PSU issue, stuck.... POWER GOOD signal, any ideas?

[Hicks12]

Right I moved case and I thought my PSU had died as the Power Good (PG) signal light went RED and the pc wouldnt boot, made sure it was the PSU took out the extension lead and plugged it elsewhere with a new cable and it worked OK. It started working fine again however I rebooted today and it died again, if I unplug the PSU the PG LED still stays red for hours, its pure fluke if it decides to change to green.

I have investigated further and it appears to be an issue between the PSU / GPU and my second monitor, as soon as I unplugged the mini-DP cable from my second monitor to my GPU the light went off and it boots perfectly (works fine when I plug the monitor back in if its booted, monitor and everything seem good).

Now if the PSU is unplugged and I plug in the mini displayport cable again it will go straight to RED again, tried this many times and it happens without fail. Now my DVI monitor causes no issue so I am thinking its not the GPU.

Any ideas whats causing this issue and how to fix it ? I have tried the second DP port and it produces the same result .
Any help is appreciated as its annoying having to unplug my monitor to boot!.

[Agent]

A short on the case maybe?

I'd take it all out and test before doing anything else, as your issues seem to have started after this point?

[karl751]

I take it you haven't got another computer so you can prove which party is at fault or maybe a friend?
It might be worth doing a bios update on your motherboard as it will also reset your bios. Maybe a faulty cable? Also specs of all your stuff would be handy

[Hicks12]

apologies been hectic sorting out things. I am trying to find my older PSU from my old house but unfortunately I havent found it yet however I am about to order a new PSU for a nas build of mine so if I cannot find it I will try and use this.

Very hard to identify the issue really .

Specs:

i5 2500k
Asus p8z77-i Mini itx
8gb ddr3
MSI 7950
Thermaltake tough power 675w