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

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iMac 2211 3,06 with Nvidia 8800 fails to boot

Hi everyone,

Since a few days my iMac hasn't been feeling too well. I don't know how it happened, shut it down on Thursday and it failed to boot up on Saturday.

At first: when you started the iMac screen went black (you could see the backlight on), you heard the chime, 2 seconds of nothing, chime, 2 seconds pause, chime, ... No white screen, no logo, no nothing.

Now (after trying smc and pram reset), it's similar but different. Now it starts, you can see the screen lighting up, chime, white screen with logo, circular thing moving (I can also head the hard drive reading, normal sounds no "ticking"), and when it's about to enter OSX it restarts by itself.

At some point in time I also got a message that my iMac has been restarted or something, only seen it once.

After this and some reading on the web, I opened up the front to take a look at the indicator LED's. As far as I can tell they're all good (all green).

I also tried booting off a CD (linux), it showed one line of the starting up screen, then it stopped, hung, and showed one single red rectangular box (1 letter size) on the screen.

I tried booting of the snow leopard install USB stick I got, this also hung and auto restarted.

At times (not always, but probably around 50% of the time) when powering it up, as soon as the white background shows, I can see a somewhat distorted (should be white but has random pixels in it) line spanning the entire width of the screen, it's probably about 0,1-2mm thick and is always situated at the complete top of the screen.

I was guessing it's the videocard (nvidia 8800), but I'm not sure because the LED indicates it's good.

Initially I thought it was the HD, you know it's always the HD, and after 6 orso years not surprising, but I should be able to boot of USB/CD when it's the HD, no?

Thoughts? Comments? Suggestions? Everything is more then welcome.



PS: also tried booting with 1 memory module (normally uses 2x2), but no difference.


Added 2 pictures taken in verbose mode

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Update 27/2, since the status leds appear normal I'm attempting to remove the HD; got the tools to have it removed in the past few days, and got the HD out tonight, I'll test it tomorrow and will update after

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I fixed this yesterday, it was the graphics card all along.

Fixed this by

- disassembling the machine,

- taking out the video card,

- took off the cooler,

- cleaned up old thermal paste

- stuck it in the oven for 10 minutes on 200 ° C (385 ° F)

- let it cool down easily

- assembled everything back together

Got myself a working iMac afterwards, like nothing happened... had to reinstall OSX because I zero'd the hard drive, but still, works like a charm...

So it was the video card, even with all status leds green.

Anyway glad I got around it, thank you for all the help, and the guides ofc.

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Wow! Exactly what I experience, will follow your advice! Which instructions did you use for the disassembling? Thank you!

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Do you have an external monitor which you can connect to your system? See if that is able to work.

If you don't take a flashlight and shine it at the display at an angle after your system has booted up. Do you see a faint image of your desktop?

Let us know what you find.

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Thank you for your reply,

I have an external monitor, it was connected until I had the issues, then I removed it (didn't get any image on it at the time), but maybe that has changed after pram reset, I'll give it a go tonight.

I'll also try the flashlight thing, thanks for the tip. Will post back after testing both.

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Didn't have time to check it yesterday, it's on my to do list for tonight.. sorry about the delay

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So tested this last night:

- external monitor stays black, but I think it only lights up after OSX loads the desktop, so I figure because it's stuck starting up it never gets to the point where the desktop loads.

- using a flashlight i didn't see anything on the external, and i only saw the white startup screen with circle turning on the main display. Only this until it restarted (automatically)

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Starting to sound like a HD or power supply issue.

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Tried booting without HD installed, same thing, tried booting off USB with not HD installed, same thing, tried booting with new HD installed, same thing... dont think it's the HD... my money would be on graphics card or motherboard at the moment...

any thoughts/ideas?

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