[SOLVED]pc power supply issues (i think)

Hello everyone,
So I'm almost finished with my first reprap build. I have the sanguinololu soldered and sprinter uploaded with all the steppers and endstops in place. I was just about to start my first test run when I tried to connect one of the steppers to see if it would work... and it didn't, nothing happens. I thought that it might be the power supply so i bought a new one and it still wont work. I'm using the 4 pin 12 volt connector, but when i put a multimeter across the +12 and ground pins, it only shows about 2.25v. do i need to add a load to other pins on the power supply to get it to work? could it have something to do with me using the A4988 drivers with sanguino 1.3a since i now have 2 100k pullup resistors? I didn't think that would make much of a difference. Any help would be appreciated.
Thanks!

Edited 1 time(s). Last edit at 11/27/2011 07:23PM by ElMatador.

I should also mention that I tried this with a brand new pc power supply. My soldering looks to be pretty decent (no shorts and fairly clean). Although when I just measure the voltage of the 12v connector with no load I get 0 volts. I really hope I didn't ruin the electronics or something.

Ok, I need to start looking a little harder before posting. I didn't realize that the sense pin on the 20 pin connector needed to be grounded.

You will also need a load on the 5V line. The electronics don't load the 5V line enough to stabilize an ATX supply. Use some power resistors or lights to load the 5V line to at least an amp or two. (12V 50W accent lights are easy to come by but more expensive than a 5W resistor. )