Black screen after Apple Logo, no other boot options work

I recently replaced the power supply on my IMac, and after everything was finished it finally booted up. After the apple logo had come up along with the startup chime, the screen went completely black, not even the backlight was on. I tried booting it into recovery mode, but it goes to a black screen... I tried booting from a disk with ML on it but it goes to a black screen... I tried booting to a USB but it goes to a black screen. I ran the automatic hardware tests with no errors and there was no black screen during that process. It only happens when I boot into my HD or anything else.

Any ideas?