Old macbook pro display going

I have an old MBP 15" mid2010 (OS10.13.6 4 GB ram) that I use as a media server. I think the display and/or graphics unit is dying. I get a weird venetian blinds effect (black bands that slowly reveal the desktop from bottom to top) after startup and when using chrome. I don't really need to use the screen since I remote into the computer from my other computers to do my business. I would like to use it in clam shell mode but it doesn't seem to work for me, I think because I do not have another monitor hooked up to it so instead it just goes to sleep.

Is there a way to disconnect/ turn off the screen without hooking up an external monitor and still use the core of the computer as my server? Cheers