Model A1200 with 2.16 or 2.33 GHz Core 2 Duo processor

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System won't boot after video card replacement

Replaced the GPU in my 24" iMac, following a number of web resources. No the machine won't boot. The pilot lamp (lower right corner) comes on, and at least one of the fans runs, but no screen backlight and (apparently) no HDD action. With the bezel removed, I have one green LED just above the memory slots, so I believe the Power Supply is OK. I've had the bloomin' thing open half a dozen times, looking for something I forgot to reconnect, but there don't appear to be any empty connectors. Any suggestions on what to do next?

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After reading through a bunch of questions & answers here, I tried the CMD+OPT+Q+R startup and, lo and behold, I got a chime, backlight, and the system looked like it was starting to boot. Went through the grey screen, to the blue one, then... blank again. Do these new symptoms point anywhere?


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Put the old chip back in.

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Swapped the original GPU back in, and things are different. Not sure they're better, but different. The system starts now, get the chime, backlight, grey screen, blue screen and a few seconds of wallpaper, then back to a blue screen, with a spinner. Optical drive won't accept a DVD, and it seems like there's no OS to be found. Too late tonight to do more, so I'll sleep on it.


First zap the PRAM, start up holding down the option, command P & R keys, hold for three tones then proceed to start.

Your machine cannot find an operating system. Boot up from your system installation disk, insert the disk and start up holding down the "C" key, go to the second page pull down menu to Utilities -> Disk Utility and see if the drive can be repaired.


Zapped the PRAM, then tried to load the install disk. The optical drive still won't load the install DVD. Any way I can install the OS from my laptop DVD drive?


Yes in Target mode as long as the laptop has an Intel processor.


To boot in Target Mode connect the two macs via Firewire cable and start the sick mac holding down the "T" key. Then start the other mac normally. The sick macs hard drive icon should show up on the desktop. I'd run Disk Utilities first then start the new mac from your system installation disk holding down the"C" key and install a system on the other mac.


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