fast track ultra preamp stopped working

[LBTM]

suddenly one input of my fast track ultra stopped working properly. it's doesn't seem to have much gain and it's noisy. also when the preamp knob is turned to full the indicator turns green, something that doesn't happen with the other ones. checked with multiple mics, pad is off, warranty expired... plugging a guitar seems to work and when i turn up the preamp gain the signal gets stronger (as normally). any ideas?

 

[bryan_kilco]

I know this probably sounds stupid, but have you tried with a different mic cable?

 

[LBTM]

I know this probably sounds stupid, but have you tried with a different mic cable?

yes, i've tried multiple mics and cables.