Beisler 739-23-1 Manual - Manual (Page 17)

2.10 Adjustment of bobbin thread tension
Caution: risk of injury!
Switch off main switch.
Never adjust bobbin thread tension while the main switch is on.
The required bobbin thread tension must be generated by means of
tension spring 5.
The brake spring 1 must be fully reset.
Adjustment of tension spring
–
With full bobbin, the bobbin case body 2 should slowly fall down
due to its own weight (see figure to the right).
– Adjust tension spring 5 with regulating screw 4, until the required
tension is established.
1-17
2
4 5
1
3