See instructions for using the bobbin case thread tension weight to set bobbin tension first before adjusting any top tensions.

How do I adjust the tension of the bobbin thread? PDF
Guaranteed to fit Babylock Embroidery Machine Models:
BMP6, BMP8, BMP9, BMV10 Valiant, BNAL Alliance, BND9, BNT10, BNT10L, EMP6

Guaranteed to fit Brother Embroidery Machine Models:
PR-1000, PR-600, PR600II, PR600C, PR620, PR650, PR650C, PR655

Brother Thread Tensions PDF for All Machines