Model A1174 with 2 GHz Core Duo or Model A1207 with 2.16 or 2.33 GHz Core 2 Duo

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Why does my iMac have random shutdowns?

My iMac shuts down randomly sometimes within seconds of booting to the desktop and won't restart unless it has been unplugged for several hours. I tried resetting smc, pram, reseating ram to no effect. I took it apart and disconnected the LVDS cable. The iMac booted and ran for 4 hours then I forced a shutdown. Plugged the lvds cable back in and booted, It shut down again within seconds of getting to the desktop. Do I need a new logic board?

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Sounds like you have a failing part or a failing solder joint. The problem is going to be isolating it. There are diagnostic LEDs to the right of the RAM slots on the logic board. We need to see what they are doing before and after it shuts off and what they do when you attempt a restart. There may be a piece of black electrical tape covering these lights, it can be removed.

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Hi, and thanks! I just booted (lvds still disconnected) to check but there are no LEDs around the ram slots. I read somewhere (don't remember where) that this model (core duo) doesn't have the diagnostic LEDs. Is there another way to narrow down this problem? Thanks again!

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No joy? Thanks, lee

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Hook it up to an external monitor to try to isolate the problem.

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Good advice +

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Screw that answer. Run Disk utility>repair disk permissions (in the applications folder) and on a regular basis (every 6 months) run Erase free space in the disk utility. It takes 45 (minimum) minutes and you want to have your fans running at a pretty good speed while it is running.

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Lee will be eternally grateful.
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