Adjusting The Upper Thread Feeding Amount; Adjusting The Feed Timing Belt - Brother LH4-B800E Service Manual

4. Adjustment

4-19. Adjusting the upper thread feeding amount

1. Loosen the screw q, and then turn the tension take-up lever w to adjust the upper thread feeding amount.
* Move the trimmer driving arm by hand and check that upper thread feeding is completed before the upper thread
is cut. If the above adjustment is not made, it may result in the upper thread pulling out or in upper thread clamping
errors.

4-20. Adjusting the feed timing belt

q
w
1. Remove the adjustment bolt q.
2. Loosen the three screws w so that the feed pulse motor e moves easily.
3. While using a spring gauge to push the notch in the motor mounting bracket r with a force of 98 N, tighten the
screws w.
4. Check that the timing belt t moves smoothly.
5. Gently tighten the adjustment bolt q.
If you do not have a spring gauge, loosen the three screws w and adjust using the adjustment bolt q. Adjust the
tension so that the amount of belt deflection is approximately 3.5 mm when a force of 5 N is applied in the middle of the
belt span.
4 - 26
w
w
q
t
w
e
r
F = 98 N (10 kgf)
w
LH4-B800E