Poorly connecting video cable? No chime no Boot, LED 1-3 OK
Hello,
I own a 2011 27" iMac EMC 2429 that's been doing me great service. I love the machine and would love to get it back up running.
Symptoms:
While operating normally a small move or other caused the display to go to a pixelated line like image. Force resetting results in black screen, no startup chime and generally no love.
Partial Diagnosis:
I have opened the machine, removed the display and followed the 4 LED diagnosis without screen.
After plugging in main power:
LED 501 lights up constantly, no issues
After turning on power button:
LED 502 and 503 light up constantly, no issues
LED504:
Is dark, but obviously my screen is disconnected at this point.
On Reinserting the screen and all cables:
Mac powers up and boots normally, no issues at all.
Anecdote:
I keep my iMac on a metal stand to get it to actual eye-level height, the moment I lifted it up there, the above symptom essentially repeated itself. Now it lays dead again with a black screen.
Theory:
While I never checked LED504 for proper operation, I suppose the screen and everything working as expected settles that.
My guess is that one of the cables is loose or partly faulty, and any random move of the angle of the monitor or the whole device itself ends up disconnecting something essential, resulting in a display error during operation (pixels and lines) and the display not being present preventing startup (no chime, nothing).
Ask:
While I know that the GPU failing on this machine is very likely, I am guessing this is more of a connector/cable issue?
While I'm familiar with the 4 cables of the screen, I wonder if there is a meaningful sequence of those and or other cables to check for and replace before going full GPU replacement or trying to diagnose problems at the inverter board.
Of course, all other suggestions highly welcome.
Thank you!
Is this a good question?