Chosen Solution
Hi I have replaced both the video card [brand new] and the screen but the problem has not gone, Is it the logic board that needs to be replaced? Any way I can confirm this? Thank you Update (05/21/2019) Hi Dan, Actually to be more accurate, after repeated rebooting the the iMac started working normally, I then did the hardware test and all passed but now after almost 3 weeks it has stopped working with the same typical 5 pink vertical lines as before, I have not connected it to an external monitor. Do I need a special cable for this, Thanks again!
The symptoms you’ve mentioned are a-typical of the common graphics fault on the 27” 2011 iMac ranges unfortunately. The cause of the common fault on this range is related to the GPU, which is removable on this range. Basically, they used lead free solder for the GPU that made it more environmentally friendly, but with the casing design on these machines holding in so much heat, and the lower melting point of lead free solder, the GPU joints would fracture. The main reason it sounds like its the common problem is because it starts out intermittent, and is most affected when the machine is hot. So the multiple reboots would function the same as leaving it to cool for a while before re-trying. The only other possible cause is LCD panel or logic, but GPU is most likely. You noted having tried a replacement GPU already, but was it a re-balled card, or one with the original lead free solder? as you cannot buy these cards ‘new’, it is likely second hand, and very likely suffering from the same fault. we only ever fit re-balled cards (not re-flowed cards) because of how common this faulty is.
