Hi Vuli thank you for your answer,

It was my idea initially. I took my multimeter but when I tried to start the power supply I create a short circuit and now when I plug it there is an electric noise and the LED at the back does not turn on anymore. So i i'm pretty sure that i killed one of my PSU 

https://imgur.com/wpgvwkZ


 I continued to search but I can not find the wiring diagram of this model. Maybe I should post directly to the Dell forum ?