@an0n1mus wrote:
It's not quite clear to me what this means. Is it one of these cases:
1. The monitor is completely blank as if the machine or monitor has been turned off? Or,
2. Is it black or dark, but with a small cursor in the top left hand corner that the user can't do anything with?
In case 1, it's likely a hardware issue.
In case 2, more likely a software issue.
In relation to software, the AMD card needs to have the firmware package:
firmware-amd-graphics.
This package contains the firmware and microcode for AMD graphics. If it's not installed, install it and reboot.
You can install it from the command line without a GUI. A way to do that is to press: cntl+alt+F2, (any of F2, F3, F4 should be good) to take you to a virtual console where you can log in and install the package, as root user, with the apt command.
Code:
apt install firmware-amd-graphics
If by chance it's already installed, and the problem persists, I wonder about the "DP to VGA" adapter. They can be the source of trouble. I've had low quality ones that did not work in linux.
As for the 75Hz refresh rate, that can be set with the xrandr command.