if new needle does not help you wil have to check bobbin tension,take bobbin case and bobbin out of machine and thread per normal,let bobbincase hang on thread and shake lightly,bobbin case should move approx 20mm,if not loosen or tighten tension screw
johan
February 2014
take the needle out and draw it across the back of your hand on both sides of the needle. if one side catches then the needle point is burred which will catch the thread underneath.
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