PC shuting down even with a good psu 750W. Phew!

[a3clay]

I recently assembled a new PC. But PC shuts down randomly esp. when I do multitasking. I have also checked my CPU temp and M/B temp. It is normal. I don't know how to solve this. Please help. The following is my pc configuration:
4 GB ram DDR3-1333
64 bit OS
i5-333CPU@3 GHz
ASROCK B75 M
HD 6670 Sapphire graphics
Seasonic 750 W

 

[Faun]

Shut down as in proper shut down or instant power cut ?

Your UPS ok ?

 

[rijinpk1]

can you try running your system without your gpu?

 

[topgear]

disconnect cabinet's power switch connector / header from motherboard. Start the motherboard by shorting the start pin header of the motherboad and see what happens.

 

[panwar29.ankit]

I had the same exact issue. I got a 650W power supply. The south bridge heat sink (not hard to find since it's the only heat sink other than the one on the processor) on the motherboard turned out to be overheating. I used a simple thermal paste and re-attached the heat sink and problem solved. Otherwise, the first thing that i would suggest is to try a different ram (has happened many times with my friend).