24" LED Cinema Display Issues...

[WillFisher]

Hi everyone, I just picked up a 24" LED Cinema Display for my 2015 MBP, I'm having several issues.

First up, the display only powers on if the Mini-display is connected first. If the USB/Power are plugged in first, the display fails to turn on.
The display doesn't allow me to change the brightness. The USB's on the back work perfectly fine however.
And finally, due to the above mentioning of the Mini-display having to be plugged in first, I cannot run the display in Clamshell mode.

Am I doing something wrong? Is the fact its mini-display instead of Thunderbolt a leading cause?
Any help will be much appreciated. This display is gorgeous, it would be incredible if it worked perfectly!

EDIT: If I run a video on YouTube and close the display, the audio will continue playing on the display but the picture will disappear. Pausing and playing as well, the audio will continue on the display, but the picture turns to black.

 

[DeltaMac]

Curious why you can't use clamshell mode?
Doesn't the display come on when both mDP and USB connections are already attached?

Test: nothing attached (except power to your MBPro, which you already need for clamshell mode), lid open, and booted to desktop
Plug in the display, both connectors.
Close the lid. Plug in your USB keyboard, and press key to wake up (or press key on bluetooth keyboard, if that is what you have)
Does display come on?

I can't say if you would be able to adjust the external display brightness - so not sure if there is a solution for that.
But, does clamshell mode work when you sequence the setup like that?

 

[WillFisher]

Curious why you can't use clamshell mode?
Doesn't the display come on when both mDP and USB connections are already attached?

Test: nothing attached (except power to your MBPro, which you already need for clamshell mode), lid open, and booted to desktop
Plug in the display, both connectors.
Close the lid. Plug in your USB keyboard, and press key to wake up (or press key on bluetooth keyboard, if that is what you have)
Does display come on?

I can't say if you would be able to adjust the external display brightness - so not sure if there is a solution for that.
But, does clamshell mode work when you sequence the setup like that?

For Clamshell it doesn't connect/wake up correctly. It sometimes needs a few attempts at connecting it before the display connects properly. I'm assuming its something todo with the display to come on.
I tried that out, and the display didn't come on, any other ideas?

 

[DeltaMac]

I suspect that you got a bum deal on a used display.
It's between 6 and 8 years old, so could be a bad power supply, or maybe the logic board.

Just a question, however:
This is unlikely to work on battery. You haven't been trying to do that without connecting to AC power, right?

 

[WillFisher]

I suspect that you got a bum deal on a used display.
It's between 6 and 8 years old, so could be a bad power supply, or maybe the logic board.

Just a question, however:
This is unlikely to work on battery. You haven't been trying to do that without connecting to AC power, right?

Yeah its starting to feel like that more and more... No I read how it has to be used on AC for clamshell.

Luckily I got it from a second and store with a 2 year guarantee. Guess I'll just be returning it for something else. Thanks
[doublepost=1481652954][/doublepost]UPDATE:
The monitor has been on and been used for the past 2 hours and has shown no sign of fault. Really odd.

UPDATE 2:
Since updating to 10.12.2 it works in Clamshell. How odd.