2012 MBP Display Not Powering On

[meb31]

I've seen multiple threads and sites for this same problem, but their solutions haven't worked for me.

- Power on
- Apple Chime sounds and the power light comes on momentarily
- Fans and drive stay on (I can hear and feel them)
- Knowing that the password screen will come up, the machine accepts my password. I can change keyboard backlights, hear volume-change sounds, etc.
- No monitor -- completely black. And the Apple logo on the case does not illuminate.
- I was able to access the HD in Target Disk mode on my iMac, but I'm not educated enough to know where to navigate to determine the issue -- or if I even can determine from Target Disk.
- I've tried starting in Safe Mode and reseting PRAM, but still no luck.

I'm currently running Mavericks on a self-installed Seagate hybrid HD. Other than that, nothing crazy. Primary use for this machine is recreational, email, etc. I have some limited knowledge of removing the shell and navigating the internals, but I am by no means savvy with respect to Mac theory or EE.

Any insight is appreciated.

-meb

 

[DeltaMac]

You said that your screen is completely black.
Recheck that by restarting, giving your MBP time enough to get to the password login screen.
Shine a bright light into the screen at various angles. Do you see the password box, or anything else on the screen? It will be very dim, and might be difficult to see. And, there may be video elements (icons or the menubar, etc) visible, even if the screen backlight is not working. (those will be very dim, if visible at all)
The logo does not have a separate light. It is made visible when the screen backlight is on. You already know that the backlight does not come on, so no logo either.

If you have access to an external display, you could try that with a mini DisplayPort or Thunderbolt adapter. If an external works, then you likely have a bad internal screen, but your video output is OK.

 

[meb31]

DeltaMac,
Yes, I just used a light and I can see the PASSWORD cell with a blinking cursor.
Do you have any recommendations on a next step?

 

[DeltaMac]

Good so far. Your backlight is not working, but at least you have video, just no brightness.
If you take the bottom cover off, you could try checking that the internal video cable (called the LVDS connector) is seated properly. It's the big, wide cable in the top right corner beyond the fan.
Be careful, the connector is easy to damage, which would mean that you would have to replace the display assembly.
It's likely that reseating won't help, and you will need to have the display replaced anyway. The backlight is part of the display assembly.