Monitor only works if second monitor is also connected

[John6942]

Just got a GMKtek Nucbox G3 mini-PC with an N100 CPU, UHD 730 graphics, and dual HDMI outputs. It came with Windows 11 Pro pre-installed, but problem also occurs with clean Win 11 24H2 install.

This PC has an odd graphics problem that I've never seen before: One of my monitors only works when a second monitor is also connected.

Monitor 1: Vizio 4K TV
Monitor 2: HP 24" LCD monitor (from old desktop computer)

The LCD monitor works by itself, and the TV and LCD monitor work if both are connected.

But if only the TV is connected, it acts as if there is no signal from the PC. Hard to say if there really is no signal, or if the HDMI output is in a format the TV can't process -- I don't have an oscilloscope or HDMI bus analyzer to check it.

The TV works by itself during UEFI boot, with the basic VGA driver in Windows 11. But it fails as soon as Windows Update installs the Intel UHD drivers.

It doesn't matter which HDMI ports are used, or which cables (I've tried all combinations).

Does this sound familiar to anybody?

[n_scott_pearson · Accepted solution]

This doesn't strike me as being a driver problem. Have you tried accessing BIOS Setup with only the TV connected? If this doesn't work (either), then it's definitely a hardware/firmware problem.
In either case, I suggest you contact the manufacturer. Don't be surprised, however, if there's nothing they can do about it.
Sorry,
...S

[John6942]

Have you tried accessing BIOS Setup with only the TV connected?

Yes. UEFI setup works OK. TV also works by itself with Ubuntu 24 Linux. Only fails once UHD drivers get installed on Windows 11.

... I suggest you contact the manufacturer. Don't be surprised, however, if there's nothing they can do about it.

My only real hope was that somebody might recognize the problem. I don't expect the vendor to be able to troubleshoot or fix it.

Looks like I'll be sending this mini-PC back for a refund.

Thanks for the response.

[KhanSeries13]

GMKtek Nucbox G3 mini-PC. Based on your explanation, this does sound like a graphics output compatibility issue im not sure but, likely related to the Intel UHD 730 drivers or how they interact with your TV

Since the issue only occurs after the Intel UHD drivers are installed, try either updating to the latest graphics driver directly from Intel's website or rolling back to an earlier version to see if that resolves the issue... Right-click on the desktop, select Display Settings, and see if the TV is being detected properly when it is connected alone. You can also try adjusting the resolution or refresh rate settings, as the TV might have issues with certain formats.

Try Disabling "Fast Boot". In some cases, "Fast Boot" can cause issues with monitor detection. You can disable it in the UEFI settings and see if that helps. The fact that both monitors work when connected together might suggest that the TV is not properly recognized when isolated. Check if there are any settings in the Intel Graphics Control Panel that might be affecting output behavior, such as the HDMI signal or display mode. Some TVs have specific HDMI modes (e.g., PC mode, HDMI 2.0/1.4 settings). Ensure that the TV is set to the correct input mode for use with a PC, as some TVs may not automatically detect the signal format from a PC.

If you’ve tried all these steps and the problem persists, I agree with @n_scott_pearson we suggest you to contact your device manufacturer