Question HDMI port not working on graphics card which has both DP and HDMI ports ?

[TiluChris]

Hello All

I have just finished building up a new compy.

Hardware as follows:
CPU: AMD Ryzen 5 5600X
MB: Gigabyte Aorus B550 Elite AX V2
GPU: Sapphire Pure RX 7800 XT
RAM: G.skill Trident Z 2 x 16GB (DDR4 3200)
SSD: Samsung 990 Pro
CPU Cooler: Corsair iCUE H150i Elite Cappelix XT
Casing: Fractal POP XL
PSU: Corsair RM850X.

For now, I don't have a screen with DP ports (will arrive next week), so to set up the BIOS and install windows 11, I thought I would use a screen with HDMI ports since the graphic card has 2 of each type.

Problem:
On HDMI port, the screen doesn't detect any signal. It remains black.

What I tried up to now:
I had the same case with another computer I built up one week ago. For this other one, the solution (given by this forum) had been to unplug from the PSU one of the two GPU power cables (as in the card was powered with only one PCIe cable 2 x 4 pins). So, I tried the same with this computer now, but in this case, it didn't work like for the other one.

Question:
What else could I try?

Side note:
Worst case, I could wait until my new screen with DP entries arrive. However, I would be happy if I could install windows 11 over the weekend so thanks in advance for anyone who could help me solve the trouble.

 

[Unolocogringo]

Some cards have a specific port for post display.
Have you tried the other port?

 

[TiluChris]

I'm not sure I understand what you mean.

I can't use the either of the DP ports on the graphic card since there are no DP ports on my "old" screen, only HDMI. So I can only connect the "old" screen to one of the GPU's HDMI ports using an HDMI cable.
But the screen is not getting a signal this way.