Bernina 750 QE, User Manual

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166
Troubleshooting
Fault Cause Repair
Troubleshooting
In most cases you will be able to identify and remedy faults by checking the following.
Check if:
⦁ the upper and lower threads are threaded correctly
⦁ the needle is inserted correctly
⦁ the needle size is correct - check the needle/thread table page 16
⦁
the needle tip and shaft are undamaged
⦁ the sewing computer is clean - brush out any thread lint
⦁ the hook race is clean
⦁ any threads are trapped between the tension discs or under the bobbin case spring
Uneven stitch
formation
̶ Upper thread too tight/too slack
̶ Needle blunt or bent
̶ Poor quality needle
̶ Poor quality thread
̶ Needle/thread combination is incorrect
̶ Incorrectly threaded
⦁
reduce/increase upper thread tension
⦁ use new BERNINA quality needle
⦁ use new BERNINA quality needle
⦁ use quality thread (Isacord, Mettler, Gütermann etc.)
⦁ match the needle to the thread size
⦁
check upper and lower thread
Skipped stitches ̶ Incorrect needle system
̶ Needle bent or blunt
̶ Poor quality needle
̶ Needle inserted incorrectly
̶ Incorrect needle point
⦁ use needle system 130/705H
⦁ use new BERNINA quality needle
⦁
use new BERNINA quality needle
⦁ insert needle as far up as it will go
⦁ match the needle point to the texture of the material
Thread is caught
in the area of the
take-up lever
̶ Upper thread breaks If the upper thread breaks and the thread is trapped in the area
of the take-up lever, proceed as follows:
⦁ turn power switch to «0» (off)
⦁ remove the screw 1 on the headframe with the angular Torx
wrench
⦁ pull the headframe at the bottom slighty forward, flip it
upwards a bit and remove it
⦁ remove remnants of thread
⦁ attach headframe and retighten screw
Faulty stitching
Upper thread
breaks
Lower thread
breaks
̶ Remnants of thread between the
tension discs
̶ Incorrectly threaded
̶ Remnants of thread under the bobbin
case spring
̶ Incorrect needle/thread combination
̶ Upper thread tension too tight
̶ Incorrectly threaded
̶ Poor-quality or old thread
̶ Stitch plate or hook tip damaged
̶ Lower thread tension too tight
̶ Stitch hole in the stitch plate has been
damaged
̶ Needle blunt or bent
⦁
fold a piece of thin material and slide the folded edge (not the
raw edges) between the thread tension discs, moving the
material back and forth to clean the right and left side of the
thread tension
⦁
check upper and lower thread
⦁ carefully remove any thread remnants from under the spring
⦁ match the needle according to the thread
⦁ reduce upper thread tension
⦁ check upper threading
⦁
use quality thread (Isacord, Mettler, Gütermann etc.)
⦁ take the sewing computer to the nearest authorized
BERNINA dealer
⦁
increase the upper thread tension
⦁ take the sewing computer to the nearest authorized
BERNINA dealer
⦁ use new needle
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034247.71.04_2014-02_Manual_B750_EN