A voltage spike has caused the stepper motor driver IC to go bad. Under normal conditions, the stepper motor driver IC will not go bad due to voltage spikes. This problem is the result of a resistor that was not within tolerance. The supplier of the resistors bought the component from a different manufacturer. Since the parts are identical in appearance, and have the same part number, CAB and Tharo were unaware that there could be a problem. In most cases this part will work fine without ever exhibiting a problem.
Change the power supply board. The stepper motor driver IC or ICs have blown. The IC’s U2, U3, and U12 are located to the front back of the power supply board, and they are mounted to the heat sink. Resistors R1 and R2 ( .47 Ohm 4 Watt inductance free) are located near the stepper motor drivers U2 and U3. They are the large rectangular white resistors labeled in red. You may also find that the fuses SI1 and SI2 (1.6A 250V) have blown. These fuses are located at the back, and on the front edge of the power supply board. They are round and black, and may be socketed