLASH BETWEEN SHTTLE
HOOK GEAR AND LOWER
SHAFT GEAR IS TOO GREAT.
2. LOWER SHAFT GEAR IS
LOOSE.
3. INAPPROPRIATTE 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. 1 5
P. 2 8
P. 3 7
7. DEFORMATION
PATTERN
1. INAPPROPRIATE FEED
BALANCE.
2. INAPPROPRIATE ZIGZAG
SYNCHRONIZATION.
3. UPPER THREAD TENSION
IS TOO STRONG.
SEE MECHANICAL ADJUSTMENT
“STRETCH STITCH FEED BALANCE”.
SEE MECHANICAL ADJUSTMENT
“ZIGZAG SYNCHRONIZATION”.
SEE MECHANICAL ADJUSTMENT
“NEEDLE THREAD TENSION”.
P. 1 9
P. 1 7
P. 1 8
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4
SERVICE ACCESS (1)
FACE COVER (UNIT)
TO REMOVE:
REMOVE THE CAP AND SETSCREW.
REMOVE THE FACE COVER
TO ATTACH:
FOLLOW THE PROCEDURE ABOVE IN REVERSE.
SETSCREW
CAP
FACE COVER
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5
SERVICE ACCESS (2)
SETSCREW (A)
CARRYING HANDLE
SETSCREW
FACE PLATE
TOP COVER (UNIT)
TO REMOVE:
RAISE THE CARRYING HANDLE AND THE SETSCREW (A).
OPEN THE TOP COVER AND REMOVE THE SETSCREW (B).
LIFT UP THE TOP COVER AND REMOVE IT FROM THE REAR SIDE.
TO ATTACH:
FOLLOW THE PROCEDURE ABOVE IN REVERSE.
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6
SETSCREW (A)
CARRYING
HANDLE
SETSCREW (B)
SERVICE ACCESS (3)
REPLACING THE BELT COVER
TO REMOVE:
1. RAISE THE CARRYING HANDLE AND LOOSEN THE SCREW (A).
2. LOOSEN THE SCREW (B) AND THE BELT COVER.
TO ATTACH:
FOLLOW THE PROCEDURE IN REVERSE.
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7
SETSCREW (B)
SETSCREWS (A)
DROP FEED DOG
LEVER
BED COVER (UNIT)
SETSCREW (C)
SETSCREW (A)
SETSCREW (D)
SETSCREW (E)
BASE
SERVICE ACCESS (4)
REPLACING THE BED COVER (UNIT)
TO REMOVE:
PUSH THE DROP FEED DOG LEVER TO THE LEFT. REMOVE THE SETSCREWS (A), THEN REMOVE
THE BED COVER (UNIT).
TO ATTACH:
PUSH THE DROP FEED DOG LEVER TO THE LEFT. ATTACH THE BED COVER (UNIT) AND TIGHTEN
THE SETSCREWS (A).
REPLACING THE BASE
TO REMOVE:
REMOVE THE SETSCREWS (A), (B), (C), (D) AND (E).
REMOVE THE BASE.
TO ATTACH:
FOLLOW THE PROCEDURE IN REVERSE.
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8
SERVICE ACCESS (5)
REPLACING THE FRONT COVER (UNIT)
TO REMOVE:
REMOVE THE FACE COVER (UNIT), TOP COVER (UNIT) AND BELT COVER. (SEE PAGE 7, 8)
LOOSEN THE SETSCREWS (A), (B) AND (C). THEN REMOVE THE FRONT COVER (UNIT). DISCONNECT
THE CONNECTOR FOR PRINTED CIRCUIT BOARD-F AND FLEXIBLE FLAT CABLE FROM THE PRINTED
BOARD-A.
NOTE:
NEVER PULL ON CORD WHEN DISCONNECT THE CABLES FROM THE CIRCUIT BOARD.
TO ATTACH:
FOLLOW THE PROCEDURE IN REVERSE.
SETSCREW (C)
SETSCREW (B)
SETSCREW (A)
FRONT COVER
SETSCREW (A)
SETSCREW (B)
SETSCREW (C)
CONNECTOR FOR
PRINTED CIRCUIT
BOARD F
FLEXIBLE FLAT CABLE
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