Just because that's the coolest all text smiley I've ever seen...
The PSX takes 2 voltages: 7.4v and 3.3v.
Inside it, there is a PSU with a few colored wires going between it and the motherboard. One is GND, one is 7.4v, one is 3.3v, and I have no idea what the Heck the other ones are. To find out which is which, unplug the wires from the motherboard side and turn the PSU on via the power button. Take a multimeter (if you don't have one, get one. Radioshack has some cheap ones) and put it on the voltage setting. Put the black lead on any GND point on the PSU and touch the red lead to one of the wires that goes to the motherboard. (may need to strip them to do this.) the screen will display the voltage of that line. Write it down on paper and repeat for all the wires. The spot on the motherboard where the wires went is where you solder the power wires. To get 3.3v, go look in the N64 section. You need a TI PTH08080 or 08000, a 2k ohm resistor, and a 100uf electrolytic capactior. Wiring diagrams are everywhere.
hi 
trying to find schematics for how the battery and power supply would work... I can only seem to find them for the PSone and not the PSx 
