Ah. Did you reinstall Windows after replacing the motherboard? That might be significant, especially if it's a slightly different motherboard. The chipset drivers in the existing Windows system may be wrong for the new motherboard. In addition, Windows configures itself at install time for the hardware platform it's going on, so if you change the platform you really should reinstall Windows.
I'm not a hardware expert so I won't comment on the voltages, but I do think a completely clean reinstall from bootable media, deleting existing UEFI partitions, is a wise next move.
