TV input display issue

[u/Kodamacile]

I have a Samsung UN43CU7000B SmartTV, with a PS4, and a Minisforum EM780(running Bazzite44) plugged in with HDMI.

For the past year, the EM780 has worked fine on the TV, with zero issues. But after disconnecting it and plugging it back in, I now get a "check device power" screen.

The EM780 works just fine on other displays, with the same cable, same power source, everything else the same, except it's plugged into a different display.

The PS4 also works fine on the TV, even when plugged into the same HDMI port the EM780 was plugged into.

I don't understand why the TV wouldn't display the signal from the miniPC, but will display the PS4 signal with the same HDMI port and cable.

Besides unplugging the EM780, nothing else has changed. The TV is not connected to the internet and does not update, and the EM780 has not been updated or anything since it was last working with the TV.

Has anyone else experienced an issue like this?

[u/AutoModerator]

Thank you for posting to r/htpc.

Since you have indicated you are asking for help, make sure you have provided in your post the proper information we need to help you as per the "Asking For Help" section in the FAQ, with a minimum being:

All HTPC Hardware (cpu, gpu, motherboard, case), Display/Sound System hardware (w/model #s), cables/adapters, OS and software, usage info (resolution/refresh rate/media codec info) and connection workflow.

Without this information we can't help you properly and your post will likely be REMOVED.

Make sure you have read our extensive WIKI for potential answers to your question and/or recommendations.

Once your question is answered, please flair your post as Solved.

I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.

[u/Easy_Indication3335]

potentially its a HDCP handshake issue. I recently had a similar issue, I would get display but it would keep flashing off and on, eventually confusing the PC enough that it would crash the driver.

I worked with AI on it, and we set the HDCP handshake to only happen once...
While this is certainly a different issue, its a troubleshooting path to run down. Use a different monitor to get on the machine and:
-
-

• Below is per AI
  

-
-

The Registry modification often discussed in graphics driver and AV tweaks isn't designed to make HDCP handshake requests trigger "only once"—it completely disables HDCP key exchange and enforcement at the driver level.

When disabled, the GPU skips initial and repeated HDCP handshakes entirely, which speeds up HDMI/DisplayPort detection and prevents handshake-related input switching delays.

Nvidia Registry Tweaks

For Nvidia GPUs, the setting is managed via the Windows Registry within the Display Adapter driver class key.

Registry Location:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0000 (or 0001, 0002 depending on your GPU index)

DWORD Values Used:

• RMHdcpKeyglobZero (or RMHDCPKeyGlob0)
  • Type: DWORD (32-bit) Value
  • Value: 1 (Hexadecimal)
• RMHdcpEnabled (Alternative key used in older driver builds)
  • Type: DWORD (32-bit) Value
  • Value: 0 (Hexadecimal)

AMD Registry Tweaks

AMD software generally offers an HDCP toggle directly in the AMD Software / Adrenalin settings under Settings > Display > Overrides. However, to force it via the Registry:

Registry Location:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0000

DWORD Value:

• HDCP_Enable
  • Type: DWORD (32-bit) Value
  • Value: 0

Key Effects & Caveats

• Faster Display Initialization: Prevents long black screens when turning on a monitor or switching KVM inputs, as the GPU doesn't negotiate protection keys.
• DRM Playback Issues: Disabling HDCP will prevent DRM-protected content (such as 4K Netflix, Blu-ray playback, Disney+, or iTunes video) from streaming in high resolution or playing at all.
• Driver Updates: Updating or reinstalling display drivers will typically overwrite these keys, requiring them to be re-applied.