220-1102 Question 708
Single answerElectrical safetyA technician is called to replace a failed power supply in a desktop PC located in a warehouse office. When the technician arrives, the user says the computer shut off after a "pop" sound and there is a faint burnt smell coming from the case. The technician removes the side panel and sees dust buildup around the power supply area. What should the technician do FIRST to follow proper electrical safety procedures?
- A
Open the power supply housing to inspect the internal capacitor and look for visible damage
- B
Turn off the computer, unplug it from AC power, and allow time for stored charge to dissipate before servicing
- C
Use compressed air immediately to clear dust from the power supply while the system remains connected to power
- D
Replace only the internal fuse in the power supply so the PC can be tested before ordering parts
Show answer and explanation
Correct answer: B
Explanation
In A+ Core 2 electrical safety scenarios, the technician's first action should be to eliminate the electrical hazard by powering down and disconnecting the device from AC power before servicing. A burnt smell or popping sound strongly suggests possible PSU failure. Industry best practices and manufacturer guidance for desktop service emphasize disconnecting power, using ESD precautions after power removal, and avoiding opening components such as power supplies or CRT displays because they can store hazardous voltage. In a real-world environment, the correct next steps after disconnecting power would typically include replacing the entire PSU rather than attempting internal PSU repair.
- A. Incorrect.
This is incorrect. Technicians should not open a power supply housing in normal field service. Power supplies contain high-voltage components, including capacitors, that can retain a dangerous charge even after unplugging. Opening the PSU exposes the technician to significant electrical hazard and is not an A+ best-practice repair step.
- B. Correct.
This is correct. The first priority in an electrical safety scenario is to remove the equipment from the power source and avoid contact with potentially energized components. Unplugging the system and allowing time for residual charge to dissipate helps reduce the risk of electric shock before any further inspection or component replacement. This aligns with standard technician safety practices for servicing internal PC components.
- C. Incorrect.
This is incorrect. Cleaning a system that is still connected to AC power is unsafe, especially when there has been a pop sound and burnt odor suggesting electrical failure. Even if the computer appears off, standby power may still be present from the power supply. Cleaning should occur only after the device has been disconnected and made safe.
- D. Incorrect.
This is incorrect. Replacing an internal fuse inside a PC power supply is not an appropriate first step and generally is not a field-service action for A+ technicians. The failed fuse may be a symptom of a larger internal fault. Attempting this repair also requires opening the PSU, which creates unnecessary electrical risk.