No POST After Lightning — Check Motherboard Capacitors
A technician is troubleshooting a desktop computer that failed to boot after a lightning storm. The computer powers on (fans spin, LEDs light) but there is no POST and no beep codes. The technician has already tried a different monitor, reseated all RAM and expansion cards, and tested the power supply with a multimeter (all voltages within spec). Which of the following should the technician check NEXT?
Quick Answer
Once you know a power surge event, like a lightning strike, has occurred, the diagnostic priorities shift, because surge damage tends to concentrate in the components responsible for regulating and delivering power on the motherboard, particularly the voltage regulator modules and their supporting capacitors. The symptom pattern here, powering on with fans spinning and lights lit but no POST and no beep codes at all, indicates the system never even gets far enough to begin its startup sequence, which points toward a fundamental failure in power regulation or CPU initialization rather than a peripheral or configuration issue. The technician has already tried a different monitor, reseated RAM and expansion cards, and confirmed with a multimeter that the power supply's own voltages are within specification, which rules out both a display problem and the PSU itself as the source. That leaves damage further downstream, after the PSU delivers power but before it is properly regulated for the CPU and memory, and bulging or leaking capacitors are the classic, physically visible sign of that kind of surge damage. Whenever a system fails to POST or beep at all following a documented power event like a lightning strike or surge, and the power supply itself has already tested clean, a visual inspection of the motherboard's capacitors for bulging or leaking is the appropriate next step.
⚠ Common exam trap
It's easy for candidates to assume a working PSU (confirmed by multimeter) means the motherboard is fine, but the 220-1101 exam tests the understanding that motherboard capacitor damage can cause a 'power-on but no POST' condition without any beep codes.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check the motherboard for bulging or leaking capacitors
After a lightning storm, a power surge can damage the motherboard's voltage regulator modules (VRMs) or other components, often indicated by bulging or leaking capacitors. The symptoms—power on but no POST and no beep codes—suggest the motherboard is not initializing the CPU or memory, which is consistent with capacitor failure. The technician has already verified the PSU output and reseated components, making motherboard damage the most likely next step to check.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Check the motherboard for bulging or leaking capacitors
Why this is correct
A lightning surge can damage motherboard voltage regulators, leaving capacitors bulging or leaking. Since the PSU tests within spec and RAM, cards and monitor are eliminated, the board itself is the remaining suspect; visible capacitor damage explains power-on with no POST or beep codes.
- ✗
Replace the CMOS battery
Why it's wrong here
Replacing the CMOS battery only preserves BIOS settings and the real-time clock; a depleted cell typically yields a checksum error or lost time, not a total absence of POST. It is tempting because it is a cheap, common first step for boot faults, and would be correct if the system posted but reset its date and configuration each time.
- ✗
Test the surge protector
Why it's wrong here
Testing the surge protector cannot restore a board that already receives in-spec voltages; the multimeter reading confirms power delivery past it. Surge protectors are sacrificial devices worth verifying when a system is completely dead, but here the PSU outputs correctly, so the fault lies downstream on the motherboard or CPU.
- ✗
Reseat the CPU
Why it's wrong here
Reseating the CPU cannot restore a board whose power-good signal never asserts, because the fault lies in the motherboard's VRM or chipset, not the socket contacts. It is tempting since CPU reseating fixes bent-pin or poor-contact no-POST faults, and would be correct had the board shown any POST activity or beep codes.
Go deeper
Related to this question
Learn chapter
Power Supply Units and Connectors
Key term
RAM
RAM (Random-Access Memory) is volatile computer memory that temporarily stores data for quick access by the CPU.
Key term
Dual In-line Memory Module
A Dual In-line Memory Module (DIMM) is a small circuit board that holds memory chips and plugs into a computer's motherboard to provide Random Access Memory (RAM).
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Same concept, more angles
2 more ways this is tested on 220-1101
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A technician is troubleshooting a desktop computer that fails to boot after a power surge during a thunderstorm. The computer's power LED illuminates briefly when the power button is pressed, but then nothing happens. The technician has tested the power supply with a multimeter and it outputs correct voltages. Which of the following components is MOST likely damaged?
medium- A.CPU
- B.RAM
- ✓ C.Motherboard
- D.Hard drive
Why C: (Motherboard). Even though the power supply outputs correct voltages under multimeter testing, a power surge can damage the motherboard's voltage regulation modules (VRMs) or power management IC, preventing the system from completing the POST sequence. The brief power LED illumination indicates the PSU is functional, but the motherboard fails to sustain the boot process, which is a classic symptom of motherboard damage from a surge.
Variation 2. After a power outage, a desktop computer will not power on. The PSU fan does not spin, and no LEDs are lit. The technician tests the power supply with a PSU tester; all voltages are within spec. A multimeter reading at the motherboard's power button header shows 3.3V when the button is pressed. The power supply is also confirmed to work when tested in another system. What is the most likely cause?
hard- ✓ A.The motherboard has failed
- B.The power supply is still faulty despite the tester showing good voltages
- C.The power button is faulty
- D.The BIOS has become corrupted
Why A: The motherboard has failed because the PSU passes all voltage tests and works in another system, yet the desktop shows no signs of power (no fan spin, no LEDs) when connected to this motherboard. The 3.3V reading at the power button header indicates the motherboard is receiving standby power and the button is functioning, but the motherboard is not completing the power-on sequence (pulling PS_ON# low) to start the PSU. This points to a failed motherboard, likely a short or damaged power regulation circuit.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1101 exam.