Dead PS4 - Not the power supply unit

Hi, I have just bought a non working PS4. Its completely dead. Bought a new Power Supply unit. No change. I then tested both old and new power units. Both are working. Im getting 5v from the connector on the mother board. I’m now stuck. Was going to try replacing the power management chip but can’t find a replacement. I’m new to this but am fairly confident changing stuff.

Any one have any ideas please? The console is completely dead. Nothing. No obvious signs of liquid damage or burned components.

Many thanks,