Chosen Solution
My iMac late 2009 (2.66 GHz Core i5, model A1312 aka EMC 2374, iMac11,1) is not booting in regular mode. The screen breaks up and the boot stalls. It boots in safe mode with some glitches (e.g., the mouse pointer has a square grid of horizontal lines). From what I have discovered so far, this is most likely a GPU glitch. I have seen ideas like pulling out the graphics card and baking at 200°C, which strikes me as hit and miss and reballing the BGA (for which I would struggle to find a shop). Best option would seem to be to replace the graphics card, for which I can get local help (I live far from big cities). I did a quick scan through parts on offer at the ifixit store and most are for later models and only show compatibility for those exact models, though I also note that some later models ‘‘should’’ work on this one. So: 2 questions: Is this actually a GPU problem?If it is, what is my best option for a replacement (including part numbers for later models that are known to work, if I can’t get an exact replacement)? If I do go part replacement, international shipping is an inhibition on claiming on warranty or refund so it would be good to get this right first time.
There are two ways to fix this as you’ve noted baking the GPU board iMac Intel 27" EMC 2374, AMD Radeon HD 4850 Video Card Removal & Repair. It would be a gamble for me if the board fails as I would then need to find a replacement board and eat the cost. But, I do know of some shops will take the gamble. To be clear baking the board only rids the board of Tin Whiskers and some cold solder joints. The joints in question are locate inside the GPU chip as well as the mating surfaces of the GPU chip and the other components on the logic board. Clearly you can attack the logic board joints adding a bit of flux can help. Reballing only helps if the GPU solder has completely decomposed from excessive heat cycles. Using a leaded solder can prevent Tin Whiskers from being an issue. On the most part these fixed boards are still fragile! So I wouldn’t run heavy graphics on them. But this can buy you some time to save up to get a newer system. I personal recommend replacing the MXM board with a new one which gets into availability! Most of the older boards you find are from used systems so it’s a bit of pot luck. You can still find virgin GPU boards for your system, but! They go at a premium and getting harder to find! Here’s your systems GPU boards: AMD Radeon HD 4670 (256 MB) - Apple P/N 661-5314 (used)AMD Radeon HD 6850 (512 MB) - Apple P/N 661-5315 (new)AMD Radeon HD 6850 (512 MB) - Apple P/N 661-5315 (used)
