I'm using a Lancool II Mesh Performance case with the front-panel USB-C attachment. While my phone was plugged in and charging, it touched the connected headphone jack, and the computer immediately froze. After restarting, the power supply turns on for a few seconds, shuts off, and repeats in a loop without displaying anything or reaching BIOS. I tried clearing the CMOS, but the behavior continued. Could the motherboard or another component be permanently damaged?
2 Answers
Try disconnecting the case’s front-panel connections from the motherboard, especially the HD Audio cable and the front USB/USB-C headers. A short or damaged front I/O module can cause the system to power-cycle before POST. You can also disconnect the case power switch and briefly bridge the motherboard’s power pins with a screwdriver to start the PC.
You can also try a full CMOS reset: unplug the PC, remove the motherboard battery, hold the power button for about 30 seconds to discharge residual power, then reinstall the battery and reconnect power. Since that didn’t resolve the looping in this case, isolating the front-panel cables is the more likely solution.
Unplugging the HD Audio cable fixed it. The computer now starts normally, so the front audio connection appears to have been affected.