Chosen Solution
Here’s what the Apple book says: LED Startup Sequence LED #1 = Power available. If no LED is visible: • Verify AC source • Verify known-good AC cable is connected • Verify cable connection between AC inlet and power supply • Verify cable connection between power supply and logic board • Verify power supply LED #1 + LED #2 = Power available, and system is powered on. If second LED is not visible when power button is pressed: • Verify power button connection to logic board • Verify power button functionality • Verify cable connection between power supply and logic board • Verify power supply • Verify logic board LED #1 + LED #2 + LED #3 = Power available, system is powered on, and video card found. If third LED is not visible after power on: • Verify that MXM video card is seated properly • Verify logic board LED #1 + LED #2 + LED #3 + LED #4 = Power available, system is powered on, video card found, and internal LCD found. If fourth LED is not visible after power on: • Verify cable connections between LCD panel and logic board • Inspect LCD display cables for cable damage • Verify external video functionality, and according to result check the following items: -If external display works then verify/replace LED backlight board -If external display works then verify/replace LCD panel -If external display does not work verify/replace logic board
Had 24" iMac that exhibited the same symptoms. Diagnosed with bad logic board by respectable shop.
Hi all, I encounter exactly same issue. I’ve chance to have two of those EMC 2133 home so I already tested power supply swap, same symptoms appeared. I’ll continue to swap everything I can until can’t go any further. I’ll post again if I ever find anything that may help. Update (09/12/2019) Hi all, Video Card faulty in my case. Seems like I’m not the only one with same symptoms for this issue as I read other similar posts. Maybe it will help someone. Cheers
