"Stop and go" - indefinitely

After power failure the system crashed and could not be re-started at all. I heard a rhythmic humming sound when I activated the power button, but noting else happened.
Now, I replaced the Motherboard with the same new one (Gigabyte GA-X48-DQ6. After installing the CPU (Intel Core™ 2 Quad Q9450) and 2GB Kingston RAM 6400 and one Graphic card, the system will start for about 1-2 seconds, shut down again, wait 3-4 seconds, start again 1-2 sec... and so on - till I switch the PS off or unplug it.
I have 4x 2GB RAM and I tried one by one, symptom remains same - the RAM should not be the problem.
I tried one by one of the two Graphic cards, and also both - still, same symptoms.
I have finally only CPU with cooler & fan, power switch, 1 RAM, 24-pin ATX plug and the 8-pin plug next to the CPU connected to the Motherboard. No HDD, or DVD, FDD is connected to MB or Power supply either.
Still, the problem persists. Start and run for 1-2 sec, 3-4 sec break, 1-2 sec power on and so on.

Any idea what could be the problem?:confused

 

is it possible you could borrow another power supply to try in it?

 

Unfortunately not...

I moved for work assignment to sunny India and the PS I have here is brought by a friend in Singapore and hand-carried to me while he was on a business trip. I tried to get such power supply locally, but was not able to find one with 2x AGP 6-pin plug and a 8-pin plug, only 4 pin power plug.

I will try to get something....

Any other idea?

 

Might be a fried processor.

 

The next thing I'd do is see if the supply will start up without the motherboard, you will need to short the green wire with a black like this-
http://www.fileden.com/files/2008/7/4/1988714/labeledwiresmall.jpg
You will have an extra 4 pins on the end of yours but the position of the start-up pin is the same.
If you try this and it's still starting stopping then you need a new PSU, if it starts up ok then you may still have a faulty PSU or it's something with the motherboard. Check and make sure nothing is getting shorted to ground, make sure there are no threaded motherboard support posts in the wrong place causing them to jab into the underside of the motherboard.