Sometimes, it's not PSU problem, it's cable problem.
I remember the owner passing me a faulty cable. At times it works,
at times it doesn't, then it just spoils.
Just get some cables to test it, they are pretty cheap (if you know
how 
)
When new cables doesn't work, then you know it's other problems.
Since there's no beeps, it's highly a power problem, no power, no
booting, no errors.
