Electrical Troubleshooting — real-world interview & field troubleshooting questions with clear, practical answers. Tap any question to open its answer. Showing the first 70 questions free. The complete question bank is available as a PDF below. Main Power, Breakers & Distribution Q1 The main breaker trips immediately when a machine is energized. How would you find the fault? Answer I would isolate downstream feeders and check for a short circuit, earth fault, damaged cable, or faulty load. I would inspect the wiring, test insulation where appropriate, verify breaker size and connections, and reconnect sections one at a time to identify the faulty circuit. Q2 The incoming voltage is normal, but one panel has no output. What should you check? Answer I would check the panel incomer, isolator, fuse or breaker, busbar connections, and control supply. Then I would measure voltage at each stage to find where the supply is being lost. Q3 A three-phase machine receives voltage on o...

CNC Machine Troubleshooting — real-world interview & field troubleshooting questions with clear, practical answers. Tap any question to open its answer. Showing the first 70 questions free. The complete question bank is available as a PDF below. Power, Control & Startup Q1 The CNC machine does not power on at all. How would you troubleshoot it? Answer Check the incoming supply, main isolator, breakers, control transformer output, E-stop chain, and control fuses. Verify voltage at the machine terminals rather than only at the panel. If the supply is healthy, trace the control-power path through safety relays and contactors, then repair the failed connection or component and perform a controlled restart. Q2 The control powers up, but the CNC screen remains blank. What should you check? Answer Confirm monitor power, display cable connections, control boot sequence, and the control cabinet power supplies. Look for abnormal fan/HDD/SSD activity or diagnostic LEDs. If supply vol...