Chosen Solution
Computer has been solid for years. No issues. Five years ago I did a number of mods including RAM, ssd and swapped out the i3 for an i5. A couple of days ago started to notice an intermittent flicker. Flickers to dark no colour. GPU tests good from what I have been able to determine. I am assuming this has to do with either inverter or display. What I am wondering is - does the 21.5” iMac suffer the same fate as some of the 27” models where they internal connector in the bottom left corner of the display desolders and needs repaired? if not any other thoughts would be great. Thanks
This series uses an LED driver board as the backlights are LED’s Vs the older CCFL’s. intermittent flicker would more likely be GPU type of issue in this series. I would also make sure you’re not looking for a power instability issue from your outlet. Do you have a Surge suppressor or better yet a UPS? If the display dims or you get stage lighting then that would be a bad driver board. So what on the GPU needs service? Given the age of your system the thermal paste and thermal pads are worn out. I would strip the heat sink off and clean it throughly and apply a fresh coat of paste and on the VRAM chips new pads. Here’s the IFIXIT guide: iMac Intel 21.5" EMC 2389 GPU Heat Sink Replacement Here’s the needed pad material Arctic Thermal Pad You want to order all three sizes as different GPU boards RAM chips have different heights. Do take the time to fully dust out your system using a soft paint brush and a can of can’ed air.
