My Shuttle XPC SN85G4 is dead. When I connect the

My Shuttle XPC SN85G4 is dead. When I connect the power cord, the green light from motherboard turn on, which means there is power. When I turn on the XPC, it just for less than 1 sec and turn off. I can see that fan starts to work and stop and the green ligh from motherboard turn off. If I disconect the power cord and connect again, the green ligh is on again, but the XPC do not start to work.
I already dismount the XPC, removed the processor, rset the CMOS, removed memory, video card, clean everything but the problem persist. Does anyone has an idea or sugestion.

Thanks