I have a power supply here that no longer consistently works in the
computer. However, it still generally works. It's an ATX form factor,
300W supply. I want to make a hobbyist power supply unit out of it,
with some additional circuitry for protections against it failing further.

Once upon a time, I relied on an old supply for powering up a project
back in college. It was ghetto, but worked. I'm trying to do something
more elegant now; the old supply required a load like a dead hard drive
or something to guarantee it'd turn on, and I was using stripped wires
to get into the supply.

I'm wondering if anybody's found any sites with projects like this. I'm
not getting a good Google response; I just get power supply vendors.
I'm thinking of just rolling one myself, but of course I'm lazy and
don't want to design entirely from scratch.

If I were to do this myself, I'd try to retain the original supply as
much as possible. That is, buy a bunch of those little plugs for the
hard drive and whatever else, and connect the supply to that. That
would let me pull the actual supply out if it ever completely roasts,
and replace it with another.

I'd then need my own power surge protection and some indication if the
thing can't supply the power. Normally I'd just trust the supply on
this, but this is for supplies that are starting to show some age. I'd
just scour the Internet for some schematics because those are problems.

To fake a load, I'm thinking of a relay to a large load, and a capacitor
or something to absorb whatever comes through for that moment when the
relay isn't activated. It would trip if there's suddenly no load, and
give the supply just enough not to spontaneously shut down. It would
also trip if the project to which I'm connecting doesn't suck up enough
power.

I was hoping to make a variable supply also, but I've never dealt with
efficiently changing voltages with powerful current. Yeah, I could just
use a pot, but that doesn't sound very elegant. I'd need a display also.