Mac Pro randomly turns itself off

i've had this problem for almost a year now with my mac pro, mid 2013 A1289 and could not find a solution to date. It randomly and spontaneously turns itself off. The pattern is very random. I can turn it back on after a few seconds but it always die on me after a little while. My warranty period is now over and there is no apply service nearby (i have to send it through flight to the nearest service).

Few months back i claimed my warranty and send it to apple. They told me they replaced the logic board. Worked fine for a few weeks but the problem came back (by this time my warranty is over). not even the apple support on the phone cannot provide me a solution. So, i did a lot of research and try to fix it myself with help from local computer heads. I suspected overheating but the problem came even when i switch it on for the first time in 2 days. I got a 2kva voltage stabiliser and APC back ups pro 1000, didn't help. I got all my RAMS checked, all are 100% working. I removed some RAMS and switched it around to see if there's problem with the slots, didn't work. I bought an SSD drive, removed all my old HDD, installed a fresh OS, still the same problem. The only thing I haven't checked and now my only suspect to cause the problem is the power supply.

sorry for making this very long but i wanted to be as detailed as possible. I've wasted a lot of time, thoughts and money. And its hard not to feel deflated. Please, if there is anyone out there who can find a solution it would mean a lot.