Screen turns on and off repeatedly not allowing me to use the laptop

First thing i would do is see if it works into a monitor. If it does not display to a monitor then you can narrow it down to more trouble shooting. Its going to be a hardware related issue in any which way. Also try tilting the screen back and forth while it is turned on to see if its bad lcd cables when they move. If neither of those easy trouble shooting steps give you any info the next thing i would do is open it up and make sure everything is connected. Your wifi card, lcd cables run through the lcd and onto the motherboard through a wifi card. Usually a small black and white cable that is connected ontop of a square card. Next thing i would do is see if your power button is on a daughter board and not attached to the motherboard. If so just buy the part yourself. Im not sure why the repair shop would have repaired it like that. I would never at my store. It seems a little sketchy.