Rumba with ATX power supply problem

Hello all

i've bought the REPRAP Rumba board one month ago, following the instructions on [reprap.org]
i've tried to use the atx power supply, when the jumper is on the "stand alone", the Rumba board does'nt work, the blue led is off, it's similar at no power supply.
when i disconnect the atx power supply and i move the jumper to "usb power", the board works, the blue led is on.

i've also upload the marlin-marlin v1 firmware to see if it will resolve my problem, but nothing, the board want not to work with atx power supply.

Anybody could help me what it's happens?
where can i find any informations for the atx power supply wiring with the Rumba?

Many Thanks in advance
have a nice day
Geekololo