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I have a 15" LTN156HL01 Lcd display which I turned into an external monitor by using a controller board. Here's the thing:

It works perfectly on my PS4. It works perfectly with my brother's MacBook Air. It even works when connected to my Canon 80D.

But when connected to my MBP 15" the backlight of the external monitor lights up but the image is totally black. However my Mac detects the screen... even if I change resolution, the problem persists.

Then one day I tried to reboot the MBP in safe-mode and when restarted properly... Hurrah! the screen was actually working super fine. But when I unplugged it and replugged it... here we are again.. black screen.

With these test, I realized that the monitor works, the controller board works fine and that it can be used with my MBP 15". The problem is not with the hardware, it has to be related with software or OS. If not, I cannot explain why it worked that time... What can it be? How can I solve it?

Thank you in advance!

2 Answers 2

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While I'm not sure what you mean by a controller board (is it a video card or a dock?), Here's a few tips to try.

Test the cable against other cables and inputs. I recently had a mini display cable go bad when it wasn't that old.

Consider connecting the cable directly to the monitor if you are passing it through other devices (IF Thunderbolt > External HD > Monitor, INSTEAD Thunderbolt > Monitor).

You could try resetting the NVRAM which would help your mac relearn your monitor. (Command Option P R after a cold 'Shutdown'). Google this for your specific OS.

Typically, I find a black screen when the resolution of the mac is set too high for the monitor or the refresh rate is incorrect. Match what you know what your graphic card can handle to the limitation of the monitor. If the mac's display setting are vauge, there is a utility called SwitchResX that might be helpful. You can specify the resolution of your monitor and customize it with resolutions, color profiles and shortcuts. It's free to try with some nagware or feature limitations.

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  • amazon.it/gp/product/B06WVMPWHP/… this is the control board i used. I'm going to try to reset the NVRAM and see what happens as I already tried different cables. If nothing happens I'll try with SwithResX
    – Stefano
    Commented Mar 23, 2020 at 16:43
  • Nope.. Switch res X didn't work.. i tred different resolutions and modes.. Still no image.. I wonder why it worked that time.
    – Stefano
    Commented Mar 23, 2020 at 17:23
  • Ok, are you using this external monitor in addition to the MBP's monitor or is the mac in a headless state ( no screen, just the keyboard and motherboard). If headless, then its possible you will need a headless accessory. amazon.com/…
    – ECIT
    Commented Mar 23, 2020 at 18:15
  • I'm using the MBP screen + external monitor :/
    – Stefano
    Commented Mar 24, 2020 at 8:58
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    I'm also having this same issue - the monitor worked fine on my computer up until this weekend, when we plugged in my wife's new M1 Macbook Air. The monitor continues to work fine for her computer, but is broken for mine. Reset NVRAM, SVC, cleared preferences, reinstalled operating system - nothing has worked so far.
    – zeptonaut
    Commented Jan 3, 2022 at 19:34
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I had this issue occur when setting a custom ICC profile for my external monitor.

I was lucky enough that my MacBook display still appeared even though my monitor was black, so I was able to reset the ICC profile back to factory and download and use a different profile.

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