I have a 680 watt power supply for my computer:
Q9650, Dual Sata Raid HD (500 gig each), 4870x2 ati, 4 gig DDR3
After a year all of a sudden my computer doesn't want to start anymore. I checked and I see a green light on my mobo but pressing power button doesn't do anything. I'm thinking (hoping?) that its just my PS unit that went bad, since from what I researched it barely meets the requirements, and it went out on me when I was playing particulary heavy game (all fans and everything was going). I also took out my video card and tried to boot up, but still nothing happened. What do you guys think?
Try to borrow a known good PSU. Or better yet, see if you can test your PSU in another working system. If you cannot do that, try to borrow a DMM to measure the voltages. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.
You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.
This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead.
It this works, repeat with the PSU connected to the rest of the computer.