Few vertical lines appear quickly then goes black
This happened after I cleaned my LED backlight board and my power supply.
Before I cleaned them up, my iMac kept dying if there was any 'heavy' graphics-related job. Now, that issue is fixed(which means that I can run some graphics-related programs), but I get a few vertical lines appearing for a split second then the screen goes black.
The strange part is that it runs okay when it's in the boot stage(when the Apple logo appears, or when it gets to the boot selector, etc), but it doesn't right after it runs its OS.
Edit: I've also upgraded my CPU from i3 550 to i7 860.
Now I wonder what's the problem... Maybe the LED board? I mean since it also controls the display's vsync timing so...
Edit: I tried booting to macOS Recovery and realized that the display works(without any lines, just as clear as it should be) if the external display is plugged in and breaks when I unplug it. The funny thing is that I can replug it to revive the iMac display.
Questa è una buona domanda?