Chosen Solution
I opened up my iMac mid 2011 21.5 to change the HDD to an SSD. Now all I get is a black screen after chime on boot. I’ve tried resetting PRAM, ensuring all 4 cables are seated correctly (the LVDS connection is a bit loose but is in), all 4 diagnostics LEDs come on and stay on. I changed back to the original HDD, I’ve cleaned all the dust out…but still no luck. Anybody got any other ideas? Thanks Update (10/03/2019) Oh, and I can’t see any icons when shining a torch on the screen.
Check your V Sync cable is not damaged first. Sounds like your LED driver board has failed. This can happen if you plug in the LVDS cable backwards! Take a look just below the LVDS connector on the logic board are the components burnt?
A loose connector also implies you pulled on it a bit so the connection is not tight. You may need to replace it. Here’s how to take the LED Driver board out to inspect it as well iMac Intel 21.5" EMC 2428 LED Driver Board Replacement. Compare it to the images here iMac Intel 21.5" EMC 2428 LED Driver Board If you see any burnt areas you’ll need to replace it.
