An improvement is disclosed in a brush cleaning apparatus for cleaning a major surface of a wafer and including wafer guide wheels for transporting the wafer. In particular, methods and apparatus are provided for detecting faults in circuits, devices, and systems using input control signals to generate controlled-duration, controlled pulse-width, transient power supply currents in a device under test, where said transient power supply currents are of controllable bandwidth and can be used as observables to determine faulty or defective operation. The seat body and the insertion seat are separable so that a fuse can be loaded or unloaded and the large volume is greatly reduced.