the power supply shut down when i tunr it on.
Do you think i can fix the problem ?
if it is a Fet i will difficult to find and change.
Honest mode: With a soldering iron and some luck? No.
In order to fix boards properly you really need a good pre-heater (not a toaster oven. No. Just. No.) and a ok air rework tool (Aoyue isn't bad) and experience in using both. I've got another thread where I have been documenting all of my Neptune and Titan repairs here:
https://bitcointalk.org/index.php?topic=1283859.new#newIf you would like me to work on it, send me a PM.