How to control Apple Cinema Display 20" model A1038 brightness

[giambattista]

Hello,
is there a way to control Apple Cinema Display's brightness from Mac OS High Sierra running on a Mac mini 2012?
The display is an old Apple Cinema Display 20" model A1038 Clear Enclosure.
I tried to install Snow Leopard Server on Parallel Desktop 13, but the brightness cursor in Monitor preferences doesn't show up.
Furthermore, Monitor Control 2.1 utility doesn't work with the Apple Cinema Display 20" model A1038.
Any suggestions?
Thanks.

 

[joevt]

Is the USB connected? The monitor should appear in the list of USB devices.

What adapter are you using to connect the display?

Virtual machines don't have a real connection to displays.

Does AllRez show any VCP info from DDC/CI?

 

[giambattista]

Apple Studio Display #2 is connected to virtual Mac OSX Snow Leopard (screenshot 1)
Apple Cinema Display 20" is not shown anywhere.
Apple Cinema Display 20" doesn't appear in the list of devices.
It doesn't seem to be recognized.
The only display shown is Apple Studio Display and Apple studio Display #2.

The Apple Cinema Display 20" is connected through the Apple DVI-ADC adapter.
There is also a DVI-Thunderbolt cable that connects the Display to the Mac mini's Thunderbolt port.
Please note that the Apple DVI-ADC adapter also includes a USB cable connected to one of the Mac mini's USB ports.

As for your third question, "Does AllRez show any VCP info from DDC/CI?" I don't understand what it means. Sorry.