Certified Biomedical Equipment Technician (CBET) Practice Exam

A centrifuge that does not start without rotor assistance often indicates issues with the electrical components responsible for initiating motion. Bad brushes, which are components that transfer electrical current to the rotor's motor, can lead to insufficient power delivery, causing the centrifuge to fail to start on its own. When brushes are worn or faulty, they may not make proper contact with the motor's commutator, resulting in the motor not engaging until an external force (like assistance from the rotor) is applied.

In contrast, faulty fuses and loose wiring could lead to a complete failure of power delivery or intermittent operation, which may not allow the centrifuge to function at all. Inadequate lubrication typically relates to mechanical issues and might lead to increased friction, making it harder for the rotor to turn once started, but it would not usually prevent the motor from starting initially. Thus, the issue directly linked to the centrifuge's inability to start without assistance is related to the bad brushes affecting the electrical transfer required for motor activation.