Is to put all the parts in and hope it works.
But you mention there's no power button? Let's see what make, model motherboard you used as not one I've used just powers up without the power button connected and my pressing that.
As to the spark on the AC power plug. Very normal and I'll not write more about that.
I just try assemble a computer for the first time, after i finish putting everything together i just notice that the power supplies EVGA 400 N1, 400W doesnt have power button of any sort unlike the picture they put on the amazon page that i purchase,so i contact the tech support on amazon and they tell me to just plug into the power socket it should turn on by itself which did i did and notice there were a noise and saw a tiny spark between the plug from the power supply end and nothing turn on.they tell me to return power supply and get the refund ,but now im also vex over idea of that my mother board might also be damage i cant really test it till the new power supply deliver.

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