[thunderchildobs]

I have a start up problem on my 2010 Dell Inspron Vista Desktop.

If I turn on the mains power, then turn on the PC straight away (holding down the on button) , for a split second there is power, the keyboard lights up, the fan on the video card starts up, but not the fans on the power supply, the power shuts down. Keeping On button press down, the power comes on, then goes off, and the cycle keeps repeating.

Now the interesting part, If I turn on the mains power, but not the PC and wait for 20-30 minutes and then turning the PC on, the PC starts / boots normally.
The PC has power during this 20-30minute period, lights on the motherboard are lit up.

I have done the following,
1) Blown a ton of dust out of PC.
2) Replaced the CMOS battery
3) Remove and reinserted all the memory / video cards.

None of this has helped.

Once the PC does start, it works normally.
All the fans work.
There has been no unexpected shutdowns or window crashes.
The PC is regularly on for 6 hours a day, guessing it is not an overheating problem.


Any suggestions?

Thanks

Brendan