Gateway Profile 4 PS Have 20 bad units that need...

Thought it was just a blown fuse, but no. Some have ramping problems that go from almost zero to 12 volts on a digital meter, and then drop back down repeatedly (power LED goes dim and then bright). Some have no DC output, and I had also replaced a few N channel MOSFETs that were burned out (soot evident) and attached to a thick heat sink. After replacing some of the smaller TO220 sized chips, still no DC. These are all mostly Delta ADP180 power modules like the photo. Some have a power LED and some don't. Even invested in some hard to find MOSFETS (from ST Microdevices) for these, in hopes that just replacing the chips would fix some of the problems. I do hear a 'click' (like a spark sound) when I plug in an AC cord so I know power is going in, but it never gets to the DC out end.