Chosen Solution
Hello, My 2017 iMac 21.5” 4K does not show pictures on display any more. It powers up with the chime but shows nothing on the display. It is not a backlight issue. NVRAM clear and SMC reset were tried but no luck. I can login remotely using ssh. If I try screen share, it only shows black desktop on a remote computer. An external display does not show pictures either. But I am not sure if the USB-C to HDMI dongle is recognized. I opened it up to see the diagnostic LEDs and I see that 3 LEDs are lit. I replaced the button battery with a new one but no luck. I also replaced thermal paste on the CPU, GPU and VRAM but no change (which is expected). So my question is that is there any way to run hardware diagnostics remotely? If not, what’s the next move I should take? Thanks, Tatsuya Minami
Sadly you’ve already got the needed info. If an external display won’t work as well then the issue is within the logic board GPU logic. Using any remote desktop service (SSH in this case) doesn’t use the systems GPU which is why it worked! This could be a simple issue or it could be a blown GPU chip which would require a new logic board. You’ll need to find someone with the very deep skills to fix your logic board or you could just replace it.
