I have generic PSU which doesn't have a seperate on off Switch and is connected to the wall socket. When I turn on my pc, it sparks where the Power cable is connected to the CPU/PSU. After starting the pc it shutdowns automatically after a while sometimes within an hour ,sometimes after 2_3 hrs even connected with a UPS, for voltage fluctuations. I don't know what's the reason? Is it the psu Or the cable or the UPS(battery is old 2 years approximately).