New PSU-Won't boot

Hi folks,

A couple of weeks ago my PSU failed. I was just reading an email and suddenly the pc just stopped. I thought I'd turned the power off with my foot, no smell, no noise, it just stopped.
I RMAd the PSU and it has been replaced by a Corsair AX850 and I spent hours yesterday installing it and trying to get it working but failed.
I have a Gigabyte EX58-UD5 mobo and 6GB of Corsair XMS3 RAM.
The PSU is fully modular and I've been trying various ways of connecting it but when I press the on switch nothing happens.
Just once it started up but I did not have the monitor connected so I shut it down and it hasn't done so since.
I have a couple of LEDs lit on the mobo but when I push the start button it does not even attempt to start. No fans start, no more lights appear on the mobo. Zero.
I wonder if it's the tiny power switch and reset etc pins but can't see why it should be them that's failed. Also there is a blue lit square button on the mobo that I believe should start the boot but it doesn't.
I'm at a loss as to what to try to sort this out. Could it be a faulty RAM stick?
I'd appreciate any suggestions as to how to get this sorted out or any way of diagnosing what is wrong.
I can't think it's the RAM as the failure was so painless and the PSU company say that it had failed completely. Could it have taken a stick of RAM with it?
If so would that cause this total failure to attempt to boot?
I feel I may have something connected wrongly as it shows no sign of life at all other than the mobo lights.

Help would be appreciated, thanks, John

I had a smilair problem with one of my older builds once. I put a new powersupply in (Aero Cool 550W), I switched the powersupply on and one motherboard led came on. I smilingly push the powerbutton on the front of the case and...nothing. After messing around a bunch with the tiny plugs for the powerswitch and led lights (they're still all connected to the FP1 connectors on the motherboard, just in a different order) then it finally came on. Maybe your problem is as simple as mine.

Hi John,

Double check all motherboard and PSU connections. In particular, many newer PSUs have voltage-sense feedback circuitry to ensure stable output voltages. This function is usually provided by means of a feedback cable that is wired into the motherboard end of the main connector. Check that if you have such a connector that you have plugged it into the PSU.

Thanks Morph. I think you might be right. When I first built the pc (14 months ago) I had a similar problem and after much messing about it was finally sorted. However I never managed to get the reset button to work.
I know that I have followed the mobo guide to the positioning of those connectors but I'm sure they are not in the same grouping as they were before.
Also, on one configuration I achieved a blue power led on the top panel. That is no longer appearing.
I think I'll get my camera from the car and post some pics of the them. perhaps someone with the same mobo can put me right.
Thanks for your input:)

Thanks for all your replies folks. I've been rapidly reorganising my table to accomodate two pcs. I've taken some pics of the mobo and in particular the power switch connector, reset and LED pins.
I can't help thinking these are wrong but , as I say, I've followed the guide in the mobo manual.
Basically the hard drive activity LED ( blue&white 2 socket pin) goes in the little box bottom left, the reset switch (purple&white 2 socket pin) directly beside it. On the top row of pins the power LEDs (1 blue& 1 white) and then the power sw (red&black 2 socket) goes next to them on the top row.
The more I look at them the more I think they were not like that before but that is what the manual says. I have a feeling that a couple of them were outside this little box but I can't be sure.
here's the pics:

This might be stupid but would a dead CMOS battery cause the problem?

It just died totally or lost contact.

No throwing things at me if I'm way off on the thought!

Mike

I don't know Mike. The battery seems to be seated ok and I do have a green and yellow LED on the mobo plus a blue light behind what I take is a start button on the mobo. Would I still have those if the battery was dead?
Here's a pic of the little front panel header pins: