Check all the power cables (remove the optical drive carrier,..., and check those areas), as it's possible one came loose during shipping. Don't look at it and assume it's good, pull it, and reconnect (they can fool you).It happens always. No matter the CPU's, RAM, GPU are in.
When I press DIAG Button it's yellow and it shows STBY.
There's another thread, where this was the cause. So it's proof that it does actually happen to computers, even if they're Mac Pro's.Will check this out
I've tested everything right now. Even rear fan.
Heatsinks doesn't matter. It's only a temp controller.
Pull the optical bay unit out, unplug the cables, and remove the screws.I think this is it !
Cables are going into power supply and connectors cannot be properly connected to it making Mac not properly powered.
How to remove whole power supply ?
I've removed PSU, checked all connections and still the same !
The only possible way to check if it's PSU i to replace the current PSU with my working one from Mac Pro 2006.
But I'm scared. I do not want to have two dead Macs.
It looks like Mac Pro 2008 is having different power supply than my current Mac Pro 2006.