I know next to nothing about these units but the following seems to suggest there might be a couple more areas you may want to research before attempting any hardware repairs:
[post|232592]
This may or may not be of use.
[[Topic:Mac Mini Mid 2010]]
If considering doing hardware repairs to the unit, you might as well just go ahead and open it to check voltages, fuse presence, a visual inspection for damaged components/traces, cold/cracked solder joints or loose connectors. At least you are one step of most of the participants asking here.....you actually own a multimeter! lol :-)