Loses signal to TV when DP is connected

nu1mlock · July 6, 2021

Hi,

I have an issue with connecting my PC to my TV as a secondary display to play games on my couch.

TV works fine and confirms 4K 120Hz HDR VRR. However, as soon as I connect my monitor with a DP-cable (any DP-port) my PC loses the signal to my TV. TV goes black, Windows plays the "cable disconnected sound" (or rather, keeps playing "connected", "disconnected" over and over). TV is no longer visible in either Windows or Nvidia Control Panel.

As soon as I disconnect my monitor, the TV re-establishes connection and is again working with 4K 120Hz HDR and VRR.

I have tried a couple of things, like restarting my PC with/without TV connected, with/without monitor connected, both and none. Samsung claims it is not the TV's fault and it also seems very unlikely.

GPU: RTX 3080

Monitor: Acer Predator Z35P

TV: Samsung Q95T (same as Q90T with OneConnect box)

Cable: 65ft (20m) https://www.amazon.com/gp/product/B0923WRVY7/

Any suggestions are greatly appreciated. Thanks!

Edit: I have also tried lowering the bandwidth and have tried 1080p120 without HDR. I have also lowered resolution of my monitor to 800x600 and tried everything again. No difference. Doesn't seem to be a bandwidth issue?

Edit 2: I have now properly (?) tried all HDMI inputs on my TV and also tried enabling "Input Signal Plus" (which is required for HDR etc. on Samsung TVs) on them all. These are the results:

Highest possible resolution:

HDMI 1: 4K 60Hz, RGB, 8bit, HDR. Works.
HDMI 2: 4K 60Hz, RGB, 8bit, HDR. Works.
HDMI 3: 4K 60Hz, RGB, 8bit, HDR. Works.
HDMI 4: 4K 60Hz, RGB, 8bit. Not HDR. If monitor is connected.
HDMI 4: 4K 120Hz, RGB, 10bit, HDR. Only if monitor is disconnected.

Edit 3: The setting "Input Signal Plus" is what makes the TV go black. I don't know why though. It only happens on HDMI 4 and it doesn't matter which resolution. I've tried 1080p30 and the TV still goes black when I enable "Input Signal Plus" as long as my monitor is connected.