The root of the problem may actually be in the PSU, itself; however, if that has already been replaced, that is probably not the case.
If it works just fine at another residence, but doesn't at your residence, and you are using the same PSU to mains lead in both places; the issue likely isn't in the computer.
If you have plugged the computer directly into the mains connector on the wall at your residence, and the issue persists; you have a wiring issue that needs to be fixed, or there is a problem with the quality of power delivered to that outlet.
The difference is where it is being plugged-in, and you seem to have demonstrated that quite clearly.
If you have no Earthing at that outlet, it is possible that that lack is causing issues for you. Ignoring, for the moment, the fact that improper Earthing is horribly unsafe, I have seen the lack of Earthing cause some bizarre problems with a variety of equipment, over the years.
It merits your attention, if only to exclude the wiring as a possible cause.