The items that I have put a * next to are new items to my computer related to the start of my issue. If I shut my computer down (off), I have to wait at least 5 minutes before I can start it again. If I try start it in those 5 minutes, the fans spin for about 0.1 seconds (serious) and then everything turns off. There's no POST, as the computer doesn't even get enough power to even think about starting a POST. Then, if I spam the power button again, it doesn't even get to the point where the fans spin (almost as if the computer isn't plugged in at all)
A shutdown also entails making changes to the BIOS that require a power-down (such as changing the OC values), extremely frustrating. If I restart my computer (by CTRLALTDEL in BIOS or "Start -> Restart" in Windows) there are zero issues with booting.
I worry that the above is not just a 'starting my computer annoyance', but will 'spill over' into more issues.
I have tried resetting the BIOS to default values, underclocking the computer, and upgrading the BIOS to no assistance. The fact that the computer doesn't even think about POSTing means I don't think it's a BIOS setting/software issue.
Any and all assistance would be appreciated. I want to explore all avenues before I begin the process of getting the three new components replaced.
p.s. If I shut my computer down, and then try start it again in 5 - 10 minutes time, it starts first time no problems.
Thank you for your reply, really appreciate it. The PSU was working perfectly before the Motherboard, CPU and RAM were replaced - do you recon that the drastic switch in core components is a configuration it is no longer able to handle?
So I did a lot of experimenting and found the following:
Unplugged the GFX card (and switching over to iGPU) as well as unplugging 4 of the 5 hard drives yeilded perfect results. I was able to boot, turn off, mess with OC values and all sorts of stuff with no issues at all.
I spent a few hours researching PSU's and the various concepts around them (these forums are great) and believe that my current Thermaltake 700W (not 750, as I incorrectly posted) 'ToughPower' PSU is possibly falling short on the 12V rail - it can only do 18A over 4 rails to a maximum of 50A - I'll be purchasing (unless you suggest otherwise) the Antec HCP 850W PSU which can do 40A over 4 rails to a maximum of 70A. As long as a I balance the rails out correctly, I should have no issues at all.
Edit: Just wanted to make sure I understand the balancing right. This review states that the rails are split as follows:
your power supply is fine for the job, its either faulty or you have plugged everything into one 12v rail. its not underpowered for your system, and the toughpower series are normally very reliable, but every manufacturer puts out a few faulty psu's. Dont go judging a brand on one failure. If you had really bad luck you could buy a faulty one off the shelf from each manufacturer, even the most expensive models.