Hey guys,
so I had to swap my RM850x 2024 ATX 3.1 with an NZXT C850 Gold ATX 3.1 to get rid off extremely loud coil whine that I had with two RM850x and one RM750x. Since then the be quiet Silent Wings 4 120mm PWM that are connected to the included PWM Hub (PCB) from Corsair 5000D make a weird noise right after the PSU shuts off.
In the video (turn up to full volume) you can hear the PSU click and right after the weird fan noise. It is 100% related to the fans, because if I disconnect them from the hub, no more such noise.
I would like to know why this happens and my theory is this: The Hub is connected to one MB Fan Port and gets power via 12V Sata connector from PSU. It seems that the C850 switches off MB power a second before 12V Sata, so the fans don't get PWM signal for a brief moment but still 12V power. One second later the 12V power is shut off or has simply vanished due to capacitor discharge. If this theory makes sense, then RM850x must have shut off MB and Sata power simultaneously and therefore the fans don't make such noise.
I'm hoping someone with more tech expertise could explain to me what happens!