If you are doing repairs involving opening up a console, a multimeter is a must-have tool. From your description, I believe the issue is with the power board. I recommend checking the caps on the power board a second time. Do any of them appear bloated, even if they are not leaking? Normally, the top of the cap should be flat. (bloated caps can sometimes be missed if they aren't leaking.)
An issue with the fuse was my first thought, but if the fuse was blown, the Saturn wouldn't be getting any power at all.