There are 2 power resistors on the main circuit board. Check both of them out of circuit. One or the other may be open. Usually the 100/200 ohm fails near the 3 large conectors shutting down the shredder - except for reverse.
The buzzer is for basket full. blow it clean with compressed air, maxell spray for pc's works well.
Clean all the sensors - top cd slot, front load slot, basket full on bottom.
Joe
August 2011