The left Main out stopped working. Instead, there is noise (not very loud, but clearly audible). If i listen to the Main Mix using the headphone out, everything works, too. So i think this is not a routing-problem but a problem with the Output itself. The problem appeared over night, while the mixer (and the power strip) were turned off. The mixer has been bought >3 years ago, so i don’t think this is covered by warranty. Is this a known problem? Any way how i could replace the Output?
I assume your using both Left and Right main outputs.
Do the main output meters show the same level?
Try using the ALT OUT outputs, you’ll need 1/4in TRS to XLR adapter cables. Check the ALT OUT is patched to the main L R outputs.
Have you tried swapping the cables, plug the left cable into the right and right into
the left and see what happens. If the problem stays with the same left speaker the issue
is in the cable or speaker, if it moves to the Right speaker, it’s something at the mixer.