Funny if they cannot find the problem in repair shop. Same words than Coldfire said.
Good sign if there are lights anyway. Memories you can check also so that you put
only one stick in closest to processor and try. Or if you have other memory, try with them.
Google shows that this mobo has had memory problems. I still doubt
the processor goes cooking in 1 second and hangs but cannot be sure of course.
They don't easily break today though. One way to try is turn cpu fun round
blowing other direction. 500 W hmm maybe enough. I would doubt that also.
You have maybe old pwr supply left, I would use temporarily both of them
to check if 500W is enough. But if you are unsure how, forget my words.
Good repair shop finds the problem quickly. Good luck.