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PC only power-cycles after a USB mouse cable shorted

September 27, 2026 4 answers
Asked by MellowPine47
My cat chewed through the cable of a USB mouse, and my desktop shut off immediately afterward. Now it will not start normally: when I press the power button, the fans spin for a moment, stop, and then repeat in a loop. I unplugged the damaged mouse and all other USB devices, disconnected the computer from wall power, inspected the USB ports for bent or touching pins, and left the system unplugged for about 15 minutes. Nothing changed. Could the short have permanently damaged the power supply, motherboard, or USB controller? Is there anything else I should try before replacing components?
CMOS reset Hardware motherboard damage PC won't boot power supply twitching fans USB short circuit

Answers

CrispHarbor8
A shorted USB cable can trip the port's protection, but whether it causes permanent damage depends on the motherboard and power-supply design. The visible USB socket can look normal even if the port controller or protection circuitry was damaged internally. Try disconnecting the damaged mouse completely and test the system with only the essential components connected.
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QuietLantern31
Do not assume the motherboard is definitely dead yet. A failing power supply, a damaged USB protection circuit, or a short involving a case USB header can all produce this behavior. If possible, test with a known-good compatible power supply, and inspect or disconnect the front-panel USB cables before considering a motherboard replacement.
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VelvetRook52
Resetting the CMOS is worth trying before buying parts. Disconnect the AC power, remove the motherboard's coin-cell battery, and use the clear-CMOS jumper according to the board manual if one is available. After waiting a few minutes, reinstall the battery and reconnect power. This probably will not repair burned hardware, but it can rule out corrupted firmware settings.
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NorthPebble6
The repeated fan spin is a failed power-on self-test, so the next step is hardware isolation. Disconnect drives, add-in cards, and USB headers, then test with the motherboard, CPU, one RAM stick, and the power supply. Diagnostic LEDs, a speaker beep code, or a POST card can help identify whether the failure is related to memory, CPU, or the board.
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