[Solved] Desktop shows up only with 2 displays connected (HDMI+DVI)

[imatrix]

Hi guys,

my first real mackintosh, thanks to forum I solved lot of problems and now I have stucked with weird one. High Sierra shows up only when I have connected 2 displays.
Workflow:
System starting with 4K Samsung TV via Club3D DP-HDMI adapter
Loading Apple logo, in the half of loading - blink and black screen, showing higher resolution Apple logo and loading to the end, after that only black screen. But based on the activity of SSD system is starting
TV showing only black screen
I plug into graphics card DVI with normal monitor
Screen shows properly on both displays
When I unplug DVI monitor, HDMI TV go off and screen don't come back even after plug-in in both displays, I must do reset and start system again


My build (iMac18,3 with High Sierra)
Intel Core i7-8700K@5GHz
GeForce GTX 1080Ti
Gigabyte Z370-HD3P
Samsung 960 Pro 1 TB
16 GB DDR4@3000

Thanks!

 

[BreBo]

@imatrix, please update your profile (personal details) with your Motherboard or Make/Model, CPU and Graphics Card.

Profiles need to contain at least your primary system to assist others with helping you.

 

[imatrix]

SOLVED - complete clean reinstall with Displayport-HDMI2.0 adapter from Club3D