Upper-Thread Sensor - Bernina B 590 Service And Maintenance Manual

3.3 Upper-thread sensor

Issue:
Machine stops on its own while stitching. Upper-thread breakage message appears.
But the thread is not broken.
Possible sources:
• Regulator spring is not connected with actuating lug. Therefore the actuating lug remains idle, and the
error message appears.
• Faulty upper-thread sensor signal.
Solution:
• The signal can be tested in Service Program Test 4f (upper-thread sensor).
• Hook spring to actuating lug.
• Check regulator spring position and unwinding force
• Replace PCBA-Stitching head (RET)
BERNINA International AG
(see 4.2.8).
Seestrasse 161 CH-8266 Steckborn
DRAFT – VERSION
(see 5.11)
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