Q: My Sys is turned ON, the Fans are (SMPS & CPU) working some second, then after it will OFF, But the LED of Mother Board is still working, If i try to On the Power Button, it will not work, if i replug the Main connection it will same as above, IT PROBLEM IN SMPS or MOTHER BOARD? PL GIVE ME DETAILS.
A: If SMPS and CPU fans rotate for a few seconds then turn OFF, the safety features of SMPS or motherboard are working (activating auto-shutdown due to an anomaly). 1. If motherboard does not detect cpu cooler fan RPM, it will initiate auto-shutdown. Fan connector (sensor wire) may not be properly connected or it is connected to a wrong connector (system fan or chassis fan instead of cpu fan). 2. If SMPS detects an overloaded (or short-circuited) voltage rail, auto shutdown kicks-in. The overload could be due to any of the connected devices, a grounded motherboard or an improperly mounted heatsink that touches a live circuit. The motherboard LED is connected to the +5V SB (stand by) rail. This circuit is always powered as long as SMPS switch is ON or if no switch, as long as PC is plugged to AC outlet.