Hello.
I recently bought two ASRock B650I Lightning WiFi motherboards (from different places) to build two systems. Updated the BIOS to the latest non-beta right after I build the system.
I noticed a problem when trying to run DC fans on both of these systems.
On each system the PSU has Noctua NF-A4x20 FLX (DC) fan in them and I wanted to connect them to CPU2 or CHA1 header, and configure their curves based on CPU temps. It worked at first. But later after several days I noticed the PSU area to be unusually warm. Checked the fans - they did not spin.
After some experiments it seemed to me that the problem is that frequently the system "forgets" to power these fans on. To me it happens after sleep or shutdown (but with AC plug still inserted).
First I thought that the problem is with the curve that I set (fan not being able to spin up at that voltage). My curve starts from 60% duty cycle. So I tried to check that. During these times when the fan does spin I entered the BIOS and set the duty cycle to 0% (fan shuts down). Then after putting 60% it it, it successfully spins up. Tried several times and I can confirm that 60% for my fan is enough to start it.
Also I tried to check the actual voltage on fen header. When the system successfully powers on the fan, it reads around 7.8V on the fan header. But when the fan fails to ramp up, it says 0.0V. To me that's an indicator that so the system does not put any voltage to the header for some reason. Consequently, the fan does not start.
P. S. Also it seems that if I unplug the whole system from the AC mains, wait a minute to discharge the caps, and plug it in, it starts the fan successfully even with my curve.
What could be the problem and how to solve it? I don't want my PSU to cook itself after when mobo "forgets" to start the fan.
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