Question Gaming PC wouldn't switch ON

[TER809]

Okay so I've got this gaming PC for over 5 years now with no problems whatsoever, until now. Specs as follows:

CPU: Intel Core i7 4770k 3.5ghz + Cooler Master Hyper 212 EVO
MB: Gigabyte Z87X D3H
RAM: Corsair Vengeance Pro 8GB DDR3 1600
GPU: Gigabyte Aorus GTX 1060 (upgrade)

The PSU was the EVGA Supernova 650W 80+ Gold. Two weeks ago the PC wouldn't switch on and it seemed it had no power output. I started disconnecting one component at a time and try switching it on with no success, apart from the CPU cooler fan spinning 1-2 revs than it stops. I also did the paper clip test and the PSU fan stopped just after 2 seconds (no eco mode on this PSU).

So I figured the problem was with the power supply. This morning I bought a new EVGA 750W GQ 80+ Gold power supply and thought the problem will be solved, so I eagerly reconnected the cables to the MB and PSU and tried switching it on - but again, the PC wouldn't switch on. The CPU cooler fan just moved a little and stopped (not even 1 rev) . Tried the paper clip test on the new PSU and everything seemed fine.

Can someone please help me identify the problem? It's driving me crazy :-(

Thanks.

 

[clutchc]

Can you breadboard the motheboard outside the case? Set it on an insulated surface and connect just CPU/cooler, 1 stick RAM in required* slot, PSU, monitor to iGPU, and nothing else. Turn on the monitor and momentarily short the two pins that the case's power button would connect to. See if you get a display. If not, the board would be a likely culprit.

* some boards require a single stick of ram to be in a particular slot.