My girlfriend picked up a Nintendo 64 in a charity shop with a bunch of decent games for next to nothing. Sadly no power. I could see the reset button was jammed up so after a clean and revive I got to finding out that the power supply had bad caps. Since I still didn’t know if this thing worked I got to doing this malarkey. Video at bottom.
So to do this I hauled an old PSU out of my P4 Dell that I used happily until about 3 years ago, even though the harddrive had a head problem that made it audibly tick and bang when the head slapped the platter bearing. By the by it still works… Anyway for the N64 you need 3.3v and 12v to make it run. So a SATA connectors 12v, ground and 12v lines make that happen.

The final, completely reasonable result.

Make the PSU work

Since I needed a home test supply for my junk I bothered to put a switch on the power supply. This is actually a BTX supply which works the same as an ATX with the usual pinout but the fans blow the opposite way, so take the green wire and put a switch in between it and any black ground wire. Alternately if you have a mains switch on the power supply, just connect those wires and use that.

The Nintendo pinout

I’ve marked up the photo with where I’ve soldered it up – the bridges are horrendous but after this I hotglued the whole lot before checking that I hadn’t made any shorts with my multimeter, which gave weird readings. Well shit, I’d made the whole thing with the power supply on because I had previously wired the switch and checked it spun the fan up. The surprisingly quiet despite being caked with filth from years of my dusty, workshop like, also smoking environment.

Pinout for Nintendo 64 power supply

Does it work?

Yes, it does, it works great but don’t use solder bridges like me, it’s more of a pain in the ass than you’d expect, even though I was using lead/tin solder which wets so much better than silver/tin.

How it got done, in video form