Machine fails after the thunderstorm. Remove the power supply Board, that F1 has been blackened, varistor TNR1 melt, indicating failure was caused by lightning. C5 resistance close to 0 on both ends, online check, Q1, Q2, Q3 has penetrated a short circuit, remove the damaged component replacement, acoustic test, mechanical failure remains the same, but are no longer burning fuse F1. Check carefully, Q1 s limiting resistor R20 is the way. Replacement after reboot, troubleshooting. Fax machine while using a varistor for protection, but encountered strong thunderstorms, users might as well unplug the power plug in order to prevent unnecessary losses caused by lightning strikes.