Reply 20 of 29, by andrea
I don't have that computer with me right now, but here's a drawing:
DO NOT TRUST THIS PICTURE BLINDLY, PLEASE RECHECK THE PINOUT BEFORE DOING ANYTHING. It's 11.30 at night, I'm tired and my eyes were crossing while colouring the pads. It should be right, but please check again before.
Basically you get the pinouts of the PCI slot and check if the pins supposed to carry 3V3 are left NC. If so then you can wire them to a 3V3 source of your choice. If you are using one of those stepdown converters as in my beautiful art piece be mindful that their output is quite noisy and might give you interference on the picture (or, at least, this happened to me). To "fix" it i replaced the output cap on the DC module (originally 220uF) with a bigger one (genuine fake sanyo 1500uF from china, but good enough for this). In a ideal world, you might want to think of building a proper filter, with chokes and whatnot. I CBA and it still works.
Another thing to be mindful of is that by doing this you will only provide power to the slot you wire, not all of them.