The red light is from optical digital audio, as the 3.5mm audio port is actually a combined 3.5mm+mini-toslink port: https://en.wikipedia.org/wiki/TOSLINK#Mini-

The red light is from optical digital audio, as the 3.5mm audio port is actually a combined 3.5mm+mini-toslink port: https://en.wikipedia.org/wiki/TOSLINK#Mini-TOSLINK https://en.wikipedia.org/wiki/TOSLINK#Mini-TOSLINK You can easily get rid of it by deactivating the digital audio port. Still this problem shouldn't exist from the beginning.