Initial startup then shutdown
Mid 2007 Intel 2.0GHZ iMac
I have a mid-2007 2.0GHz Intel iMac that would not start up. I could hear the hard drive start up, and the fans come on, but no chime and a black screen. After reading posts about possible bad RAM I put in a new RAM chip. Made some progress as the iMac would initially try to start - grey screen with Apple logo, and then a spinning wheel, but NO chime. After about 10 seconds of trying to make it through the bootup, it shuts down. Tried resetting the SMC and zapping the PRAM - no luck. I also read posts about checking the diagnostic LEDs - where are they? Do you need to "crack" the case? Any ideas on what else I can try?
I've used iFixit a few time to take apart various systems, so I'm not afraid to do anything. If I need to test the power supply pinouts, or even swap the power supply, I'll try it. I'm just hoping it's not the logic board - that kind of gets into a "cheaper to buy a new computer" realm. This is a great site though!
Well, my problem is solved. It ended up being a corrupt hard drive. After swapping out RAM and hooking up an external hard drive, it started up normally, albeit without the chime. Disk Utility saw the internal drive, and when I tried to repair the hard drive, it came up with up severe "unrepairable" problems. I reformatted the drive and reinstalled Leopard and now the machine is up and running. I also zapped the PRAM and now the chime is back again. Glad it wasn't power supply, or worse, logic board. Thanks for the info.
If you can't come to any other conclusion than the logic board, check out the links below. I have a macbook pro 15" that displays the characteristics they talk about. You can hear it start for about 2 seconds, than it shuts down with no boot up. I am going to try this tomorrow. You basically bake the logic board to "soften up" the solder connections that may have broken loose. Be sure to pay attention to the part about the thermal paste.
Here is a blog with some good info:
There is also some good info on YouTube:
Visit ifixit.com for instructions on how to remove your logicboard.