iMac black screen on boot, chimes ok

[lunaradmin]

Hello, I am looking for possible causes for my issue and/or some troubleshooting steps...

iMac boots to black screen
Chimes correctly
Can hear hard drive spinning
Fan is running very fast
Cannot see anything (faintly) on screen
External monitor works fine (can see Apple logo etc.)

Reseated RAM, reset PRAM
Could it be a bad LCD connection or cable? What about the graphics card?
Anything would be helpful. Thanks in advance.

lunaradmin

 

[jerwin]

can you run hardware diagnostics?

Restart, press D when you hear the chime.

http://www.idownloadblog.com/2016/03/07/how-to-start-mac-apple-diagnostics-hardware-test-mode/

 

[nambuccaheadsau]

Shine a torch on the screen and see if there is anything viewable this would indicate a backlight problem. Regarding diagnostics must be a late 2013 or newer to run this otherwise you will need Apple Hardware Test. Always helps to provide Mac and operating system details.

If you need AHT, go to this link, select the precise model using another Mac, download to desktop and burn to a thumb drive. Must be a Mac and not a Windows machine.


https://github.com/upekkha/AppleHardwareTest