Chosen Solution
Hey guys, My imac won’t start up. When I press the power button I can hear the hard drive and the fans working but no chime. I’ve checked the RAM, by replacing. When I took off the LCD to determine if the failure is related to a faulty LCD, I powered up the machine without the LCD connected. This resulted in blowing the fuse. The diagnostic LEDs 1-3 are lit. Has anybody a clue on that? Mit freundlichen Grüßen Andre. Update (12/03/2015) I replaced the ram by a certified one. That should be fine. But still the same behavior.
If you get no picture (black screen) the 3rd system LED is lit. No sound (chime). Fans kick on and second system LED is lit. Then it is most likely your main board that has gone bad. If it was the LCD, you would still get your chime. If it was the HD you would still get a picture, usually to black and white pring of apple logo or a flashing folder with question mark. Bad RAM you still would get a picture. Bad power supply no LED’s, fans or HD powering up.
