Hello
I received 27" iMac, Late 2015 model that's broken. I don't know what exactly happened but it appears to be unopened and there are no marks indicating prior repair attempts.
Initially it didn't display anything on the screen and backlight didn't work. Only 2 diagnostic LEDs would light up and 3rd was very faint. I opened it and found F4400 fuse near eDP connector to be blown. Replaced it with a suitable part and backlight came back to life. Unfortunately it still doesn't display anything on the screen. Now I get 4 green diagnostic LEDs.
I can hear the chime and also I can adjust brightness using keyboard buttons.
What I've tried so far:
I know the next logical step will be to try my iMac with an external display but I haven't received the adapter yet. Ultimately I wanted to convert it into 5K display but I thought it would be nice to fix it first to make sure the LCD is fine.
Do you have any other clues?
My iMac has 820-00134-A logic board.
I received 27" iMac, Late 2015 model that's broken. I don't know what exactly happened but it appears to be unopened and there are no marks indicating prior repair attempts.
Initially it didn't display anything on the screen and backlight didn't work. Only 2 diagnostic LEDs would light up and 3rd was very faint. I opened it and found F4400 fuse near eDP connector to be blown. Replaced it with a suitable part and backlight came back to life. Unfortunately it still doesn't display anything on the screen. Now I get 4 green diagnostic LEDs.
I can hear the chime and also I can adjust brightness using keyboard buttons.
What I've tried so far:
- replaced F4400 fuse
- tried removing coin battery
- tried booting it without Blade SSD
- tried booting it with audio jack PCB disconnected
- tried reflashing EFI with one found online, also tried cleaning ME region in the original EFI
- checked eDP connector both on the logic board and TCON
- checked main fuse and all filters on TCON module
- I get 0.9 Ohms reading on GPU coils but I assume it's okay for a GPU
I know the next logical step will be to try my iMac with an external display but I haven't received the adapter yet. Ultimately I wanted to convert it into 5K display but I thought it would be nice to fix it first to make sure the LCD is fine.
Do you have any other clues?
My iMac has 820-00134-A logic board.
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