Diagnostic lights and no screen issue
I have a bit of an issue.
I’m experienced technician, but this was first 2017 5k 27 inch imac I was repairing at the component level.
Problem was that there was no image output. Tried external usb-c, no chime, no logo, but fans work.
I had previously repaired earlier 2015 imac with same fault, but found failed EFI , so I fixed it by replacing EFI chip. So I done it this time also. Bought a preprogrammed EFI chip for this particular logic board, soldered it on, tested connection - soldered great with solid connection.
Powered on - and issue is still here.
Then I noticed that only first two diagnostic lights light up. Now, does this mean that actual GPU might be fried? I know older imacs and macbooks had these issues, but new ones?
I work in university as technician and they will not approve the entire logic board replacement, and quite frankly I was saving this iMac from getting binned.
Any ideas? Suggestions?