Brother LH4-B800E Service Manual download pdf (Page 119)

LH4-B800E

5 - 4

5. Troubleshooting guide

Cause Check Solution page

Upper thread

scissors

Installation height Install the upper thread

scissors at the correct

height.

4-16

Upper thread scissors

opening timing

Adjust to an

appropriate opening

timing.

4-17

4-18

Upper thread

feeding

Thread take-up Decrease thread take-

up

Loosen the screw to decrease

thread take-up so that upper thread

does not pull out of scissors

assembly at the sewing start.

4-26

Bobbin

thread

(bobbin slip)

Bobbin thread tension Increase bobbin thread

tension

Bobbin thread tension

Whip stitch 0.15 - 0.25N

Purl stitch 0.05 - 0.15N

(Holding the thread steady the

bobbin case should gently descend

under the force if its own weight)

-

(Instruction)

Spring Apply spring -

Lower thread retainer

position

Adjust lower thread

retainer position

Adjust lower thread retainer so that

a 35 - 40 mm thread leader is left

after trimming

4-19

Bobbin presser

position

Adjust the bobbin

presser.

4-23

Bobbin insertion Insert the bobbin

correctly.

-

(Instruction)

Presser foot lifting

speed

Reduce the setting for

memory switch No. 02.

-

(Instruction)

5-3. Uneven seams 1)......Beginning of sewing (1)

35 - 40 mm

1 mm

Make a gap

Apply spring so that the end of

the rotary hook is even with

the inside edge of the bobbin

case rim

Screw

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