Power supply doesn't stay on

[stupidnotdumb]

I just fitted a new Corsair CX430 PSU into my pc and connected up all the cables. When I turn it on, it turns on for a few seconds, then turns off for a few, then turns on for a few, etc.
I've disconnected everything and done the paperclip test and it seems fine.
Reconnected the motherboard and it plays up again.
Anyone know what might be wrong and how to fix it?

Thanks
Rob

Computer is a factory standard HP m9451uk with the above PSU upgrade and a geforce GTX550ti which is also new.

 

[pauls3743]

Check you connections. Have you remembered the 4/8-pin aux for the cpu, have you connected the 6-pin PCIe to the graphics card, is the 24-pin ATX connetor fully home?

Having gone through that and it still doesn't boot, try the old supply again.

 

[stupidnotdumb]

I noted down all the plugs i needed when I removed the original PSU so I'm certain I've got that right after double and triple checking.
Good suggestion to try the old unit again, unfortunately the problem remains with that one connected as well.

 

[smorizio]

see if the power supply cant handle the gpu load. try removing the gpu and see if it reboots. if it does..could have a bad power supply or a dead short in your system.

 

[stupidnotdumb]

GPU removed to no advantage.
I'm not likely to do any damage having the computer turning on and off repeatedly while I try and fix it am I?

 

[stupidnotdumb]

I have now tried 3 different PSUs and tried using different plugs around the house, doesn't seem to help.

 

[smorizio]

i would check to see that your ram is in right and there no cut or pinched wires. check your drive cables. with three power supplys and the same issue. it not the ps now..it a short or dead part. (hopfully it not a cap failure or the mb.)
check for drop screws or anything that could short the mb out to the case.

 

[stupidnotdumb]

Everything looks fine to my inexpert eye, no damaged wires and nothing touching the mobo that shouldn't be.
I guess that leaves damage as the problem. If it's the mobo (seems most likely) I assume that will need to be replaced rather than repaired? I don't know what you mean by a cap failure, would that be expensive to fix?

 

[smorizio]

i would try taking the mb out of the pc and trying to see if it post on top of a desk. (use one stick of ram and no video card if it has onboard video). if the mb still has that post no post issue. there your better off looking on ebay for the same mb (there a service part stamp on all hp parts). or take all your older parts and pick up a new case and mb/cpu combo. if a cap did fail then you need someone with the tools and know how to do board level debug (costly).