Operation Manual

45
Troubleshooting
Troubleshooting
In most cases you will be able to identify and remedy faults by checking the following.
Check whether:
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the upper and lower threads are threaded correctly
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the needle is inserted correctly with the flat side to the back
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the needle size is correct - check the needle/thread table page 22
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the needle tip and shaft are undamaged
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the sewing computer is clean - brush out any thread lint
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the hook race is clean
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any threads are trapped between the tension discs or under the bobbin case spring
Fault
Uneven stitch
formation
Skipped stitches
Upper thread breaks
Lower thread breaks
Needle breaks
Thread is caught in
the area of the
take-up lever
Faulty stitching
Sewing computer
Cause
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Upper thread too tight/too slack
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Needle blunt or bent, poor-quality needle
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Needle inserted incorrectly
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Poor-quality thread
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Needle/thread combination is incorrect
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Incorrectly threaded
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Incorrect needle system
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Needle blunt or bent, poor-quality needle
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Needle inserted incorrectly
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Incorrect needle point
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Upper thread tension too tight
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Incorrectly threaded
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Poor-quality or old thread
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Stitch plate or hook tip damaged
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Lower thread tension too tight
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Stitch hole in the stitch plate has been
damaged
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Needle blunt or bent
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Needle not correctly inserted
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Fabric was pulled
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Fabric was pushed when thick material
used
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Poor-quality thread, unevenly wound or
knotted
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Upper thread breaks
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Remnants of thread between the tension
discs
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Incorrect threading
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Remnants of thread under the bobbin case
spring
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Sewing computer fails to run or runs slowly
Repair
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Reduce/increase upper thread tension
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Use new, high-quality needle (BERNINA)
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The flat side of the shank must be to the back
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Use quality threads (Isacord, Mettler, Gütermann)
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Match the needle to the thread size
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Check upper thread threading path/lower thread threading path
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Use needle system 130/705 H
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Use new, good quality needles
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Insert needle as far up as it will go
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Match the needle type to the fabric
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Reduce upper thread tension
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Check upper thread threading path
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Use high-quality thread
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Have sewing computer checked by a specialized dealer
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Reduce lower thread tension
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Have sewing computer checked by a specialized dealer
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Use new needle
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Tighten the needle clamp screw
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Do not pull the fabric during sewing
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Use the correct presser foot for thick material (e.g. Jeans foot no. 8,
use height compensating tool when sewing over a thick seam
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Use high-quality thread
If the lower thread breaks and the thread is trapped in the area of the
take-up lever, proceed as follows:
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power switch to «0» (off)
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remove the screw on the headframe with the angular Torx button
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turn headframe cover slightly to the left, then slide it upwards
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remove remnants of thread
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attach headframe and retighten screw
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Fold a piece of thin fabric and slide the folded edge (not the raw
edges) between the thread tension discs, moving the fabric back and
forth to clean the right and left side of the thread tension
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Check upper and lower thread
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Carefully remove any thread remnants from under the spring
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Plug not properly inserted
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Power switch to «0» (off)
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Sewing computer has been standing in a cold room
033301.71.04_2014-02_Manual_B330_B350_PE_B380_EN