The Bernina 830 sewing machine was the mechanical workhorse of the Bernina line during the 1970s and early 1980s. Many people still use these durable machines today even though replacement parts are hard to find and are very expensive. Before spending money on shipping the heavy model back to the company for repairs, try troubleshooting it at home first to see if you can find a cost-effective solution. The machine has no computerised parts, so repairing the machine at home, including replacing the motor belt, is fairly easy to do and won't take long.
Reverse the hand wheel toward you to raise the needle. Turn off and unplug the Bernina 830 sewing machine. Remove any loose objects such as scissors, pins or seam rippers from the sewing arm. Tilt the machine on its side so that the bottom plate is exposed to view. Use a screwdriver to remove the screw in the middle of the plate. Set the bottom plate and its screw aside.
Angle the machine toward you so that you have a clear view of the inside of the side panel. Use a screwdriver to remove the screw in the middle of this side panel.
Carefully pull the bottom of the side panel out toward you and down to release it from the sewing machine. Set the side panel and its screw aside. Push the wire assembly running to the motor to the side to reveal the motor assembly screws.
Remove the two screws beneath the motor set-up with a screwdriver. Rotate the motor out toward you. Note how the motor belt is threaded around the motor and its pulley. Gently pull off the motor belt and discard it.
Thread the new motor belt around the motor and its pulley assembly. Rotate the motor back into the machine. Replace the two motor assembly screws that hold the motor in place. Gently pull the motor wiring back into place. Reattach the sewing machine's side and bottom panels. Flip the Bernina 830 right side up, plug it in and turn it on. Run some test stitches to ensure that the new motor belt is working properly.
You may find V-shaped cracks in a worn motor belt, or that it may be stripped to the point where the inner threads show through.
The wires running into the motor of the Bernina 830 sewing machine are very delicate and can break easily, especially on older machines. Use caution when moving the wires during the repair process.