What should I try next to fix this?

[phisig32]

I press the power button and the computer turn on for a second turns off for a second then turns on again then off again and stops there. The issue will stop if I unplug the power supply to the CPU.

So far I have done the following
1. Subbed in a different power supply but got the same result.
2. Checked all my connections, removed video card and extra cards, applied new thermal grease

The computer just decided to turn off doing nothing special and now this happens.

Intel i7 (dont remeber the specs 4-5 yrs old)
asus p6t
gx 280
12gb g skill 10666 4x3

 

[Outlander_04]

unplug the front panel power and reset buttons

try starting the comp by shorting across the power connector pins with the tip of a screwdriver just for an instant
If it works then the case power switch is faulty

 

[phisig32]

ok tried that with the same result

Retried with a new PSU after reseating and new thermal grease no luck either. Ive plugged and unplugged everything I can think of

 

[Outlander_04]

'next thing is to breadboard it

Get the mb out of the case , and laid on a dry wooden breadboard . Connect everything as usual except the case power button and see if it starts

 

[phisig32]

alright guess I have an exciting sunday planned. Thanks for the advice. I'll report back after.

 

[phisig32]

breadboarded with the same result and tried with 2 different psu's

 

[Outlander_04]

That seems to say its a hardware error and its not the psu .

Try taking all but one stick of RAM out , and try different sticks in slot one

Also worth trying a different graphics card if you have one

 

[phisig32]

All of the components are fine. The only way the power will stay on is IF I disconnect the power to the CPU chip