Question Computer won't POST unless HDMI cable is unplugged ?

[provoteriat]

The 9 year old Nvidia graphics card has 2 cables connected to it. One DVI going to the monitor, and an HDMI cable going to an AV receiver/amplifier.
The computer was working fine for past 6 months, and this is recent.

Once I unplug the HDMI, I go ahead an plug it back in, after the computer POSTs.
I log on to Ubuntu 22.0 LTS, and it doesn't notice the HDMI interface at all.

There's no option to 'mirror' the display.
If I wish to have sound, I now have to resort to connect an optical cable from the motherboard to the AV receiver.

BIOS was already 'flashed', for the sake of being able to use an M.2 pci for booting to OS, as future upgrade, which I have yet to utilize.

System specification:
Intel 4670K Haswell
Asus Z87 Plus w/UEFI compatibility
Nvidia GeForce 760
G.Skill Low Cas Latency 4x32GB
Sandisk SSD

Edit: I unplugged the DVI and then plugged the HDMI directly to the monitor, then change mode on the monitor from DVI to HDMI, and computer is able to boot.

Also, I unplugged the AV from the electrical power outlet with DVI plugged in, and the computer refused to post. I then unplugged the HDMI cable from the AV and computer was able to post.

I guess the next step would be to go an AV forum and make my way up from there.

 

[Lutfij]

You forgot to mention the make and model of your PSU and it's age. It might be that your AV receiver might be triggering a grounding issue, perhaps try and locate your gear to another wall outlet.

 

[provoteriat]

It seems the culprit of why Ubuntu not recognizing the HDMI port (after plugging it in after POST) for audio usage, was due to Secure Boot setting in the UEFI-Bios as pictured. I had to change it from Windows to 'Other OS'.

Also display is successfully mirrored.

Unfortunately, this still requires me to unplug the HDMI cable then plug it back in after POST.

PSU was bought used in 2022 for $40 shipped. A Thermaltake 80 Plus 500w,

Also I'd like to add, that if the HDMI is left connected and the computer refuses to POST, I can unplug the HDMI, the plug it back in, AND then I must press the power button on the monitor, and then press the power button on the monitor. Ubuntu login menu shows up.

Again, If I disconnect the HDMI cable before turning the computer on, then connect it after POST, I don't have to press power button on the computer monitor (on/off).

Edit: I solved it. CSM had to be enabled. This displayed 4 new options. For Ubuntu, UEFI only is required for boot device control. 2nd and 3rd option were set to ignore, and the 4th option, boot from PCI-E/PCI expansion device, is set to UEFI drive.