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(26) Easy adjustment procedure of bobbin thread detection
(Caution) Be sure to turn OFF the power to the sewing machine up to steps 1 through 2.
1) Draw out the connectors of CN18 and CN32 mounted on the microcomputer circuit board.
2) Insert 5-pin connector of jig into CN18.
In addition, connect the connector drawn out from CN32 to 3-pin connector of jig.
3) Take out the bobbin.
(26) -1 Adjusting VR1 (variable resistor 1) (adjusting the bobbin thresad remaining amount detection sensor)
1) Turn the hand wheel and turn ON the power to the sewing machine at 170˚ to 190˚. Connect the "–" side of the tester to the setscrew (GND)
located at the bottom on the right side of the microcomputer circuit board and connect the "+" side to 3-pin of CN-31 mounted on the
microcomputer circuit board. Then search the angle at which the voltage becomes highest.
2) Fix the hand wheel at the angle which has been searched and adjust VR1 so that the scale of the tester is 3.8V to 4.2V.
3) Return the hand wheel to its home position to complete the procedure.
(26) -2 Adjusting VR2 (variable resistor 2) (adjusting the limit sensor)
1) Turn the hand wheel and turn ON the power to the sewing machine at 170˚ to 190˚. Connect the "–" side of the tester to the setscrew (GND)
located at the bottom on the right side of the microcomputer circuit board and connect the "+" side to 1-pin of CN31 mounted on the
microcomputer circuit board. Then search the angle at which the voltage becomes highest.
2) Fix the hand wheel at the angle which has been searched and adjust VR2 so that the scale of the tester is 3.8V to 4.2V.
3) Return the hand wheel to its home position to complete the procedure.
(Perform this adjustment when replacing the microcomputer circuit board.)
How to adjust
How to adjust
How to adjust
Adjustment drawing
Microcomputer
circuit board
5-pin side
CN18
Connector
of jig
CN32
3-pin side
Adjustment drawing
VR1
VR2
Setscrew
CN31
Tester
36
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