If the official service manual cannot be found:
: Mechanical failure in the foot pedal is often caused by broken wire terminals or a faulty speed regulator inside the pedal housing. Manual Availability husqvarna optima 610 service manual
Before you start any repair, photocopy or scan the "Adjustment Specifications" page. Keep it taped inside your sewing machine cabinet. That single page—listing needle bar height, hook clearance, tension spring specs, and belt deflection—will solve 80% of your future problems. If the official service manual cannot be found:
: Detailed instructions on safely removing and reattaching machine covers and internal components. tension spring specs