Hi, I have an iMac 1.83 Intel Core Duo. The screen went black during use about a week ago. Upon restart the power light is on steady, there is no chime, and the fan and HD spin up. The machine will not boot. It will not receive a DVD from which to boot. I have checked the HD and it works fine. I checked the logic board for leaky capacitors and did not see any. I was referred to look for diagnostic LEDs next to the ram chip but there are no LEDs next to the ram chip. There is one thing that looks like an LED above the ram chip but it does not illuminate. Any ideas about what else to check / replace or ways to diagnose would be greatly appreciated. Thanks!