[ 1. Fan turning in PSU.
  2. Under the load of the motherboard, all power supply voltages/signals as expected. ]


So we know that the power supply is working.

That means that the motherboard is faulty. And because the voltages/signals from the power supply are as expected, we know that the motherboard is not faulty in a way that overloads the power supply.

What Now?

We have eliminated the possibility of shorted capacitors on the motherboard.
Therefore, based on history, the most likely cause of motherboard failure is now:

* Faulty RAM chip (or chips) in bank 0
* Faulty BIOS ROM