act 2:
I unplug and reconnect all connectors at least 6 times see more still no boot.
I check all the tensions that happens to the CPU card: they are all good so I tell myself the problem comes from the CPU card as it is she who manages the boot. I disassemble to check a component that would have taken heat and I do continuity tests without convincing results ... to the point where I am I take out the soldering iron and I redo all the welds of the components of the bottom of the cpu card (the top I am not equipped for then I did not feel to touch the processor + complex IC ...)
I reinstall the whole thing. I turn on the machine and it boot !!! so cracked weld \ dries somewhere after I could not really say where ...
sorry i m french i use google translate i hope you understand