my corsair tx850 PSU
 

for some time now i have been having a tough time with my psu.it powers the board and but does not boot the system.sometimes it does.today it didnt even come on at all but after i left it for some hrs it came on again.it was actually fixed one time when the my enginner said it had heat problems.what advice can u give me and what other brand of psu can i invest in asap.