my pc turns off every so often ,(couple of times a week) then restarts. i recently ( December) installed a new corsair power supply , and it seems to be working ok. i cleaned it out at the same time .is there anything else i can do ,before sticking paperclips in the cable connections. to see if the p/s
really is working.  dont really fancy that.

   any help would be great.Does Windows Event Log show anything that might point you in a direction of the problem. If the power supply was already replaced and the problem is back then it could be something else like RAM, Video Card, Hard Drive or SSD ( where virtual memory is written to drive and read back wrong causing a hard crash ), or Main Board issue. Additionally any overclocking can also be suspect so undo any overclocking you have going on and see if it behaves when not overclocked. I would also look at temperatures of components using speedfan and make sure that all looks good and nothing is roasting itself to a crash reset condition.Does it turn off or does it just reboot? It's pretty unlikely it actually powers down and then restarts on its own.Morning ALLAN. I am pretty sure it restarts itself . it hasn't' done it for a couple of days,so i cant' be certain but i will
definitely check and let you know.thanks for replying.Morning to you to Dave , i have just been trying all sorts memory-test  ram test i have found out that my PC is only showing 4 GB ram.
i know i have 12 GB 1x4gb   and 1x8 GB.=  12 GB  so i am going to check inside my PC to see if both sticks are SEATED OK .then i will try with just one stick and do the same tests .dont know if this is anything to do with the problem, but at least it is worth a GO.Hello again Dave , i have swapped the sticks i took the 4 GB out,  and put the 8 GB  in the same slot.
it now shows up o my PC as 8 GB.so i will see hoe things go. thanks again for your help i will keep you posted as to how it goes'. 
   Well unfortunately that didn't' WORK it did it again this morning. i was just checking me security antivirus/ and such nothing harmful.
and it just shut down then rebooted. very slow to reboot. so back to the DRAWING board. hope your still with me.

FrankWondering if you have a loose connection inside somewhere.

If it was my system and I had this, I'd boot the system and then gently flex a cable here or there to see if there is an intermittent connection such as the 24 pin that goes into the main board. If you gently move the individual wires that are PART of this connection and then all of a sudden it reboots on you then you might find your culprit. The other connection is the yellow and black wire 12 volt connections to main board as well as video card, very gently moving the wires while plugged in to see if you can get it to act up and pinpoint a loose connection.

There are no unsafe voltages inside the computer case its all 12 volts or less. Just never go into the power supply enclosure because that is dangerous and could be deadly.P.S.   The paperclip test proves nothing...