Adjustments; Synchronizer Model Db2-B737, B748, B774, B791 - Brother MD-602 Service Manual

12. Adjustments

12.1 Synchronizer Model DB2-B737 ·B748 ·B774 ·B791
Higher
The synchronizer detects the needle position with two sensors.
The thread trimming signal is timed to the needle down position signal and the treadle reverse signal.
When the power is turned on and the needle stopped in the down position, the distance between needle plate top and
needle set screw bottom should be 18 to 22mm.
When the needle is stopped in the up position and the pulley reference line is within the belt cover reference lines, the
distance between needle plate top and needle tip should be 10 to 12mm with thin and regular materials, 10 to 14mm
with thick materials. (With Model B748 the needle up stop position is 10-14mm.)
Adjust as follows when necessary.
Turn the power off.
Needle up position
1. Slightly loosen the two screws q.
Move the set screws q in the direction of normal pulley movement to raise the needle bar w stop position. Turn the
other way to lower the needle bar.
Needle down position
1. Set the treadle to reverse and then release it to neutral. (This is the needle down stop position.)
2. The distance between the needle plate top and the needle screw bottom should be 18-22mm.
3. Loosen screw e and move the synchronizer r to adjust.
* Check the needle up stop position.
* When the machine pulley is removed once, provide 0.5mm clearance between the pulley bottom and the synchronizer
for installation.
(Improper clearance causes improper machine operation.)
When the synchronizer is out of order...
Turn off the power switch and disconnect the synchronizer cord.
Use the machine with standard function (without thread trimming) until the synchronizer is replaced.
q
Lower
q
MD-602, 612
w
Needle up stop
Thin, regular materials: 10-12mm
Thick materials: 10-14mm
Needle down stop
18-22mm
0.5mm
Reference
line
27