He connects the miner with 2 pci connectors and it tries to start working, but after few seconds the power supply simply powers off.
If he simply powers up the blade with that holds the ethernet connector it works fine, but if he just tries to power up the other the power supply powers off again. The power supplly is a nox urano vs 750W. He also tried to put something on the 5V rail just instead the power supply was not balanced, but it doesn't work neither.
What can it be ?
a) The power supply
b) Broken board
c) other ?
Thanks in advance for any help
It's certainly an inadequate power supply. Seen this issue a couple of times. New power supply time, make sure it can deliver the needed amperage too. Alternatively, if you've got them lying around, use one power supply for each blade as an interim measure.