Chosen Solution
I am having a similar issue with a 2010 iMac 21.5". I can get an external monitor to work fine (I’m actually using it now). I have tried resetting PRAM and NVRAM with no success. In system report under Graphics/Displays, I can only see my external monitor connected via Mini Display Port adapter. I have tried looking at the screen with a flashlight (torch), i cannot see any forms of life. Any ideas?
Sadly, it sounds like the display assembly is gone. Has anyone opened the system yet? If not you could try checking the cable connections. Follow this IFIXIT guide: iMac Intel 21.5" EMC 2389 Display Replacement. Be careful as the cables are on the short side! Check the vertical sync cable (Step 5) and the data cable (Step 7). The data cable can be easily damaged so use extra care. Note the direction of the connection of the connector as you don’t want to put in backwards! If the cables are fully seated then its time for a new display. You may want to think this though as the cost of the display is around $800.
Some of these machines from this year had a recall on the video. Please give us the last four figures of your serial number and maybe I can look it up. The number is one the bottom of your stand.
