Model A1225 / Mid 2007 and Early 2008 / 2.4, 2.8, or 3.06 GHz Core 2 Duo processor

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My iMac will not load OS

My iMac will not load any os, I can hold alt and select any drive both internal and external, i can run new installation and format internal an external drives but once installation is completed and i try to boot os the progress bar goes across and it goes to blank grey/white screen.

i tried the following,

1) Switched hard drives

2)boot from external lion disk

3) changed ram

i don't think its the graphics card or sata cable because i was able to load and complete the OS X El Capitan installation.

Update (09/12/2016)

-- I've tried booting from an external HD (not the original drive, hooked via firewire and then by USB), a usb thumb drive (once with a Snow Leopard boot, then once with Lion) and of course the install disk. Displays the same behavior for all .

-- Attempted to boot in safe mode (CMD Shift):

-- --Displays apple screen with the progress bar

-- --fills the bar about 30%

-- --bar disappears and is replaced with spinning gear

-- --gear freezes, no boot

-- pulled and re-set ram in slots (not original RAM, but replaced w Kingston RAM when I got the machine in early 2008, and there have been no probs until now). Tried switching slots, tried each ram card alone in both slots.

-- PRAM Reset: CMD + option + P + R

-- SMC Reset: Unplugged for 15 seconds, plug and wait for 5 seconds, press power

It will go into single user mode, so i imagine the solution has to come from things I can do at that command line.

Please don't make me go to genius bar!

Update (09/12/2016)

After doing some indent research i found that this model has a 5 year recall/warranty on the GPU see video for details https://www.youtube.com/watch?v=QgQAtbum...

And this is what i used to repair. I now need to prevent my god core from hitting 200deg Cel or keeping as cool as possible

https://www.youtube.com/watch?v=9vPM41Zm...

I now need to prevent my GPU core from hitting 200deg Cel or keeping as cool as possible any ideas ?

Answered! View the answer I have this problem too

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How much RAM do you have in your system? You need to have a minimum of 2 GB. I do recommend upgrading to the max which is 6 GB.

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I have 4 GB, it's not ram issue I tested them in another system

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Do you have an external monitor to test with?

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Has a "?" symbol appeared during the process? It could be a faulty SATA connector.

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@mayer i dont but i gonna try it with one, why am i doing this if the LCD on the current system works ?

@supportninja I changed the sata cable but it did not correct the issue

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Hello,

How John said there are some computers that have the same symptoms and the problem is from the HD firmware, but most of them have a video card problem. 99% of time the video card is the one that is causing those problems even if they look like they are from another place. Try and find the same video card for it and change it and I bet it will work. I run into this problem with several computers and I did the same things like you first time.

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Can i use the video card from 20" iMac to test ?

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I dont really know if is the same model, but you can check by the serial no. and see if the video cards are the same. Sorry for the late answer! If you fixed your computer please let me know the way you did it. Thank you!

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I had a similar problem. I called Apple and they helped me for free since it was a problem with an update. They helped me do a disk image download from there site. It then worked great. Good luck!

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Nathaniel Mcintosh will be eternally grateful.
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