Just to expand on ck's advice, check out the carbon brushes in the motor. Theyre graphite blocks which transfer mains power to the copper segments of the motor -Theyre probably worn down. They're quite cheap parts and easy to replace. Power off, remove the back cover and locate the motor. May help if the machine is tilted at an angle or laid on its side. The brushes are at the other end of the motor from the drive pulley. The holders are plastic or bakelite and are generally held in with screws or plastic clips. Also, look at the copper segments they run on to check for burning or pitting. If the segments are burnt or damaged you need a replacement motor or a replacement armature (motor part) if you can source one. Occasionally may be a fault in the motor drive circuit board - in which case replacement of board only real option.
Check all wires and connectors generally for internal breakages - caused by movement of the wiring loom attached to the drum. Over a long period of time the wire strands inside the insulator break through metal fatigue. Although the outside of the wire appears ok the internal is open circuit. Pull on each individual wire - if theyre ok internally, they shouldnt stretch.
Check the tacho coil for breakages in the connections. The tacho coil is a small generator coil on the end of the motor which provides a voltage proportional to the speed of the motor. This voltage is fed back to the speed control module to enable the machine to check the rotation, direction and speed of the motor.
dannyboy, November 2008