There are a fair number of posts about GPU problems on iMacs, mostly around 2009 to 2011 models. The cooling of these systems is quite touchy and it is very easy to cause overheating of the graphics card. This causes the GPU chip to detach from the card, resulting in vertical colored bars, screen flooded with icons and finally, failure to boot as the problem progresses.
When faced with this situation, options are:
- Baking the card to restore the solder connections. This approach, when successful, can restore operation for a period of time, but is not necessarily a permanent fix.
- Reball the card through a third party facility. The GPU chip is completely removed from the card and reinstalled, usually in a controlled environment.The result should be equivalent to having a new card but at a lower cost.
- Purchase a tested card from a reliable company that deals in used Apple hardware. Prices vary but a warranty may be offered with the product.
- Purchase a compatible card on Amazon or eBay. Prices may be more attractive on these sites, but the purchaser needs to do the necessary homework to ensure the product is fully functional and compatible with the system.
In order to remove (for baking) and replace the card, the screen must be removed from the machine. This requires a fair amount of care since any fingerprints or dust introduced on the glass or screen will be a major distraction after the repair is completed and the display reassembled. Oil from the fingers is also very difficult to remove from the LCD. Latex gloves should be used when handling the screen and a lint-free cover used to store the glass. The connectors that need to be removed are fairly fragile and must be handled carefully to prevent creating additional problems. The procedure is well documented .and videos here and here for 2009 models and here and here for 2011 models provide good information.. This video has been quite helpful for removal and replacement of the video card.
Note the recommendation in the videos to replace the PRAM battery while the machine is disassembled. In a number of articles the argument is made that the batteries are not critical to machine operation and replacement is too complicated since the logic board must be removed. On the plus side, removal of the logic board allows for a thorough internal cleaning. If replacing the battery, the recommended battery is BR2032, an extended temperature variation of the CR2032..
Currently working on is a Late 2009 27″ iMac with Core i7 @ 2.8GHz CPU. The GPU is at the stage where the machine consistently hangs during boot. Given the fact that the GPU was most likely overheating for a while to get to this point of failure, it was decided to do a complete maintenance. The objectives were:
- Replace the video card – I was able to purchase a used video card with 90 day warranty from a reputable supplier
- Replace the hard drive with a 2Tb 7200RPM drive.
- Install an SSD in place of the optical drive. This drive will be used as the startup disk.
- Replace the BR2032 battery
- Thoroughly clean the case and fans.
- Clean and reapply thermal paste for the CPU and GPU.
- Install the optical drive as an external device.
There is no urgency to completing this project, other than the room the machine is taking up while working on it, This post will be updated with notes and challenges as I go through the objectives.