Modwright KWI 200 panel controls defective

Hi.
I have a Modwright kwi 200 where the volume and input selector at front panel are not working, or not working like intended i should say. Remote control works like normal. The panel knops will both only select either "cd" input or "bp" (bypass). If I use the remote the amp is playing like it should.
I have looked for a diagram or service manual but I find nothing...
Is there a solution for this problem, so I can fix it myself?

Thank you.
 
Last edited: