Question Dell Inspirion 3650 power supply fan is making a mechanical noise

[6StringJazzer]

It's not just the fan running at high speed, it sounds like the either the blade are hitting something or bad bearings. It's intermittent. The noise stops immediately if I pound on the case, but eventually starts again. (That doesn't sound like bad bearings to me). I opened the case and cleaned and tightened everything up once but the noise came back. I fear that there is something misaligned and vibrating inside the PSU and I am not experienced enough to crack it open and avoid getting zapped by a hot cap.

This is an old machine so if the only answer is to replace the PSU I'm just going to replace the whole machine.

(I have built my own desktops but this is wife's that we just bought off the shelf at Best Buy or Micro Center, can't even remember where.)