Swapping the display on MBP 15" mid-2012 (A1286) to hi-res (solved)

[Perezx]

Hello everybody!
I definitely need your help as I can't understand what's going wrong.
As you know, A1286 were sold with 3 types of displays: "standard" glossy 1440x900, hi-res glossy 1680x1050 and hi-res matte 1680x1050.
Well, I have two machines: 2.3GHz with "hi-res matte" display and 2.7GHz with "standard" display (joke of fate, yeah).
Obviously, I want to swap displays and get 2.7 machine (it has more VRAM, too) with hi-res display.
Every manual and Q&A says that this can be done easily and even the display from '2011 A1286 will fit.
Not in my case: 2.7 machine starts, but the screen remains white and blank - backlight only, no image.
2.3 machine with "standard" display works fine. 2.7 machine with "standard" display from third A1286 works also fine.

Whats going on? Any suggestions?

 

[Audit13]

The screen from the 2011 probably has a part number that is not recognised by the 2012's bootrom.

 

[Perezx]

The screen from the 2011 probably has a part number that is not recognised by the 2012's bootrom.

Both machines are mid-2012.
And even more, there are several evidences in Internet that mid-2012 machines accept screens from late-2011...

 

[Audit13]

Both machines are mid-2012.
And even more, there are several evidences in Internet that mid-2012 machines accept screens from late-2011...

Are both machine running the same bootrom?

Sounds to me like the display is not being initialised by the bootrom.

Does the 2.7 work with an external monitor?

 

[Perezx]

Are both machine running the same bootrom?

No, 2.7's BR is 228.0.0.0.0, while 2.3's one is 226.0.0.0.0.

Sounds to me like the display is not being initialised by the bootrom.

Not sure BootROM has anything in common with screen, which is GPU's responsibility.

Does the 2.7 work with an external monitor?

I don't have anything to attach to Thunderbolt socket, however, machine boots and is accessible via VNC.

 

[Audit13]

No, 2.7's BR is 228.0.0.0.0, while 2.3's one is 226.0.0.0.0.


Not sure BootROM has anything in common with screen, which is GPU's responsibility.


I don't have anything to attach to Thunderbolt socket, however, machine boots and is accessible via VNC.

I believe the bootrom does play a part based on my experience with the 2013, 2014, and 2015 13" Retina displays. The display on the 2013 and 2014 are interchangeable with each other. The 2015 display will physically connect to a 2013 and 2014 but the Apple logo will not appear and the screen remains black until the log in window where macOS has finished loading the display drivers. Same thing happens when connecting a 2013/2014 display to a 2015.

 

[Perezx]

I believe the bootrom does play a part based on my experience with the 2013, 2014, and 2015 13" Retina displays. The display on the 2013 and 2014 are interchangeable with each other. The 2015 display will physically connect to a 2013 and 2014 but the Apple logo will not appear and the screen remains black until the log in window where macOS has finished loading the display drivers. Same thing happens when connecting a 2013/2014 display to a 2015.

Hmm, sounds like an idea, however:
- I cannot downgrade BR on 2.7 machine, only upgrade 2.3 to 228 or 231 (latest one); let me guess - it will work;
- you had no bootscreen (common on MacPro with non-apple cards), but had image after the boot;
- all these displays were factory options and had to be supported by default...

 

[Audit13]

I can't really offer any other possible answers, The bootrom was often put forward as the reason my 13" 2015 display would not work properly on a 2014 13".

 

[Perezx]

I can't really offer any other possible answers, The bootrom was often put forward as the reason my 13" 2015 display would not work properly on a 2014 13".

I tried to start the machine and log on via VNC.
Well, it starts and even acknowledges it has a hi-res display. Brightness can be adjusted. And still no image

 

[Perezx]

Finally the job is done!
Display socket on 2.7 motherboard was somehow damaged: two side contacts cracked a bit, so looked like normal, but non-conductive. This broken socket provided enough LVDS lines for "standard" display, but no deal with "hi-res".
Socket replacement was a good solution