Necchi L234A Instruction Manual page 25

Lower looper thread is too tight
The lower looper thread is unbalanced when
it is pulling on the wrong side of the fabric.
Loosen the thread tension of the lower looper
or tighten the thread tension of the upper
looper.
Left needle thread is too loose
If the left needle thread is too loose, tighten
the thread tension of the left needle or loosen
both looper threads.
Left needle thread is too tight
If the left needle thread is too tight, loosen the
thread tension of the left needle.
Right needle thread is too loose
If the right needle thread is too loose, tighten
the thread tension of the right needle.
Right needle thread is too tight
If the right needle thread is too tight, loosen
the thread tension of the right needle.
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