typical GT1790A, Instruction Book

Page: 82 / 85

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IX. Trouble and Corrective Measures
Troubles Causes Corrective measures Page
1. Needle thread
breakage
1. Thread tension at parallel section is too
high.
 Decrease the thread tension at parallel
section.
25
2. Thread take-up spring tension is too strong
and stroke is too large.

Decrease the tension of the thread
take-up spring or decrease its stroke.
64
3. There is a burr or scratch on the blade
point of hook.
 Buff the blade point of hook, or
replace the hook.
—
4. Hook timing is not proper.
 Adjust the timing of hook by use of
synchronous ruler.
61
5. There is a scratch on the thread path.

Polish the thread path with sand paper
and buff it.
—
6. Attaching needle is wrong.
 Adjust again the direction, height, etc.
14
7. Needle is too thin. 
Replace the needle with a thicker one.
—
8. Needle tip is damaged.

Replace the needle.
—
9. Thread breaks when it is bent
 Do not pass the thread through the
thread guide pin.
12
2. Needle thread slips
off
1. Needle thread trimmer opens too early.
 Needle thread clamp opens too late
during needle thread cutting.
62
2. Whip stitching is not formed at the start of
sewing.

Decrease tension at the start of sewing.
36
(Tension at the start of sewing is too high.)
3. Threading needle thread is wrong.
 Thread properly again.
15
4. Speed at the start of sewing is too fast.
 Set the soft-start function.
52
3. Wobbling at
parallel section
1. Decrease the thread tension at parallel
section.

Increase the thread tension at parallel
section.
25
2. Bobbin thread tension is too high.
 Decrease tension of the bobbin thread.
16
(Purl stitch: 0.05 to 0.1N)
3. Tension is too low.

Increase the tension.
—
4. Wobbling at the
start of sewing
1. Decrease the thread tension at parallel
section.
 Increase the thread tension at parallel
section.
25
2. Position of needle thread trimmer is too
high.

Lower the needle thread trimmer to
such an extent that it does not come in
contact with the presser.
62
3. Stroke of thread take-up spring is too
large.
 Decrease the stroke of thread take-up
spring.
64
5. Needle thread
appears on the
wrong side of
material at
bar-tacking section
in dumpling
condition.
1. Bar-tacking thread tension is too low.

Increase the bar-tacking thread tension.
25
2. Bobbin thread tension is too high.
 Decrease tension of the bobbin thread.
(0.05 to 0.1N)
16
3. Number of stitches is large due to radial
shape

Decrease the number of stitches.
34
4. Tension at the end of sewing is too low. 
Increase tension at the end of sewing.
52
6. Stitches float. 1. Bobbin thread tension is too high.
 Increase the bobbin thread tension.
16
2. Bobbin thread comes off bobbin case

Perform proper threading the bobbin
case.
15
 Take care that the winding amount of
bobbin thread is not excessive.
27
7. Stitch skipping 1. Button hole is small in terms of the size of
presser.
 Replace the presser with a smaller one.
—
2. Material flops because of light-weight.
 Delay the hook-to-needle timing.
61
(Lower the needle bar by 0.5mm)
3. Attaching needle is wrong.

Adjust again the direction, height, etc.
14
4. Needle is bent.
 Replace the needle.
—
5. There is a burr or scratch on the blade
point of hook.
 Buff the blade top of hook. Or, replace
the hook.
—
8. Thread frays. 1. Number of stitches of the stitching is too
small.
 Increase the number of stitches of tie
stitching at the end of sewing.
37
2. Width of tie stitching is too wide.

Narrow the width of tie stitching at the
end of sewing.
37
9. Length of needle
thread remaining at
the end of sewing
is too long.
1. Width of tie stitching is too narrow.
 Widen the width of tie stitching at the
end of sewing.
37
2. Tension of tie stitching is too low.
 Increase the tension at the end of
sewing.
52